Better Fathers Have Smaller Testicles, But…

Posted on September 10, 2013 by Jesse Marczyk

There is currently an article making the rounds in the popular media (or at least the range of media that I’m exposed to) suggesting that testicular volume is a predictor of paternal investment in children: the larger the testicles, the less nurturing, fatherly behavior we see. I get the nagging sense that stories about genitals tends to get a larger-than-average share of attention (I did end up tracking the article down, after all), and that might have motivated both the crafting and sharing of this study (at least in the media. I can’t speak directly to the author’s intentions, though I can note the two domains often fail to overlap). In any case, more attention does not necessarily mean that people end up with an accurate picture of the research. Indeed, the percentage of people who will – or even can – read the source paper itself is vastly outnumbered by those who will not. So, for whatever it’s worth, here’s a more in-depth look at the flavor of the week research finding.

Our next new flavor will come out at the end of the month…

The paper (Mascaro, Hackett, & Rilling, 2013) begins with a discussion of life history theory. With respect to sexual behavior, life history theory posits that there is a tradeoff between mating effort and parental effort: the energy an organism spends investing in any single offspring is energy not spent in making new ones. Since then name of the game in evolution is maximizing fitness, this tradeoff needs to be resolved, and can be in various ways. Humans, compared to many other species, tend to fall rather heavily on the “investing” side of the scale, pouring immense amounts of time and energy into each highly-dependent offspring. Other species, like Salmon, for instance, invest all their energy into a single bout of mating, producing many offspring, but investing relatively less in each (as dead parents often make poor candidates for sources of potential investment). Life history theory is not just useful for understanding between-species differences though; it is also useful for understanding individual differences within species (as it must be, since the variation in the respective traits between species needed to have come from some initial population without said variance).

Perhaps the most well-known examples are the between-sex differences in life history tradeoffs among mammals, but let’s just stick to humans to make it relatable. When a woman gets pregnant, provided the baby will carried to term, her minimum required investment is approximately 9 months of pregnancy and often several years of breastfeeding, much of which precludes additional reproduction. The metabolic and temporal costs of this endeavor are hard to overstate. By contrast, a male’s minimum obligate investment in the process is a single ejaculate and however long intercourse took. One can immediately see that men tend to have more to gain from investing in mating effort, relative to women, at least from the minimum-investment standpoint. However, not all men have as much potential to achieve those mating-effort gains; some men are more attractive sexual partners, and others will be relatively shut-out of the mating market. If one cannot compete in the mating domain, it might pay to make oneself more appealing in the investment domain where they can more effectively compete. Accordingly, if one tends to attempt the investment strategy (though this need not mean a consciously-chosen plan), it’s plausible their body might follow a similar investment strategy, placing fewer resources into the more mating-orientated aspects of our physiology: specifically, the testicles.

Unsurprisingly, testicular volume appears to be correlated with a number of factors, but most notably sperm production (this especially the case between species, as I’ve written about before). Those men who tend to preferentially pursue a mating strategy (relative to an investment one) have slightly-different adaptive hurdles to overcome, most notably in the insemination and sperm competition arenas. Accordingly, Mascaro, Hackett, & Rilling (2013) predicted that we ought to see a relationship between testes size (representing a form of mating effort) and nurturing offspring (representing a form of parental effort). Enter the current study, where 70 biological fathers who were living with the mother of their children had their testicular volume (n = 55) and testosterone levels (n = 66) assessed. Additionally, reports of their parental behavior were also collected, along with a few other measures. As the title of the paper suggests, there was indeed a negative correlation (-0.29) between reported care-giving and testicle volume. This is the point where the highlighted finding begins to need qualifications, however, due to another pesky little factor: testosterone. Testosterone levels were also found to negatively correlate with reports of care-giving (-0.27), as well as the father’s reported desire to provide care (-0.26). Given that these are correlations, it’s not readily apparent that testicular volume per se would be the metaphorical horse pulling the cart.

Pulling the cart, metaphorically, “all the way“, that is.

Perhaps also unsurprisingly, testicular volume showed what the authors called a “moderate positive correlation” with testosterone levels (0.26, p = 0.06). As an aside, I find it interesting that the authors had, only a few sentences prior, reported an almost identically-sized correlation (r = -0.25, p = 0.06) between testicular volume and desire to invest in children, but there they labeled the correlation as a “strong trend”, rather than a “moderate correlation”. The choice of wording seems peculiar.

In any case, if bigger balls tended to go together with more testosterone, it becomes more difficult to make the case for testicular volume itself to be driving the relationship with parenting behaviors. In order to attempt and solve this problem, Mascaro, Hackett, & Rilling (2013) created a regression model, using testicular volume, testosterone levels, father’s earning, and hours worked as predictors of childcare. In that model, the only significant predictor of childcare was testosterone level.

Removing the “father’s earning” and “number of hours worked” variables from the regression model resulted in a gain in predictive value for testicular volume (though it was still not significant) but, again, it was testosterone that appeared to be having the greater effect. Whether or not it would be defensible to modify the regression model in that particular way in the first place is debatable, as the modification seems to be done in the interest of making testicular volume appear relatively more predictive than it was previously (also, removing those two previous factors resulted in the model accounting for quite a bit less of the variance in fathers’ overall childcare behaviors). Just because the authors had some a priori prediction about testicular volume and not about hours worked or money earned seems like only a mediocre reason for justifying the exclusion of the latter two variables while retaining the former.

There was also some neuroscience included in the study concerning the men looking at pictures of children’s faces and correlating the neural responses with childcare, testicular volume, and testosterone. I’ll preface what I’m about to say with the standard warning: I’m not the world’s foremost expert on neuroscience, so there is a distinct possibility I’m misunderstanding something here. That said, the authors did find a relationship there between testicular volume and neural response to children – a relationship that was apparently not diminished when controlling for testosterone. It should be noted that, again, unless I’m misunderstanding something, this connection didn’t appear to translate into significant increases in the childcare actually displayed by the males in the study once the effects of testosterone were considered (if it did, it should have shown up in the initial regression models). Then again, I have historically been overly-cautious about inferring much from brain scans, so take from that what you will.

I’ve got my eye on you, imaging technology…

To return to the title of this post, yes, testicular volume appears to have some predictive value in determining parental care, but this value tends to be reduced, often substantially so, once a few other variables are considered. Now I happen to think that the hypotheses derived from life history theory are well thought out in this paper. I imagine I might be inclined to have made such predictions myself. Testicular measures have already given us plenty of useful information about the mating habits of various species, and I would expect there is still value to be gained from considering them. That said, I would also advise some degree of caution in attempting to fit the data to these interesting hypotheses. Using selective phrasing to highlight some trends (the connection between testicular volume and desire to provide childcare) relative to others (the connection between testicular volume and testosterone) because they fit the hypothesis better makes me uneasy. Similarly, dropping variables from a regression model to improve the predictive power of the variable of interest is also troublesome. Perhaps the basic idea might prove more fruitful were it to be expanded to other kinds of men (single men, non-fathers, divorced, etc) but, in any case, I find the research idea quite an interesting step, and I look forward to hearing a lot more about our balls in the future.

References: Mascaro, J., Hackett, P., & Rilling, J. (2013). Testicular volume is inversely correlated with nurturing-related brain activity in human fathers. Proceedings of the National Academy of Sciences of the United States of America.

Sexed-Up Statistics – Female Genital Mutilation

Posted on June 22, 2013 by Jesse Marczyk

“A lie can travel halfway around the world while the truth is putting on its shoes” – Mark Twain.

I had planned on finishing up another post today (which will likely be up tomorrow now) until a news story caught my eye this morning, changing my plans somewhat. The news story (found on Alternet) is titled, “Evidence shows that female genital cutting is a growing phenomenon in the US“. Yikes; that certainly sounds worrying. From that title, and subsequent article, it would seem two things are likely to inferred by the reader: (1) There is more female genital cutting in the US in recent years than there was in the past and (2) some kind of evidence supports that claim. There were several facets of the article that struck me as suspect, however, most of which speak to the second point: I don’t think the author has the evidence required to substantiate their claims about FGC. Just to clear up a few initial points, before moving forward with this analysis, no; I’m not trying to claim that FGC doesn’t occur at all in the US or on overseas trips from the US. Also, I personally oppose the practice in both the male and female varieties; cutting pieces off a non-consenting individual is, on my moral scale, a bad thing. My points here only concern accurate scholarship in reporting. They also raise the possibility that the problem may well be overstated – something which, I think, ought to be good news.

It means we can start with just the pitchforks; the torches aren’t required…yet.

So let’s look at the first major alarmist claim of the article: there was a report put out by the Sanctuary for Families that claimed approximately 200,000 women living in the US were living in risk of genital cutting. That number sounds pretty troubling, but the latter part of the claim sounds a bit strange: what does “at risk” mean? I suppose, for instance, that I’m living “at risk” of being involved in a fatal car accident, just as everyone else who drives a car is. Saying that there are approximately 200,000,000 people in the US living at risk of a fatal car crash is useless on its own, though: it requires some qualifications. So what’s the context behind the FGC number? The report itself references a 1997 paper by the CDC that estimated between 150,000 and 200,000 women in the US were at risk of being forced to undergo FGC (which we’ll return to later). Given that the reference for claim is a paper by the CDC, it seems very peculiar that the Sanctuary for Families attaches a citation that instead directs you to another news site that just reiterates the claim.

This is peculiar for two reasons: first, it’s a useless reference. It would be a bit like my writing down on a sheet of paper, “I think FGC is one the rise” because I had read it somewhere, and then referencing the fact that I wrote that down when I say it again the next time.Without directing one the initial source of the claim, it’s not a proper citation and doesn’t add any information. The second reason that the reference is peculiar is that the 1997 CDC paper (or at least what I assume is the paper) is actually freely available online. It took me all of 15 seconds to find it through a Google search. While I’m not prepared to infer any sinister motivation on the Sanctuary for Families for not citing the actual paper, it does, I think speak to the quality of scholarship that went into drafting the report, and in a negative way. It makes one wonder whether they actually read the key report in the first place.

