To claim that there are no evolutionary differences in behavior and psychology between men and women is fatuous. The data show otherwise, though of course for most traits we don’t know if it’s genetic. But the default hypothesis, based on observation of other species (especially primates) is that at least some psychological and behavioral differences will be based on genes that evolved via selection in our ancestors. Why is the brain immune to evolved, sex-specific differences but the body is not?Holly Dunsworth at U. Rhode Island posted a series of claims on Twitter about human sexual dimorphism, and was picked up in a New York article, wrapping up with these tweets:
Knowledgeable people aren't objecting to facts. They're objecting to biased story-telling and its annoying and harmful consequences.— Holly Dunsworth (@HollyDunsworth) December 16, 2016
Not only is [female procreation during childhood growth] absent, but selection on women's bodies be the driving force (if such a thing could be identified) ...— Holly Dunsworth (@HollyDunsworth) December 16, 2016
...and it's as if women don't exist at all in these tales except as objects for males to fight over or to fuck but it's nice to have choice!— Holly Dunsworth (@HollyDunsworth) December 16, 2016
There's a lot of things one could say about this, but what's most preposterous about it is the idea that science is somehow responsible for being thoughtful or kind — i.e., adhering to "safety", the prevailing groupthink, a problem the atheists ran into a while back. Coyne answered these silly remarks resoundingly well here, and at even greater length, here. He makes four points, three of which are strongly supported by data:
As long as evolution, especially human evolution, is publicly championed like that, it's not going to catch on among thoughtful kind people.— Holly Dunsworth (@HollyDunsworth) December 16, 2016
Moreover, regarding Dunsworth's remarks, female growth emphatically does not stop after menarche (females continue to grow even into their late teens). "Dunsworth’s hypothesis is not only unsupported by data, but fails to explain the growth data that do exist." He concludes:
- Among species of primates, there’s a good correlation between the polygyny of a species and sexual dimorphism: those species in which males have a higher variance in offspring number, and in which males thus compete more intensely for females, also show a greater ratio of male/female body size, even when corrected for phylogeny. (Too, in primate species in which males fight each other over females, the relative size of the canine teeth, used in battle, is larger than in species showing less direct male-male competition.)
- In humans, as in many other species in which males compete for females, the sex ratio at birth favors males. They then die off at a higher rate due to higher risk-taking and exploratory behavior, and also senesce faster, which is why among older humans there are so many more females than males. (Check out any Gray Line tourbus.) This is predicted by sexual selction theory.
- In line with the above, in humans and other primates, males show from the outset great exploratory and risk-taking behaviors, and as adults show many other behaviors that differ from those of females, such as greater dispersal. Is this due to the Primate Patriarchy? Probably not, given that these differences in behavior are shown in many species besides ours and make evolutionary sense.
I can’t believe that simply my writing a post on human sexual dimorphism and its implications would drive anybody away from studying human evolution. After all, the give-and-take of hypotheses, critical thinking, and data are the very meat of science, and if you disagree with somebody, you don’t simply walk away from a field. I sure as hell am not leaving evolutionary biology because Dunsworth and New York Magazine took out after me!This is a great response, and I'm glad to see someone pick up this flag.