Thanks everyone for the interest and your patience – a family emergency arose yesterday so I’ve been unable to respond until now.
I’ll try to address some of the issues that were raised. Thanks to Guppy and Don (runtime) and other who have made similar points.
Here goes:
Some people expressed deep skepticism of using evolutionary theory to understand human behavior. I obviously disagree, but I don’t think I can convince true skeptics, especially in a post like this. So I’ll mostly leave it alone. For those who are truly interested in understanding evolutionary approaches to human behavior and why the oft-repeated critiques are generally incorrect, I’d be glad to provide reading suggestions, but this is a good place to start:
http://www.psych.ucsb.edu/research/cep/primer.html
Some wondered why any evolutionary or biological explanation is necessary to explain the patterns. In other words, couldn’t various socialization forces alone account for everything we found in this and previous studies? Logically, yes they could. In fact, almost any well-developed theory (or ideology) will be sufficiently flexible to “account” for anything. But the key to good science is developing and testing falsifiable predictions. So imagine I had discussed this issue with people around 1980. I would explain that males participate in distance running 4x more than females and that there are 6x more males running relatively fast. Then I asked people to imagine that the participation differences and financial incentives favoring males would completely disappear by the late 1990s. Would the socialization hypothesis and its proponents predict that the number of relatively fast performers would disappear or at least become very small by 2011? It certainly would. Now some might object that “testing this prediction” in this way isn’t fair since I don’t have anyone on the record saying precisely this. But this isn’t a good objection because there are many scholars who have said this about sports in general in the U.S., i.e. the sex differences in sports interest and motivation have disappeared or soon will. (Btw there isn’t much (any?) data suggesting this is true.) So, for anyone who is keeping score fairly, the distance running results that we have documented over the past 30 years must count against a pure socialization hypothesis.
But some have argued that eliminating sex differences in participation opportunities and incentives isn’t nearly enough. In other words, we need to eliminate all kinds of socialization differences for boys and girls, and we have a very long way to go on this. I have three responses. First, this may be true but this is contrary to what the Supreme Court believes which holds that making changes in school sports via Title IX will be sufficient. Second, this may be true, but it doesn’t contradict an evolutionary account which holds that socialization practices will often (but not always) complement biological mechanisms. (If you find it surprising that an evolutionary approach to understanding behavior hold that environmental factors are important, then you aren’t up to speed on evolutionary psychology or evolutionary biology.) Third, there is apparently very little strong evidence that socialization contributes to sex differences in sports interest and motivation. Many scholars in sports science would be scandalized that I say this because they believe it so strongly. But most (all?) of their evidence is easily open to other interpretations. For instance, showing that children, especially boys, who say they like sports more also are much more likely to be signed up to play organized sports is consistent with a socialization hypothesis. However, it’s also consistent with a simpler account that parents respond to their children’s inborn interests. My students and I are still reviewing the relevant evidence on this so I’m not entirely confident about it yet. And again, I’m not saying that socialization doesn’t matter, only that there is apparently very little strong empirical evidence that it does. In his book, The Blank Slate, Steven Pinker has made very similar points about developmental psychology in general. We (most scientists and the public) believe our socializaion hypothesis so strongly that we haven't bothered to test it against alternatives.
So what do we know contributes to sex differences in sports interest? Sports interest seems to be part of a general package of boy-typical behavior. And we know that much of this is caused by processes that occur prior to birth, especially the effects of androgens on the brain. For instance, dozens of studies have shown that girls with the disease congenital adrenal hyperplasia (CAH) are exposed to abnormally high levels and their interests and behavioral styles are much more boy typical than control girls. Three studies have shown that CAH girls have unusually high levels of sports interests, especially for masculine sports. There are many other lines of evidence for the importance of prenatal hormones, including David Reimer and more than a dozen similar cases. Sheri Berenbaum and Adrian Belz have recently published a review of all the relevant kinds of evidence, and I’d be happy to email it to anyone who needs access. By the way, if you doubt this prenatal androgen research because someone told you it was unconvincing, then your source probably hasn’t consulted the empirical evidence in the past 10 or 15 years. Again, I'm not saying that all sex differences are caused by prenatal hormones, only that it is definitely known to contribute. Other things must matter too.
Asfadsfsda suggests that more males have the underlying biology (skeletal features, aerobic capacity) necessary to be good runners. This is a viable and important hypothesis. I hope that someone will gather data to test it. Part of the reason I am trying to publicize these results is to stimulate a research group to gather some relevant skeletal data (I do know the relevant aerobic data pretty well, though, and it doesn’t support this hypothesis.) I’m not testing this hypothesis myself because no matter what I do, nobody will find it convincing. For instance, imagine I hypothesize, based on relevant literature, that narrow hips are necessary for excellent running. Then if I find that similar numbers of men and women in the population have this trait, people will dismiss this finding and say that hip width wasn’t the crucial trait; it was something else I haven’t looked at. It might even be difficult to publish this “negative” result.
That’s all I’ve got time for now. Thanks again for your interest and thoughts.
Let’s keep it civil.
Rob Deaner