Thankfully, it does finally provide us with the context as to how the estimated number was arrived at. The first point worth noting is that the estimate the paper delivers (168,000) is a reflection of people living in the US who had either already undergone the procedure before they moved here or who might undergo it in the future (but not necessarily within the US). The estimate is mute on when or where the procedure might have taken place. If it happened in another country years or decades ago, it would be part of this estimate. In any case, the authors began with the 1990 census data of the US population. On the census, respondents were asked about their country of origin and how long they lived in the US. From that data, the authors then cross-referenced the estimated rates of FGC in people’s home countries to estimate whether or not they were likely to have undergone the procedure. Further, the authors made the assumption in all of this that immigrants were not unique from the population from which they were derived with respect to their practicing of FGC: if 50% of the population in a families’ country of origin practiced it, then 50% of immigrants were expected to have practiced it or might do so in the future. In other words, the 168,000 number is an estimate, based on other estimates, based on an assumption.

It’s an impressive number, but I worry about its foundation.

I would call this figure, well, a very-rough estimate, and not exactly solid evidence. Further, it’s an estimate of FGC in other countries; not in the US. The authors of the CDC paper were explicit about this point, writing, “No direct information is available on FGC in the United States”. It is curious, then, that the Sanctuary report and the Alternet article both reference the threat of FGC that girls in the US face while referencing the CDC estimate. For example, here’s how the Sanctuary report phrased the estimate:

In 1997, however, the Centers for Disease Control and Prevention (CDC) estimated that as many as 150,000 to 200,000 girls in the United States were at risk of being forced to undergo female genital mutilation.

See the important differences? The CDC estimate wasn’t one concerning people at risk of being forced to undergo the practice; it was an estimate of people who might undergo it and whom might have already undergone it at some point in the past in some other country. Indeed, the CDC document could more accurately be considered an immigration report, rather than an paper on FGC itself. So, when the Sanctuary report and Alternet article suggest that the number of women at risk for FGC is rising, what they appear to mean is that immigration from certain countries where the practice is more common is rising, but that doesn’t seem to have quite the same emotional effect. Importantly, the level of risk isn’t ever qualified. Approximately 200,000,000 people are “at risk” of being involved in a fatal car crash; how many of them actually are involved in one? (about 40,000 a year and on the decline). So how many of the 168,000 women “at risk” for FGC already had one, how many might still be “at risk”, and how many of those “at risk” end up actually undergoing the procedure? Good evidence is missing on these points.

This kind of not-entirely-accurate reporting remind me of a piece by Neuroskeptic on what he called “sexed-up statistics”. These are statistics presented or reported on in such a way as to make some problem seem as bad as possible, most likely in the goal of furthering some social, political, or funding goals (big problems attract money for their solution). It’s come up before in the debate over the wage-gap between men and women, and when considering the extent of rape among college-aged (and non-college aged) women, to just name two prominent cases. This ought not be terribly surprising in light of the fact that the pursuit of dispassionate accuracy is likely not the function of human reasoning. The speed with which people can either accept or reject previously-unknown information (such as the rate of FGC in the US and whether it’s a growing problem) tells us that concerns for accuracy per se are not driving these decisions. This is probably why the initial quote by Mark Twain carries the intuitive appeal that it does.

“Everyone but me and the people I agree with are so easily fooled!”

FGC ought to be opposed, but it’s important to not let one’s opposition for it (or, for that matter, one’s opposition or support for any other specific issue) get in the way of accurately considering and reporting on the evidence at hand (or al least doing the best one can in that regard). The evidence – and that term is used rather loosely here – presented certainly does not show that illegal FGC is a “growing phenomenon in the US”, as Jodie at Alternet suggests. How could the evidence even already show it was a growing problem if one grants that determining the initial and current scope of the problem hasn’t been done and couldn’t even feasibly be done? As far as the “evidence” suggests, the problem could be on the rise, on the decline, or have remained static. One of those options just happens to make for the “sexier” story; the story more capable of making its way halfway around the world in an instant.

Mathematical Modeling Of Menopause

Posted on June 15, 2013 by Jesse Marczyk

Some states of affairs are so ubiquitous in the natural world that – much like the air we breathe – we stop noticing their existence or finding them particularly strange. The effects of aging are good examples of this. All else being equal, we ought to expect organisms that are alive longer to reproduce more. The longevity/reproduction link would seem to make the previously-unappreciated question of why organism’s bodies tend to breakdown over time rather salient. Why do organisms grow old and frail, before one or more homeostatic systems start failing, if being alive tends to aid in reproduction? One candidate explanation for understanding senescence involves.considering the trade off between the certainty of the present and the uncertainty of the future; what we might consider the discount rate of life. Each day, our bodies need to avoid death from a variety of sources, such as accidental injuries, intentional injuries from predators or conspecifics, the billions of hungry microorganisms we encounter, or lacking access to sufficient metabolic resources. Despite the whole world seemingly trying to kill us constantly, our bodies manage to successfully cheat death pretty well, all things considered.

“What do we say to death? Not to..OH MY GOD, WHAT’S BEHIND YOU?”

Of course, we don’t always manage to avoid dying: we get sick, we get into fights, and sometimes we jump out of airplanes for fun. Each new day, then, brings new opportunities that might result in the less-than-desirable outcome, and the future is full of new days. This makes each day in the future that much less valuable than each day in the present, as future days come with the same potential benefits, but all the collective added risk. Given the uncertainty of the future, it follows that some adaptations might be designed to increase our chances of being alive today, even if they decrease our odds of being alive tomorrow. These adaptations may well explain why we age the way we do. They would be expected to make us age in very specific ways, though: all our biological systems ought to be expected to breakdown at roughly the same time. This is because investing tons of energy into making a liver that never breaks doesn’t make much sense if the lungs give out too easily, as the body with the well-functioning liver would die all the same without the ability to breathe; better to divert some of that energy from liver maintenance to lung function.

As noted previously, however, being alive is only useful from an evolutionary perspective if being alive means better genetic representation in the future. The most straightforward way of achieving said genetic representation is through direct reproduction. This makes human menopause a very strange phenomenon indeed. Why do female’s reproductive capabilities shut off decades before the rest of their body tends to? It seems that pattern of loss of function parallels the liver/lungs example. Further, as the use of the word ‘human’ suggests, this cessation of reproductive abilities is not well-documented among other species. It’s not that other species don’t ever lose the capacity for reproduction, mind you, just that they tend to lose it much closer to the point when they would die anyway. This adds a second part to our initial question concerning the existence of menopause: why does it seem to only really happen in humans?

Currently, the most viable explanation is known as “The Grandmother Hypothesis“. The hypothesis suggests that, due to the highly-dependent nature of human offspring and the risks involved in pregnancy, it became adaptive for women to cease focusing on producing new offspring of their own and shift their efforts towards investing in their existing offspring and grandoffspring. At its core, the grandmother hypothesis is just an extension of kin selection: the benefits to helping relatives begin to exceed the benefits of direct reproduction. While this hypothesis may well prove to not be the full story, it does have two major considerations going for it: first, it explains the loss of reproductive capacity through a tradeoff – time spent investing in new offspring is time not spent investing in existing ones. It doesn’t commit what I would call the “dire straits fallacy” by trying to get something for free, as some standard psychology ideas (like depressive realism) seem to. The second distinct benefit of this hypothesis is perhaps more vital, however: it explains why menopause appears to be rather human-specific by referencing something unique to humans – extremely altricial infants that are risky to give birth to.

A fairly accurate way to conceptualize the costs of the pregnancy-through-college years.

A new (and brief) paper by Morton, Stone, & Singh (2013) sought to examine another possible explanation for menopause: mate choice on the part of males.The authors used mathematical models to attempt and demonstrate that, assuming men have a preference for young mates, mutations that had deleterious effects on women’s fertility later in life could drift into fixation. Though the authors aren’t explicit on this point, they seem to be assuming, de facto, that human female menopause is a byproduct of senescence plus a male sexual preference for younger women, as without this male sexual preference, their simulated models failed to result in female menopause. They feel their models demonstrate that you don’t necessarily need something like a grandmother hypothesis to explain menopause. My trust in results derived from mathematical models like these can be described as skeptical at the best of times, so it should come as no surprise that I found this explanation lacking on three rather major fronts.

My first complaint is that while their model might show that – given certain states of affairs held – explanations like the grandmother hypothesis need not be necessary, they fail to rule out the grandmother hypothesis in empirical or theoretical way. They don’t bother to demonstrate that their state of affairs actually held. Why that’s a problem is easy to recognize: it would be trivial to concoct a separate mathematical model that “demonstrated” the strength of the grandmother hypothesis by making a different set of assumptions (such as by assuming that past a certain age, investments returned in existing offspring outweighed investments in new ones). Yes; to do so would be pure question-begging, and I fail to see how the initial model provided by Morton et al (2013) isn’t doing just that.

My second complaint is, like the grandmother hypothesis, Morton et al’s (2013) byproduct model does consider tradeoffs, avoiding the dire straits fallacy; unlike the grandmother hypothesis, however, the byproduct account fails to posit anything human-specific about menopause. It seems to me that the explanation on offer from the byproduct account could be applied to any sexually-reproducing species. Trying to explain a relatively human-specific trait with a non-human-specific selection pressure isn’t as theoretically-sound as I would like. “But”, Morton et al might object, “we do posit a human-specific trait: a male preference for young female mates“. A fine rebuttal, complicated only by the fact that this is actually the weakest point of the paper. The authors appear to be trying to use an unexplained-preference to explain the decline in fertility, when it seems the explanation ought to run in precisely the opposite direction. If, as the model initially assumes, ancestral females did not differ substantially in their fertility with respect to age, how would a male preference for younger females ever come to exist in the first place? What benefits would arise to men who shunned older – but equally fertile – women in favor of younger ones? It’s hard to say. By contrast, if our starting point is that older females were less fertile, a preference for younger ones is easily explained.

