Otherwise they seem expensive. Sexually immature, prepubescent boys enjoy a range of sexual response similar to that of adult women. This capacity definitely exceeds in the ability of teen-age boys who, in turn, are much more capable than older males. When the females were promiscous, the sperm of each male would have to compete with those of other males, and the male producing the most sperm was most likely to generate offspring. Women were proportionate to men, with Orientals having smaller vaginas and blacks larger ones, relative to Caucasians.
Recent data show similar patterns.
Several subsequent studies are confirmatory. Testing an evolutionary hypothesis.