This post is part 3 in a series of posts about gender In my first post I proposed 5 scientific and reason-based tests to validate or falsify the theory that gender is not innate. I covered 2 tests in the last post and I will cover the remaining tests in this post. I am using evidence gathered by Harvard Professor and New York Times Bestselling author Steven Pinker. The evidences can be found on page 346-347 of his pulitzer finalist book, The Blank Slate: The Modern Denial of Human Nature.
If parents treated boys and girls differently, then that would count as evidence against (Y). If parents treated girls and boys the same, then that would count as evidence against (X).
Contrary to popular belief, parents in contemporary America do not treat their sons and daughters very differently. A recent assessment of 172 studies involving 28,000 children found that boys and girls are given similar amounts of encouragement, warmth, nurturance, restrictiveness, discipline, and clarity of communication. The only substantial difference was that about two-thirds of the boys were discouraged from playing with dolls, especially by their fathers, out of a fear that they would become gay. (Boys who prefer girls’ toys often do turn out gay, but forbidding them the toys does not change the outcome.) Nor do differences between boys and girls depend on their observing masculine behaviour in their fathers and feminine behavior in their mothers. When Hunter has two mommies, he acts just as much like a boy as if he had a mommy and a daddy.
If animals that were genetically close to humans like mammals and especially primates randomly assigned gender roles then that would be evidence against (Y). If the gender roles within the animal kingdom were similar to humans, then that would count as evidence against (X).
Many of the sex differences are found widely in other primates, indeed, throughout the mammalian class. The males tend to compete more aggressively and to be more polygamous; the females tend to invest more in parenting. In many mammals a greater territorial range is accompanied by an enhanced ability to navigate using the geometry of the spatial layout (as opposed to remembering individual landmarks). More often it is the male who has the greater range, and that is true of human hunter-gatherers. Men's advantage in using mental maps and performing 3-D mental rotation may not be a coincidence.
Behavior is affected by certain states of the brain. This has been shown in many psychological and neurological studies. If boys and girls had exactly the same brain characteristics, then (Y) would be false. If they had significantly different brain characteristics then (X) would be false.
The brains of men differ visibly from the brains of women in several ways. Men have larger brains with more neurons (even correcting for body size), though women have a higher percentage of gray matter. (Since men and women are equally intelligent overall, the significance of these differences is unknown.) The interstitial nuclei in the anterior hypothalamus, and a nucleus of the stria terminalis, also in the hypothalamus, are larger in men; they have been implicated in sexual behavior and aggression. Portions of the cerebral commissures, which link the left and right hemispheres, appear to be larger in women, and their brains may function in a less lopsided manner than men's. Learning and socialization can affect the microstructure and functioning of the human brain, of course, but probably not the size of its visible anatomical structures.
These are a few of the many well documented and scientifically tested evidences that disprove the theory that boys and girls are identical at birth except for genitalia.