No amount of math makes this an advisable idea.

Preferences are not explanations themselves; they require explanations. Much like aging, however, people can take preferences for granted because of how common they are (like the human male’s tendency to find females of certain ages maximally attractive), forgetting that basic fact in the process. The demonstration that male mating preferences could have been the driving force explaining the existence of menopause, then, seems empty. The model, like many others that I’ve encountered, seems to do little more than restate the author’s initial assumptions as conclusions, just in the language of math, rather than English. As far as I can see, the model makes no testable or novel predictions, and only manages to reach that point by assuming a maladaptive, stable preference on the part of men. I wouldn’t mark it down as a strong contender for helping us understand the mystery of menopause.

References: Morton, R., Stone, J., & Singh, R. (2013). Mate Choice and the Origin of Menopause PLoS Computational Biology, 9 (6) DOI: 10.1371/journal.pcbi.1003092

He’s Climbing In Your Windows; He’s Snatching Your People Up

Posted on April 27, 2013 by Jesse Marczyk

One topic that has been addressed by evolutionary psychologists that managed to draw a good deal of ire was rape. Given the sensitive nature of the issue, the criticisms that the theorizing about it brought were largely undeserved, reflecting, perhaps, a human tendency to mistake explanation with exculpation. Needless to say, at this point, sexual assault will be the topic for examination today, so if it’s the kind of thing that bothers you to read about, I suggest clicking away. Now that the warning has been made, if you’re still reading we can move forward. There has been some debate among evolutionary-minded researchers as to whether or not there are any rape-specific cognitive adaptations in humans, or whether rape represents a byproduct of other mating mechanisms. The debate remains unresolved for lack of unambiguous predictions or data. As the available data could be interpreted as consistent with both sides of the debate, the question remains a slippery and contentious one.

So do be careful if you decide to try and pick it up.

A paper by Felson & Cundiff (2012) suggests to have found some data they say support the byproduct view for rape. While I find myself currently favoring the byproduct explanation, I also find their interpretation of the evidence they bring to bear on the matter underwhelming. I actually find their interpretation of several matters off, but we’ll get to that later. First, let’s consider the research itself. The authors sought to examine existing data on robberies committed by lone males 12 years or older where a lone female was present at the time. From the robbery data, the authors were further interested in examining the subset of them that also involved a report of sexually assault. Towards this end, Felson & Cundiff (2012) reported data from approximately 45,000 robberies spanning from 2000-2007. Of those robberies, roughly 2% of them also involved a sexual assault, yielding about 900 cases for examination. As an initial note, the 2% figure would seem to suggest, to me, anyway, that in most instances of robbery/sexual assault, the assaults tended to not be preplanned; they look more opportunistic.

From this sample, the authors first examined what effect the female victim’s age had on the likelihood of a sexual assault being reported during the robbery. As it turns out, the age of the woman was a major determinant: women at the highest risk of being assaulted were in the 15-29 age range (with the peak being within the 20-24 year old age range), where the average risk of a sexual assault was around 2.5%. Before this age range, the risk of assault is substantially lower, around 1.3%. After 29 years, the rate begins to decline, dropping markedly after 40, down to around an average of 0.5%. In terms of opportunistic sexual assaults, then, male robbers appear to target women in their fertile years at disproportionate frequencies, presumably partially or largely on the basis of victim’s physical attractiveness. This finding appears consistent with previous work that had found the average age of a female who was the victim of a robbery alone was 35, while the average age of a robbery/assault victim was 27.9; about 7 years of difference. Any theories of rape that assume the act is motivated by power and not by sex would seem to have a very difficult time accounting for this pattern in the data.

Next, the authors turned their attention towards characteristics of the male robbers that predict whether or not an assault was reported. The results showed that the likelihood of a sexual assault increased as the males reached sexual maturity and steadily increased further until about their mid-thirties, after which they began to decline. Further, regardless of their age, the robbers didn’t show much in the way of variance in terms of the age of women they tended to target. That is to say whether the man was in his late teens or his late forties, they all seemed to preferentially target younger women nearer to their peak fecundity. The one exception to this pattern were the males aged 12-17, who seemed to even more disproportionately prefer women in their teens and early twenties. Felson & Cundiff (2012) note that this pattern of preferences is not typically observed in consensual relationships, where men and women tend to pair up around similar ages. This suggests that older men’s patterns of engaging in relationships with older women likely represents the relative aversion of younger women to the older males; not a genuine preference on the part of men for older women per se.

Though it’s difficult to imagine why older men aren’t preferred…

That’s not to say that older men may not have a preference for pursing relatively older women, just that such a preference wouldn’t be driven by the woman’s age. Such a preference might well be driven by other factors, however, such as the relative willingness of a woman to enter into a relationship with the man in question. There’s not much point for a man in pursuing women they’re unlikely to ever attain success with, even if those women are highly attractive; better to spend that time and energy in domains more liable to payoff. Louis C.K. sums the issue up neatly in one of his stand-up routines: “to me, you’re not a woman until you’ve had a couple of kids and your life is in the toilet…[if you're a younger girl] I don’t want to fuck you…[alright] I do want to fuck you, but you won’t fuck me, so fuck you”. When such tradeoffs can be circumvented – as is the case in sexual assault – a person’s underlying preferences for certain characteristics can be more readily assessed.

This brings us to my complaints with the paper. As I mentioned initially, there’s an ongoing debate as to whether or not men have cognitive mechanisms designed for rape specifically, or whether rape is generated as a byproduct of mechanisms designed for other purposes. Felson & Cundiff (2012) suggest that their data support the byproduct interpretation. Why? Because they found that women in the 15-29 age range who were sexually assaulted were less likely to be raped than older women. This pattern of data is supposed to support the byproduct hypothesis because, I think, the authors are positing some specific motivation for sex acts that could result in conception, rather than some more general interest in sexual behavior. It’s hard to say, since the authors fail to lay out the theory behind their hypothesis with precision. This strikes me as somewhat of a strange argument, though, as it would essentially posit that sexual acts that are unlikely to result in conception (such as oral or anal sex) are motivated by a different set of cognitive mechanisms that an interest in vaginal sex. While that might potentially be the case, I’ve never seen a case made for it, and there isn’t a strong one to be found in the paper.

The other complaint I have is that the authors use a phrase that’s a particular pet peeve of mine: “..our results are consistent with the predictions from evolutionary psychology”. This phrase always troubles me because evolutionary psychology, as field, does not make a set of uniform predictions about sexual behavior. Their results may well be consistent with some sub-theories derived by psychologists using an evolutionary framework – such as sexual strategies theory – but they are not derived from evolutionary psychology more broadly. To say that a result is consistent or inconsistent with evolutionary psychology is to imply that such a finding supports or fails to support the foundational assumptions of the field; assumptions which have to do with the nature of information processing mechanisms. While this might seem like a minor semantic point at first, I feel it’s actually a rather deep issue. It’s a frequent mistake that many of evolutionary psychology’s critics make when attempting to write off the entire field on the basis of a single idea they don’t like. To the extent that such inaccurate generalizations serve to hinder people’s engagement with the field, there’s a problem to be addressed.

And if you’re not willing to engage with me, I’d like the ring back.

As evolutionary psychology more broadly doesn’t deliver specific predictions about rape, neither the hypothesis that rape is an adaptation or a byproduct should rightly be considered the official evolutionary psychology perspective on the topic; this would be the case regardless of whether the evidence strongly supported one side or the other, I might add. While the the current research doesn’t speak to either of these possibilities distinctly, it does manage to speak against the idea that rape isn’t about sex, adding to the already substantial evidence that such a view is profoundly mistaken. Of course, the not-sex explanation was always more of a political slogan than a scientific one, so the lack of empirical support for it might not prove terribly troubling for its supporters.

References: Felson, R., & Cundiff, P. (2012). Age and sexual assault during robberies Evolution and Human Behavior, 33 (1), 10-16 DOI: 10.1016/j.evolhumbehav.2011.04.002

Mothers And Others (With Benefits)

Posted on April 11, 2013 by Jesse Marczyk

Understanding the existence and persistence of homosexuality in the face of its apparently reproductive fitness costs has left many evolutionary researchers scratching their heads. Though research into homosexuality has not been left wanting for hypotheses, every known hypothesis to date but one has had several major problems when it comes to accounting for the available data (and making conceptual sense). Some of them lack a developmental story; some fail to account for the twin studies; others posit benefits that just don’t seem to be there. What most of the aforementioned research shares in common, however, is its focus: male homosexuality. Female homosexuality has inspired considerably less hypothesizing, perhaps owing to the assumption, valid or not, that female sexual preferences played less of a role in determining fitness outcomes, relative to men’s. More precisely, physical arousal is required for men in order for their to engage in intercourse, whereas it is not necessarily required for women.

Not that lack of female arousal has ever been an issue for this fine specimen.

A new paper out in Evolutionary Psychology by Kuhle & Radtke (2013) takes a functional stab at attempting to explain some female homosexual behavior. Not the homosexual orientations, mind you; just some of the same-sex behavior. On this point, I would like to note that homosexual behavior isn’t what poses an evolutionary mystery anymore than other, likely nonadaptive behaviors, such as masturbation. The mystery is why an individual would be actively averse to intercourse with members of the opposite sex; their only path to reproduction. Nevertheless, the suggestion that Kuhle & Radtke (2013) put forth is that some female homosexual sexual behavior evolved in order to recruit female alloparent support. An alloparent is an individual who provided support for an infant but is not one of that infant’s parents. A grandmother helping to raise a grandchild, then, would represent a case of alloparenting. On the subject of grandmothers, some have suggested that the reason human females reach menopause so early in their lifespan – relative to other species who go on with the potential to reproduce until right around the point they die – is that grandmother alloparenting, specifically maternal grandmother, was a more valuable resource at the point, relative to direct reproduction. On the whole, alloparenting seems pretty important, so getting a hold of good resources for the task would be adaptive.

The suggestion that women might use same-sex sexual behavior to recruit female alloparental support is good, conceptually, on at least three fronts: first, it pays some mind to what is at least a potential function for a behavior. Most psychological research fails to think about function at all, much less plausible functions, and is all the worse because of it. The second positive part of this hypothesis is that it has some developmental story to go with it, making predictions about what specific events are likely to trigger the proposed adaptation and, to some extent, anyway, why they might. Finally, it is consistent with – or at least not outright falsified by – the existing data, which is more than you can say for almost all the current theories purporting to explain male homosexuality. On these conceptual grounds, I would praise the lesbian-sex-for-alloparenting model. On other grounds, both conceptual and empirical, however, I have very serious reservations.

The first of these reservations comes in form of the source of alloparental investment. While, admittedly, I have no hard data to bear on this point (as my search for information didn’t turn up any results), I would wager it’s a good guess that a substantial share of the world’s alloparental resources come from the mother’s kin: grandparents, cousins, aunts, uncles, siblings, or even other older children. As mentioned previously, some have hypothesized that grandmothers stop reproducing, at least in part, for that end. When alloparenting is coming from the female’s relatives, it’s unlikely that much, if any, sexual behavior, same-sex or otherwise, is involved or required. Genetic relatedness is likely providing a good deal of the motivation for the altruism in these cases, so sex would be fairly unnecessary. That thought brings me neatly to my next point, and it’s one raised briefly by the authors themselves: why would the lesbian sex even be necessary in the first place?

“I’ll help mother your child so hard…”

It’s unclear to me what the same-sex behavior adds to the alloparenting equation here. This concern comes in a number of forms. The first is that it seems adaptations designed for reciprocal altruism would work here just fine: you watch my kids and I’ll watch yours. There are plenty of such relationships between same-sex individuals, regardless of whether they involve childcare or not, and those relationships seem to get on just fine without sex being involved. Sure, sexual encounters might deepen that commitment in some cases, but that’s a fact that needs explaining; not the explanation itself. How we explain it will likely have a bearing on further theoretical analysis. Sex between men and women might deepen that commitment on account of it possibly resulting in conception and all the shared responsibilities that brings. Homosexual intercourse, however, does not carry that conception risk. This means that any deepening of the social connections homosexual intercourse might bring would most likely be a byproduct of the heterosexual counterpart. In much the same way, masturbation probably feels good because the stimulation sexual intercourse provides can be successfully mimicked by one’s hand (or whatever other device the more creative among us make use of). Alternatively, it could be possible that the deepening of an emotional bond between two women as the result of a sexual encounter was directly selected for because of it’s role in recruiting alloparent support, but I don’t find the notion particularly likely.

A quick example should make it clear why: for a woman who currently does not have dependent children, the same-sex encounters don’t seem to offer her any real benefit. Despite this, there are many women who continue to engage in frequent to semi-frequent same-sex sexual behaviors and form deep relationships with other women (who are themselves frequently childless as well). If the deepening of the bond between two women was directly selected for in the case of homosexual sexual behavior due to the benefits that alloparents can bring, such facts would seem to be indicative of very poor design. That is to say we should predict that women without children would be relatively uninterested in homosexual intercourse, and the experience would not deepen their social commitment to their partner. So sure, homosexual intercourse might deepen emotional bonds between the people engaging in it, which might in turn effect how the pair behave towards one another in a number of ways. That effect, however, is likely a byproduct of mechanisms designed for heterosexual intercourse; not something that was directly selected for itself. Kuhle & Radtke (2013) do say that they’re only attempting to explain some homosexual behavior, so perhaps they might grant that some increases in emotional closeness are the byproduct of mechanisms designed for heterosexual intercourse while other increases in closeness are due to selection for alloparental concerns. While possible, such a line of reasoning can set up a scenario where the hits for the theory can be counted as supportive and the misses (such as childless women engaging in same-sex sexual behaviors) dismissed as being the product of some other factor.

On top of that concern, the entire analysis rests on the assumption that women who have engaged in sexual behavior with the mother in question ought to be more likely to provide substantially better alloparental care than women who did not. This seems to be an absolutely vital prediction of the model. Curiously, that prediction is not represented in any of the 14 predictions listed in the paper. The paper also offers no empirical data bearing on this point, so whether homosexual behavior actually causes an increase in alloparental investment is in doubt. Even if we assume this point was confirmed however, it raises another pressing question: if same-sex intercourse raises the probability or quality of alloparental investment, why would we expect, as the authors predict, that women should only adopt this homosexual behavior as a secondary strategy? More precisely, I don’t see any particularly large fitness costs to women when it comes to engaging in same-sex sexual behavior but, under this model, there would be substantial benefits. If the costs to same-sex behavior are low and the benefits high, we should see it all the time, not just when a woman is having trouble finding male investment.

“It’s been real, but men are here now so…we can still be friends?”

On the topic of male investment, the model would also seem to predict that women should be relatively inclined to abandon their female partners for male ones (as, in this theory, women’s sexual interest in other women is triggered by lack of male interest). This is anecdotal, of course, but a fairly-frequent complaint I’ve heard from lesbians or bisexual women currently involved in a relationship with a woman is that men won’t leave them alone. They don’t seem to be wanting for male romantic attention. Now maybe these women are, more or less, universally assessing these men as being unlikely or unable to invest on some level, but I have my doubts as to whether this is the case.

Finally, given these sizable hypothesized benefits and negligible costs, we ought to expect to see women competing with other women frequently in the realm of attracting same-sex sexual interest. Same-sex sexual behavior should be expected to not only be cross-cultural universals, but fairly common as well, in much the same way that same-sex friendship is (as they’re hypothesized to serve much the same function, really). Why same-sex sexual interest would be relatively confined to a minority of the population is entirely unclear to me in terms of what is outlined in the paper. This model also doesn’t deal why any women, let alone the vast majority of them, would appear to feel averse to homosexual intercourse. Such aversions would only cause a woman to lose out the hypothesized alloparental benefits which, if the model is true, ought to have been substantial. Women who were not averse would have had more consistent alloparental support historically, leading to whatever genes made such attractions more likely to spread at the expense of women who eschewed it. Again, such aversions would appear to be evidence of remarkably poor design; if the lesbian-alloparents-with-benefits idea is true, that is…

References: Kuhle BX, & Radtke S (2013). Born both ways: The alloparenting hypothesis for sexual fluidity in women. Evolutionary psychology : an international journal of evolutionary approaches to psychology and behavior, 11 (2), 304-23 PMID: 23563096

Reactions To Reactions About Steubenville

Posted on April 4, 2013 by Jesse Marczyk

Around the middle of last month, CNN came under some social-media fire. The source of this fire came from the perception among some people that CNN had covered the Steubenville rape case inappropriately. More precisely, the outrage focused on the notion that CNN had not demonized the two convicted male teens enough; if anything, many people seemed to feel that CNN had humanized the pair. Here’s one of the major quotes that people took issue with:

”It was incredibly emotional—incredibly difficult even for an outsider like me to watch what happened as these two young men that had such promising futures, star football players, very good students, literally watched as they believe their life fell apart.”

The issue, it would seem, is that many people felt that it ought not have been hard emotionally for the reporter to witness the event; if anything, she should have been angry that the teens were not sentenced more harshly. Other debates raged on in the comments sections of various articles about whether being placed on the list of registered sex offenders for the rest of their life was too harsh of a punishment for the two teens on the one hand, with those advocating the castration or death of the teens on the other extreme. I think these reactions, along with the case itself, happen to highlight some of the adaptive problems that bystanders face surrounding the moral judgments they make.

And now, since there are two degrees of separation between the tragic event and my use of it, it’s acceptable.

The first of these problems highlighted by the story is that third-party condemners (those who are not directly involved) need to pick a side in a moral dispute, and being on the wrong side of that dispute can be costly. Accordingly, third party condemners face the problem of figuring out how to coordinate their condemnation with other third parties (DeScioli & Kurzban, 2013). The problem runs deeper than choosing a side, though. As people’s reactions to the CNN story show us, even being on the “right” side of the dispute can be costly, provided one isn’t on the “right” side in the “right” way. Just to be clear, the first “right” in the previous sentence refers to being on the side with more social support; the second “right” refers to the agreement within a given side as to what the appropriate response of its members ought to be. The CNN coverage described the crime as “very serious” and the teen who was raped as “the victim”, suggesting that the reporters were certainly not of the opinion that rape is good or the boys were the real victims. The outrage was that the reporters for CNN did not appear to be appropriately outraged at the boys or offended enough on the part of the victim. CNN’s crime was not treating the teens as viciously as others would have liked.

It would seem that not condemning a behavior thoroughly enough can be interpreted by some as actually condoning that same behavior. Indeed, it was likely when the reporter for CNN said that it was emotionally difficult for her to witness the scene that she sparked the subsequent outcry against the network. This leaves us with a somewhat standard question: why should this be the case? Imagine for a moment that we’re not talking about rape anymore, but about theft. You and I both agree that stealing is wrong and deserves to be punished. However, while you think that stealing a car deserves a sentence of five years in jail and a permanent brand that says “car thief”, I think that stealing a car deserves a sentence of a year in prison and no brand. It would seem silly to conclude that, from these differences in opinion on the extent of deserved punishment, that only one of us is actually against stealing while the other is a morally condemnable “stealing-apologist”. Yet this is precisely what we see happening. Why?

A potential answer comes in more than one part. The first part of this answer is to note that, in cases of moral condemnation, the activity of certain parts of the brain associated with empathy seem to be inhibited. A neuroscience paper by Singer et al (2006) examined the responses of 16 men and 16 women in an fMRI to viewing confederates receiving painful shocks. Before the viewing took place, however, the confederates had either behaved fairly or unfairly towards the subject in a trust game. The results of the analysis found that men, but not women, showed a reduction in activation of presumably empathy-related regions of the brain when viewing the confederates receiving the painful shocks; in the case of the fair player receiving the shocks, subject’s brains showed more signs of empathy-related activation. Similarly, men, but not women, showed increases in brain regions associated with reward when the unfair player received the shocks. Post fMRI measures confirmed that men were more interested in seeking revenge against unfair players

Sure; the research could have been done without the expensive fMRI, but then we wouldn’t get pictures.

There are a few shortcomings of the Singer et al (2006) study to bear in mind as it relates to the current questions: the sample size wasn’t terribly impressive, but sample sizes in neuroscience studies seldom seem to be. The second piece to bear in mind is that these brain scans do not necessarily add much (or any) value beyond what the far cheaper survey did. At best, the brain scans were icing on the explanatory cake. Further, this study only examined cases of direct revenge, or second-party involvement; not the reactions of bystanders to the fair or unfair behavior. Nevertheless, the results hint at something interesting: the amount of empathy that people (at least men) feel towards the suffering of a perpetrator (i.e. how much they care about the consequences of the punishment to the perpetrator) might be indicative of how morally wrong they view the behavior as being, at least to some extent. One requires certain assumptions to make that leap, but it doesn’t seem too unreasonable.

The picture is not nearly that simple, however. It is at this point that the discoordination problem that DeScioli & Kurzban (2013) raised again rears its head. It is unlikely to be adaptive for condemners to completely – or partially – inhibit their empathic responses towards the perpetrator in all moral cases. While the inhibition might be adaptive in terms of avoiding the condemnation of other condemners (i.e. not being labeled a rape apologist and subsequently socially shunned), it also carries costs, chief among which is that the perpetrator often has social supporters as well. If a condemner has completely inhibited such empathic systems, they’re likely to seek greater punishments of the perpetrators which, by extension, are also punishments leveled against the perpetrator’s social allies. To put the matter more plainly, if my friend goes to jail, I’m out a friend and worse off for it. This can lead to retaliation on the part of the perpetrator’s allies: case in point, it was not long after the verdict was handed down that the rape victim received two threats from other girls who seemed to be socially aligned with one or more of the perpetrators.

This puts third parties in an unpleasant situation: no matter who they side with, they’re likely to face some condemnation, either for condemning one party too much or not condemning that party enough. Similarly, if the third party happens to be socially connected with either the perpetrator or the victim, any harms that befall that party are, by proxy, harms that befall the third parties themselves. Thus, inhibiting an empathy reaction towards a perpetrator might entail the related need to inhibit empathy towards the perpetrator’s social allies, at least to some degree. Such a need could potentially expand the costs associated with the conflicts surrounding moral condemnation and punishment, as the number of people to be punished has grown beyond the initial disputants. The fact that the coordination problem is actually a series of many different problems makes the matter of third-party coordination all the trickier to solve. In fact, it would seem that in many cases, perhaps even most cases, it is not at all clear that people actually do manage to consistently solve the coordination problem.

The whole mess makes dueling seem like a more reasonable alternative.

The previous analysis puts the matter as to why ostensible third parties become involved in moral disputes into a new light. Getting involved in these disputes is clearly a potentially costly endeavor, so why would an uninvolved party bother getting involved in the first place? What are the benefits to joining in the disputes of others that offset these very real costs? Part of that answer would seem to be that these third parties, as previously mentioned, are indirectly personally affected by their outcomes: my friend being condemned or harmed is bad for me to the extent that the condemnation or harm prevents them from delivering me benefits they previous did or potentially might. Further still, if a friend of a friend has been affected in some way it is still potentially detrimental to me. The extent of that detriment would, of course, decrease as social distance between the parties increased; my best friend’s friend is more valuable to me than my acquaintance’s friend. A final possibility is that my not siding with one side could be taken as implicit support for the opposing side, making me the target of moral condemnation by assoication. The result of that perception of implicit support being that it can be similarly costly to me to not become involved. In other words, saying that one doesn’t care at all about the perpetrators or the victim in the Steubenville case is unlikely to earn you many friends, but it will likely still earn you plenty of condemnation.

References: DeScioli P, & Kurzban R (2013). A solution to the mysteries of morality. Psychological bulletin, 139 (2), 477-96 PMID: 22747563

Singer, T., Seymour, B., O’Doherty, J., Stephan, K., Dolan, R., & Frith, C. (2006). Empathic neural responses are modulated by the perceived fairness of others Nature, 439 (7075), 466-469 DOI: 10.1038/nature04271

A New Theory For Homosexuality: A Lot Like The Old Ones

Posted on March 16, 2013 by Jesse Marczyk

Homosexuality – male homosexuality in particular – poses a real evolutionary mystery that researchers have been trying to solve for at least the past two decades without much success. Though many explanations have been put forth to try and find the hidden fitness benefits that might allow male homosexuality to persist in the substantial minority of the population that it does despite the substantial fitness costs to the sexual preference, all the adaptive explanations have been left wanting. Decades of failed research has not seemed to have deterred new hypothesizing, though. For better or worse, I find the tenacity of the adaptive hypotheses for homosexuality to be fascinating: it is as if people cannot accept, or even consider the possibility, that homosexuality might not carry any reproductive benefits, hidden, indirectly, or otherwise. Were other key adaptations (that are not sexual orientation) to fail to develop in an adaptive fashion early in life – such as vision or hearing – I don’t think many people would be trying to find the hidden reproductive benefits or functions to being blind or deaf. The causes, certainly, but not the benefits.

“But what if being blind caused him to invest more in kin…?”

On the subject, there’s a new paper out in Evolution and Human Behavior (Barthes, Godelle, & Raymond, 2013: H/T to Dan) that, again, asks whether there might be some hidden fitness benefit associated with male homosexuality. In this case, the focus of the benefits are the female sisters of male homosexuals. The theory goes like this: after the advent of agriculture, social classes began to take root as large quantities of resources could now be generated and defended. Women could thus gain some reproductive advantage were they able to pair with men of higher social status who had these resources; a preference for doing so is known as hypergyny. However, only a small proportion of these pairings occur across social classes: women of higher social classes tended to marry men of higher social classes, and likewise for the lower classes. Accordingly, any trait that could help women mate upwards in the social ladder would have been selected for, even if it came at some expense to male reproductive fitness.

So, in this theory, male homosexual preference is a byproduct of females being able to better pursue their hypergynous inclinations. The male reproductive disadvantage from developing a homosexual preference would be more than offset by the presumed increases to female fertility and/or attractiveness to higher-status males. One distinct advantage that the authors feel this theory has is its ability to explain why male homosexual preference seems to be exclusively human (the one notable exception might be rams, a species with a history of co-residence with humans). Since male homosexuality only came to be after the advent of agriculture, long-term pair bonds, and the establishment of social classes, which other species tend to not have, this helps explain why we don’t see sexually-antagonistic male homosexuality in other species. It’s a neat idea, but neatness alone doesn’t win the day in the world of science, so let’s move on to consider what data they bring to bear on this hypothesis.

The first piece of “evidence” they present in support of this hypothesis is a mathematical model attempting to demonstrate the conditions under which such a genotype could come to exist. I’ve previously made my stance on the usefulness of such models rather explicit, but I’ll restate it here in a sentence: these models are philosophical intuitions written in the form of math, rather than English (or the language of your choice), and can be used to demonstrate literally anything. Since the models are only as good as their match to reality, my concern is, justifiably, on the extent of that match rather than the model itself. The evidence presented in terms of said match is an examination of the anthropological record of 48 societies to find out where the presence of homosexuality has been recorded, where it seems to be absent, and where it might exist. Further, these societies were also assessed in terms of how socially stratified they were, and these results were compared to the presence of male homosexual preference. The results showed that increasing social stratification was correlated with a increases in finding the presence of male homosexual preference.

Does the income disparity in America see a little…gay…to you?

When it comes to the social stratification hypothesis, should you not believe the hype, or does it bring the noise? We can begin by noting that the empirical support here is extremely weak. The paper doesn’t test to see whether more social stratification leads to more homosexuality; it merely examines whether societies that are socially stratified are more likely to have homosexual preference present or absent. Such a correlation is unlikely to be very informative, much less establish any kind of causation. Second, the paper didn’t bother to examine whether the female relatives of male homosexuals tended to actually be any more likely to marry up, or be more fertile, or be more attractive, which seems like necessary components of this model. Positing design features in a trait and then not bothering to see if those design features are present seems like poor research design. Those two points are, however, only the two things the authors talked about and didn’t test: there are also points the authors fail to mention, which I think have a strong bearing on their hypothesis.

The first of these points is that the paper makes no mention of the genetic data showing that monozygotic male twins are only concordant for a homosexual orientation around 30% of the time. This means that though the authors suggest some genes might make it more likely that a male develops a homosexual orientation, they fail to specify precisely which factors are important for developing one and why some twins fail to end up with the same orientation. So that leaves no mention of the genetic data, no mention of a developmental story, and no good test of the paper’s main contentions. I’m not sure to what extent this lack of any good empirical tests is the result of the paper’s reliance on a mathematical model, but I will note that, in my personal experience, there seems to a correlation between generating these models and poorly supporting them empirically.

There is, however, one final point I would like to mention that the authors don’t seem to really make any mention of. Part of their model requires that females have a preference for hypergyny but, in order for this preference to exist, it requires differences in social status to exist. After all, you can’t select mates on a non-existent criteria. If the authors are postulating, which they seem to be, that such a mate criteria didn’t exist in force before the advent of agriculture, it begs the question as to where this female mate preference for higher status men came from in the first place. This would require one of two things for the model: first, either that agriculture arose, followed by the female mate preference, followed by male homosexual preference, which is an awful lot to ask of 10,000 years.

Alternatively, one could argue, that differences in male status and its effect on female fitness likely predated agriculture and, further, that this preference might have been exaggerated to some degree and in some places in relative recent time periods. This would imply, in terms of the social stratification model, that the selection pressures responsible for generating the conditions for homosexuality were already in existence beforehand, so homosexuality is likely older than agriculture. If that is the case, then evolution would have had much more time to strip out the deleterious effects of any sexually antagonism. So, really, neither answer to this last concern bodes well for the model.

At least they had a mathematical model, which really saved things…

As I initially stated, I find the emphasis that people place on finding an adaptive explanation for homosexuality to be a bit curious. I would like to add that I also find the emphasis that some people are willing to place on mathematical models curious as well. There are a not insignificant percentage of academics who seem to find mathematical models to be impressive despite many cases, like this one, where they don’t seem to add much to the discussion. I get the impression that if these models were written in English, rather than math, people would be far less swayed by them, as it would make clear precisely how much many of them appear to just assume or ignore. Once the assumptions are stripped away, all this paper seems to add is a correlation between social stratification and the mere existence of homosexuality. Then again, it seems to persuade the reviewers to publish it, so maybe there’s something I’m missing…

References: Barthes, J., Godelle, B., & Raymond, M. (2013). Human social stratification and hypergyny: toward an understanding of male homosexual preference Evolution and Human Behavior DOI: 10.1016/j.evolhumbehav.2013.01.001

Tropes Against Video Games

Posted on March 9, 2013 by Jesse Marczyk

Back in mid-May of last year, Anita Sarkeesian launched a Kickstarter project to help fund her video series on portrayals of women in video games called “Tropes vs. Women in Video Games”. Her initial goal was set at $6000 for a planned goal of making 5 videos (or so I can gather from the Kickstarter page), meaning that she wanted approximately $1200 per video. Her project ended up being funded at close to $160,000 and her intent grew to creating 12 videos. This means that, currently, she has successfully netted a little over $13,000 per video she intends to eventually release; an impressive feat. Her first video was released a few days ago (a few months late, relative to her stated delivery, but here nonetheless) and, hot-button topic that her project was, I felt inclined to watch it and see what $13,000 a video buys in terms of research quality, methodology, and explanatory power. From my impression of Anita’s first video, were I to work under the assumption that she was making a reasonable amount of money for her time, effort, and conclusions in this project, I think I could be so bold as to suggest that I’m wildly underpaid for what I do in terms of research and writing.

I may not be as well-paid, but I make up for it in smug self-satisfaction.

Since Anita suggests that it’s important to think critically about the more problematic aspects of things (in this case, the “damsel in distress” story found in some video games), I’m sure she would agree it would be important to think critically about what she presents in her first video, so let’s do just that. The gist of the video appeared to be that, as noted, women are sometimes portrayed as being placed into peril (typically by a male character) from which a male character saves them. How common are such portrayals in video games? That’s an excellent question; perhaps Anita could have mentioned some data that bear on the point. Are these portrayals more or less common in video games, relative to other forms of media, and have they been getting more or less common over time? Those are some other excellent questions, but you won’t find any discussion of them either. Of course, this was only part 1 of the video, so maybe Anita’s saving all of her research findings for part 2. After all, it would surely seem peculiar if, after asking for several thousand dollars to make these videos that she claimed would take her a substantial amount of time and research, she ended up releasing videos stating her preexisting opinions about the matter, putting very little actual research in. Peculiar indeed.

The first set of points that I would be critical about when evaluating this video, then, is that, in the roughly 25 minutes of it, she presents almost nothing that would typically fall under the umbrella of what many people would consider research: there’s no methodology mentioned, no data presented, and there’s no discussion of how she reached the conclusions that she does. What she does present are some anecdotes and a few assertions. Here’s a good for-instance: Anita notes that the theme of “man-saving-woman” is at least several thousand years old. Despite noting this, she then goes on to suggest that, in 1933, there were two things (Popeye and King Kong, apparently) that led to this theme becoming a foundational element in video games 50 years later. Is this theme a foundational element in gaming? Maybe, but from what Anita presents in her video there’s no way to know (a) what she means by “foundational element”, (b) whether she was correct in that assessment, or (c) whether her posited causal link even exists. That is, if Popeye and King Kong never existed, would video games have come to represent this damsel in distress story line as frequently or infrequently as they do? Given that this theme is at least as old as recorded history accordingly to Anita, one could reasonably suggest that Popeye and King Kong did very little stage-setting at all.

What is notably absent from Anita’s video – on top of any mention of methodology or data – is any attempt at an explanation as for why this theme appears to be relatively ubiquitous. Lacking anything resembling a formal explanation concerning this theme’s popularity, much less any attempts at ruling out alternative explanations, Anita sticks largely to just noting that the theme exists in some unspecified proportion of games and that she doesn’t seem to like it very much. So, to recap, that’s no mention of a method, findings, or an explanation of the topic being investigated. Of course, I’m not here to just be critical of the fact that this video likely cost her backers approximately $260 per minute to make, by my estimation, and ended up with nothing of value to show for it; I also want to see if whether, in a few minutes, I can do better than Anita in discussing important questions, analyzing data, and explaining the issues.

“On your mark, get set…Hey, how come only men are racing in this picture?!”

So why might it be that it’s typically men who are portrayed as the saver of the woman, rather than the reverse? Why might it be that men are portrayed as predominately trying to save women, rather than other men? In order to answer those questions, it is helpful to first consider a third question: why is it the case that when a species of animal has one sex that displays a costly ornament – like peacocks – or one sex that engages in costly competition – like bowerbirds or rams – that this sex is most frequently the males? Here’s one candidate explanation that doesn’t work: peacocks have evolved such decorative plumes that they display for peahens in order to reduce the peahens to mere objects. The display itself serves the function of reducing peahens to powerless objects so that male peacocks can thus be empowered protagonists in their own male power fantasies. Though this explanation might sound silly on the grounds that you think that peacocks and peahens don’t think that way, there’s a better reason for discounting such an explanation: objectifying one sex to empowering the other doesn’t do anything biologically useful. As the explanation stands, it’s incomplete at best. Rather than explaining the phenomenon in question, the explanation phase is just pushed back one step to: why would peacocks benefit by objectify peahens? Where’s the reproductive payoff for a psychology that did that?

Here’s an altogether more plausible alternative explanation: peacocks have evolved this trait and display it because peahens were more inclined to mate with males that had larger, costlier, and harder-to-fake signals of phenotypic quality (Zahavi, 1975). Peahens favored such males because these costly signals served as viable reproductive guarantees of healthy offspring, and male behavior and physiology changed to suit the preferences of females so as to capitalize on the increased potential for reproduction. Peacocks behave this certain way, then, to attract mates; not to objectify or disempower them. To couch this in terms of a specific video game example Anita mentions, Mario doesn’t rush into Bowser’s castle in order to reduce Princess Peach to a helpless object; he does so because, by doing so, he’s increasing the chances he’ll have the opportunity to have or maintain a relationship with her (though whether or not this is his conscious motivating drive is a separate question).

With this explanation in mind, let’s do our best to imagine that peacocks and peahens decided to do distinctly human-like things, such as fantasizing and telling stories. What would the content of such things tend to be,? It seems that the sex of the individual in question would matter a great deal: the males might be enthralled by imagining tales of conflicts between other males with impressive ornaments, both displaying them for a desired female, and fantasize about displaying such an impressive ornament that the female who observed it couldn’t help but fall madly in love with him. Females, on the other hand, might find stories about other females deciding between their various competitors to be altogether more engaging, fantasizing about the social intricacies of deciding upon one male or another. You could think the distinction being something along the lines of the peacocks enjoying movies more along the lines of Die Hard and peahens being more inclined towards Twilight. Both stories involve a good deal of male-male competition, but the focus of the story would either center on the male or female perspective in that competition.

Let’s finally assume that this species of bird came across the technological capabilities to translate their fantasies into video games. Arguably, it’s easier to translate certain aspects of the the typical male fantasy into something resembling a video game that’s entertaining to play. While one could easily imagine a game where a peacock moves from level to level by out-competing his rivals, it’s less easy to imagine a game centered around female choice of partners (more succinctly, while Twilight might make an appealing series of books and movies, it might not make a good video game). Tying this back to Anita’s video, she seems to suggest that male video game designers are trying to tap into male power fantasies to sell more video games and, importantly, that they do this to the exclusion of women. What she did not seem to consider are two alternative explanations: (1) how easily are typically male and female fantasies turned into entertaining video games and/or (2) are the people making these games simply expressing their own preferences for what they find appealing, rather than trying to explicitly appeal to the preferences of others? Regarding that second point, imagine asking men to write a story that they were either trying to sell or not sell: would the content of these stories between the two groups differ significantly in terms of major themes, like the use of a damsel in distress? Certainly an interesting question: perhaps it’s one that Anita might have considered answering…

Or, you know, she could just take pictures in front of video games; that works too.

So we now have the beginnings of a plausible explanation for understanding the first question (why are men typically rescuing women, rather than the reverse) and have considered some alternative explanations as to why such a theme might be as common as it is across time and genres. It might not be too much, but it’s at least a start, providing us with some considerations that help us interpret the meager amount of information Anita offers.

To conclude, let’s briefly consider further why some of Anita’s beliefs about the motivations of male video game characters and designers, are, at the very least, likely in need if revision. There is another research finding that casts severe doubt on the “men view women as helpless objects in need of saving” angle that Anita seems to favor. When a mixed-sex group of 3 people was made up of 2 men and 1 woman, men were found to universally volunteer and end up in a role that caused them discomfort; what awful paternalistic sexist crap, right? Surely women could handle that discomfort just as well as the men, so men must be pushing women out of the hero role to fulfill their own power fantasies. By contrast, however, when then groups were made up of 1 man and 2 women, men ended up in this “protective” role at chance levels (McAndrew & Perilloux, 2012). So unless the hypothesis is to be amended to “men tend to view women as powerless and in need of rescue but only in the presence of other men (or, perhaps, when women are relatively scarce); oh, and also women tend feel the same way about the whole being protected by men thing”, one could conclude there’s likely some wrong with Anita’s hypothesis. If only she had done some kind of research to figure that out…

(I’d also like to note, as a bit of off-topic point, the apparent contrast between Anita’s proposed videos #4 and #9. It looks like she’s exploring the trope of women being sexy and evil in 4, and the trope of being unattractive and evil in 9, both of which are apparently unacceptable. Damned if the villainess is attractive; damned if she isn’t. But hey, only an approximate $260 per minute for this knowledge, right?)

References: McAndrew, F.T. & Perilloux, C. (2012). Is self-sacrifical competitive altruism primarily a male activity? Evolutionary Psychology, 10, 50-65

Zahavi, A. (1975). Mate selection—A selection for a handicap Journal of Theoretical Biology, 53 (1), 205-214 DOI: 10.1016/0022-5193(75)90111-3

“Nice Guys”, The Friend Zone, And Social Semantics

Posted on February 22, 2013 by Jesse Marczyk

A little over a year ago, a video entitled, “Why men and women can’t be friends” was uploaded to YouTube. In the video, a man approaches various men and women and presents them with the question, “can men and women just be friends?”. While many of the woman answered in the affirmative, most of the men seemed to answer in the negative, suggesting that men would generally be interested in something more; something sexual. When asked about whether their male friends were interested in having sex them, many of the women seemed to similarly acknowledge that, yes, their male friends probably were interested, so maybe there was more lurking behind that “just friendship”. In a follow-up video, the same man asked whether it would be alright for people in relationships to hang out alone with same-sex friends. While the men seemed to be of relatively one mind (no, it would not be appropriate), women, again, initially stated that opposite-sex friends are fine. However, when confronted with the possibility of their significant other hanging out alone with a member of opposite-sex, the tune seemed to change dramatically: now men and women agreed that they would, indeed, be bothered by that state of events.

“And here I thought his sudden interest in jogging was purely platonic”

So why the discrepancy in women’s responses, but not men’s? Perhaps it’s simply due to the magic of video editing, where only certain responses were kept to make a point, but, working under the assumption that’s not happening, I think there’s something interesting going on here. Understanding what that something is will require us to dig deeper into two concepts that have been floating around for some time: “the friend zone” and “Nice guys”. The friend zone, as many of you know, refers to the context where someone wants a relationship with another, but that other doesn’t return the affection. Since the interest isn’t mutual, the party interested in the relationship settles for a friendship with the target of their affections, often with the hope that someday things will change. “Nice guys” on the other hand, are typically men who are stuck in the friend zone and, upon the eventual realization that their friendship will probably not transition into a relationship, become irritated with the person they were interested in, resulting in the friendship being called off and feelings being hurt. The friendship, after all, is not what they were after; they wanted the full relationship (or at least an occasional hook up).

“Nice guys”, in other words, are only being nice because they want to get sex, so they’re not really nice, people seem to feel; hence the quotation marks. Further, “nice guys” are frequently socially maligned, seemingly because of their (actually held or assumed to be held) attitude that women are obligated to have sex or start a relationship with them because they are nice (whether any substantial number of them consciously think this is another matter entirely). Alternatively, “nice guys” are looked down on because they view the friendship – or the friend zone – as, at best, a consolation prize to what they were actually going after or, at worst, something they couldn’t care less about having. The nerve of these people; insisting that just a friendship isn’t enough! There are some very peculiar things about the label of “nice guy”, though; things that don’t quite fit at first glance. The first of these is that the earning of the “nice guy” label appears to be contingent on the target of the affections not returning them. If whomever the “nice guy” is interested in does return the affections, there is no way to tell whether he was “nice guy” or one of those actually nice guys. In other words, you could have two identical guys enacting identical sets of behavior right up to the moment of truth: if the target returns the man’s affections, he’s a nice guy; if she doesn’t and the man doesn’t find that state of affairs satisfactory, he is now a “nice guy”; not a nice guy.

That, however, is only a surface issue. The much more substantial issue is in the label itself, which would, given its namesake, seem to imply that the problem is the nice behavior of the guys, rather than the attitude of entitlement that the label is ostensibly aimed at. This is very curious. If the entitled attitude is what is supposed to be the problem of the people this term is aimed at, why would the label focus on their otherwise nice behavior; behavior that might not differ in any substantial way from the behavior of genuine nice guys? Further, why is the label male-specific (it’s “nice guys” not “nice people”, and even when it’s a woman doing it, well, she’s just being a “nice guy” too)? With these two questions in mind, we’re now prepared to begin to tackle the initial question: why do women’s response to the friendship questions, but not men’s, seem discrepant?

“Thanks for taking me shopping; I’m so lucky to have a friend like you…”

Let’s take the questions in a partially-reversed order: the first is why the term focuses on the nice behavior. The answer here is would seem to revolve around the matter of cooperation and reciprocity more generally. In the social world, when an altruistic individual provides you with a benefit at a cost to themselves, the altruist generally expects repayment at some point down the line. It’s what’s called reciprocal altruism – or, less formally, cooperation – and forms the backbone of pretty much every successful social relationship among non-kin (Trivers, 1971). However, sometimes relationships are not quite as reciprocal in nature: one individual will continuously reap the benefits of altruism without returning them in kind. Names for those types of individuals abound, though the most common are probably exploiters or cheaters. Having a reputation as a cheater is, generally speaking, bad for business when it comes to making and maintaining friendships, so it’s helpful to maintain a good reputation amongst others.

The implications for why the “nice guy” label focuses on otherwise nice behavior should be immediately apparent: if someone is behaving nicely towards you – even if that nice behavior might be unwanted – it creates the expectation of reciprocity, both among the altruist and potentially other third parties. Failing to return the favor, then, can make one look like a social cheater. This obviously puts the recipient in a bind: while they would certainly like to enjoy the benefits of the nice individual’s behavior (free meals, social support, and so on), they don’t want to have the obligation to repay it if it’s avoidable (it’s that expectation that makes people uncomfortable about accepting gifts; not because they don’t want said gifts). So how can that obligation be effectively avoided? One way seems to be to question the altruist’s motives: if the altruist was only giving to get something else (like sex), and if that something else is viewed to be of substantially more valuable than what was initially given (also like sex tends to be), one can frame the ostensible altruist as the exploiter, the cheater, or, in this case, the “nice guy”. If a woman wants to either (a) reap the benefits of nice guys, (b) avoid the costs in not reciprocating what the nice guy wants, or (c) both, then the label of “nice guy” can be quite effective. Since there behavior wasn’t actually nice, there’s no need to reciprocate it.

Bear in mind, none of this needs to be consciously entertained. In fact, in some cases it’s better to not have conscious awareness of such things. For instance, to make that reframing (nice to “nice”) more successful, the person doing the reframing has to come off as having innocent motives themselves: if the woman in question was explicit about her desire to take advantage of men’s niceness towards her with no intentions of any repayment, she’s back to being the cheater in the situation (just as the “nice guy’s” behavior is back to just being plain old nice, if a bit naive). Understanding this point helps us answer the third question: why are women’s responses to the friendship question seemingly discrepant? Conscious awareness of these kinds of mental calculations will typically do a woman no favors, as they might “leak out” into the world, so to speak. To think of it in another way, you’ll have an easier time trying to convince people that you didn’t do something wrong if you legitimately can’t access any memories of you doing something wrong (as opposed to having access to those memories and needing to suppress them). To relate this to the answers in the videos, when a woman is receiving benefits from her male friends, keeping the knowledge that her male friends are trying to get something more from her out of mind can help her defend against the criticism of being a social cheater, as well as avoid the need to pay her male friends back. On the other hand, when it’s her boyfriend who’s now being “nice” to other women, there are benefits to her being rather aware of the underlying motives.

“I swear I was just giving her my opinion about her new bra as a friend!”

Finally, we turn to the answer to second question, the answer to which ought to be obvious by now: why is the “nice guy” term male-specific? This answer has a lot to do with the simple fact that, all else being equal, women do prefer men who invest in them, both in the short and long term, but investment plays a substantially lessened role for women in drawing and maintaining male interest (Buss, 2003). Put simply, males invest because females tend to find that investment attractive. So, to sum up, women want to receive investment and males are generally willing to provide that investment. However, male investment typically comes contingent on the possibility or reality of mating, and when that possibility is withdrawn, so too does male investment wane. The term “nice guy” might serve to both avoid the costs that come with receiving that investment but not returning it, as well as a potential shaming tactic for men who withdraw their niceness when it becomes clear that niceness will not pay off as intended. Similarly, a woman might doubt her partner’s “niceness” when it’s directed towards another. This analysis, however, only examines the female-end of things; males face a related set of problems, just from a different angle. Further, the underlying male strategy is, I assure you, not any less strategic.

References: Buss, D. (2003). The evolution of desire: Strategies of human mating. Basic Books: New York

Trivers, R. (1971). The Evolution of Reciprocal Altruism The Quarterly Review of Biology, 46 (1) DOI: 10.1086/406755

5 Weak Ideas About The Origin Of Homosexuality: A Reply

Posted on January 31, 2013 by Jesse Marczyk

Back at the end of last month, Mark Van Vugt presented what he considered to be five candidate selection pressures which might explain how homosexuality as an orientation – the exlcusive preference for same-sex sexual partners – came to both (a) exist in human populations in the first place, and (b) have its existence was maintained in the face of, what appear to be, obvious reproductive disadvantages. In each of these five cases I find the arguments lacking for either theoretical or empirical reasons, and, in most cases, both. Before I get to the science, however, I would like to deal with a troubling claim that Mark makes at the beginning of his post:

“The converging findings suggest that exclusive homosexuality is not a “life style choice” but a perfectly natural sexual orientation….Although these findings make a reasonably strong claim that homosexuality is part of someone’s genotype, there is still much speculation as to how it got there.”

There are three problems I have with those two above statements (admittedly, juxtapositioned for effect) that are worth pointing out. The first is the language used: while I’m in no way about to tell you that being gay is a choice (I happen to think it isn’t one), I will point out that the opposite of “choice” is not “genetic” or “natural”. If it was discovered tomorrow that homosexuality was determined by some environmental variable, say, a specific pathogen affecting development, (Cochran, Ewald, & Cochran, 2000) that would make homosexuality no more or less of a “choice”. The second issue is that all biological traits are equally and entirely codetermined both by environmental and genetic factors. Accordingly, saying homosexuality (or any single other trait) is “part of someone’s genotype” is both trivially and true as well as potentially misleading for those who are not well-versed in genetics.

Finally, the third issue is a cautionary point I made about a year-and-a-half ago: presumably, all the talk about choice, genes, and “being natural” has little to do with statements of fact, but are rather about the moral status of homosexuality. While I fully support the moral acceptance of homosexuality, I would be very wary of basing that support on the notion that homosexuality is a “genetic” trait that people “don’t choose”. Not only do I think homosexuality should be accepted regardless of whether it’s a choice or caused by some environmental factor, but I further would hate to see the arguments for acceptance slip away on the basis of the concordance data not panning out (which we’ll see in a moment, it does not).

Politics and science make awkward bedfellows, not unlike gay men and women…

Now that the political-stuff is out of the way, we can start dealing with some of Mark’s claims. The first thing I’ll take issue with there is the prevalence data. The stable 8% figure that Mark mentions is one that exceeds most every published estimate of homosexuality I’ve seen; those have typically hovered about 1-3%. Bear in mind, one isn’t simply trying to estimate the percentage of people who have had a homosexual experience before; it’s preferences which are of primarily interest. Further, there is little reason to think that such a figure is stable, as Mark implies it is, across time, place, or history. It well might have been, but one would have an awful hard time demonstrating that it is if one wishes to go beyond pure assertion.

As for his next point, yes; there is indeed evidence that twins tend to share a sexual orientation, as they do many other things. However, the concordance rates for a homosexual orientation among identical twins (that is, given that one twin has a homosexual orientation, how often does their co-twin have a similar orientation) is only about 30%, and about 8.3% for non-identical twin pairs (Kendler et al, 2000). To make matters even more complicated, it’s worth noting that these concordance rates only tells us that some amount of what these twins share – genes, prenatal, and postnatal environments – makes it more likely that both will eventually develop a homosexual orientation, but it doesn’t tell us what that something is. Twin pairs, for instance, are similarly concordant for patterns of infectious disease (Cochran, Ewald, & Cochran, 2000), but it doesn’t mean they inherent genes that function to make them sick.

Finally, before getting to the selection pressures, it’s also worth countering the claim that homosexuality is well-documented in non-human species. Sure, there are some species that will, occasionally, engage in brief interactions more typical of mixed-sex pairs, be those interactions sexual or non-sexual in nature. What needs to be explained when it comes to homosexuality is not homosexual behaviors, but rather heterosexual avoidance. This more-or-less exclusive sexual preference for same-sex conspecifics has only been documented in rams, to my knowledge, and in no other non-human species, much less many or most of them.

Selection Pressures: Kin Selection
The first of the five selection pressures that Mark mentions is kin selection: helping others who share your genes reproduce. As Mark correctly points out, there’s little evidence for his hypothesis being correct, but the issues are much larger than that. For starters, the relationship coefficients don’t work well here: for each offspring a homosexual individual doesn’t produce, they would need to ensure that a full sibling produced an additional two that they otherwise wouldn’t have had for them to just break even and for this hypothesis to work. This would require an intense level investment that, if it existed, would be plainly obvious to any observer. It’s not enough that a homosexual individual is occasionally or even often nice to their relatives; they would need to be utterly devoted around the clock.

More to the point, though, is the seemingly apparent point that having a same-sex sexual attraction does nothing to help you invest in kin. Sure, maybe an asexual preference would work, if you wanted to save the time otherwise spent pursuing sex; a facultative heterosexual preference would probably do just as well, if not better. A homosexual orientation, on the other hand, is a complete waste of time; it would be a pointless distraction from the investment issue. Unless seeking out same-sex sexual relations was somehow functional in terms of increasing investment (or a rather odd byproduct), this explanation makes little sense.

Ants are very helpful, yet not very gay…

Selection Pressures: Group Selection
Group selection – the idea that a trait can spread if it offers group-wide advantages despite being individually detrimental – is a conceptual nonstarter, running counter to everything we know about how evolution works. Since I’ve written about this matter before on several occasions, there’s little need to continue beating this theoretical horse which has been dead since the 1960s. As Mark, again, points out, he knows of no evidence in favor of this hypothesis either, so there’s little less to say about it, other than that it doesn’t sound like a very “big” idea.

Selection Pressures: Sexual Attraction
This one, I admit, is probably the strangest of the selection pressures Mark posits. The idea here seems to be that because women might find homosexual men sexually attractive, this could give homosexual men a reproductive advantage. Now, perhaps I’m misunderstanding the basic idea in some fundamental way, but if an individual with a homosexual preference is found to be attractive by opposite sex individuals, it would seem to not matter much, as it’s quite unlikely that the two will ever end up having sex at all, let alone frequently. Provided these increased opportunities for sexual encounters even exist(Mark says there’s no evidence available that they do), they wouldn’t seem to do much good if the urge to take them is all but absent.

In case the problems aren’t plainly apparent at this point, imagine a hypothetical species of bird, like a peacock. In this species, males grow elaborate ornaments that females find to be attractive, generally speaking. Growing these ornaments, however, carries a cost: it makes the males sterile. In this case, no matter how attractive a male is to the females, his genes will never be benefited because of it. Attractiveness only matters so much as it leads to reproduction. No reproduction, no selection.

Selection Pressures: Balanced Selection
This argument at least poits that homosexuality is reproductively detrimental. These detriments are made up elsewhere, though, in the form of benefits to other carries of the genes. In essence, this argument says homosexuality is a lot like sickle-cell: harmful in some cases, but beneficial in others. There’s nothing theoreticall wrong with this possibility, but there are some serious practical hurdles. Specifically, if homosexual orientations ensured that 1-8% of the population was, effectively, sterile, there would need to be tremendous compensating benefits. Sickle-cell, for instance, is only common in areas that have a ton of malaria – which can kill huge minorities of populations and leave even more severely harmed – and pretty much the only known byproduct of its kind with a fitness hit as great as homosexuality (Cochran, Ewald, & Cochran, 2000). It also doesn’t fit well with the concordance rate data. So, while this explanation is theoretically possible, it’s highly improbable. At the risk of sounding like a broken record, there’s also no known evidence for this being the case.

Selection Pressures: Sexually Antagonistic Selection
This brings us to the final selection pressure. Here, the idea is that a gene is detrimental when it’s inherited by one sex, but beneficial in the other. This is another theoretically plausible suggestions with some consistent evidence behind it (but the account isn’t anywhere near complete, and only considers male homosexuality). Unfortunately for this suggestion, like the above hypothesis, it also suffers from the concordance rate data. It would also require that females consistently more than make up for the detriment to the male offspring, reproductively. Remember, this isn’t just a matter of slight disadvantages; this is a matter of effective sterility. Further, such sexually antagonistic issues tend to be weeded out over time, as any new modifications that can avoid the costs associated with expression in males will be selected for. Even if this was a viable account, then, it would still be far from a complete one, as it would not be able to explain why some of the twin pairs turn out concordant, but most don’t, why these reproductive costs have yet to be eliminated, and it’s missing an account of female homosexuality.

“Would you care for a sixth cup of weak tea?”

Out of the five “big” ideas, then, four seem to be basically dead in the water and the fifth, while potentially plausible, is by no means conclusive or complete. In my experience, poor outcomes like these can be seen frequently when people attempt to use scientific research to justify some political or moral opinion: any available evidence that can be potentially interpreted in a favorable light is seized upon, no matter how weak or nonsensical the underlying connection between the two is. The goal, after all, doesn’t appear to be accuracy, but rather persuasion; to the extent that the former helps with the latter, all the better for the persuader, but their need not be any necessary connection between the two goals.

References: Cochran, G., Ewald, P., & Cochran, K. (2000). Infectious Causation of Disease: An Evolutionary Perspective. Perspectives in Biology and Medicine, 43 (3), 406-448 DOI: 10.1353/pbm.2000.0016

Iemmola F. & Ciana, A. (2009). New evidence of genetic factors influencing sexual orientation in men: Female fecundity increases in the maternal line. Archives of Sexual Behavior, 38, 393-399.

Kendler, K.S., Thornton, L.M., Gilman, S.E., & Kessler, R.C. (2000). Sexual orientation in a U.S. national sample of twins and nontwin sibling pairs. American Journal of Psychiatry, 157, 1843-1846

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