Analysis of information sources in references of the Wikipedia article "انتخاب جنسی در انسان" in Persian language version.
The races of man differ from each other, and from their nearest allies, in certain characters which are of no service to them in their daily habits of life, and which it is extremely probable would have been modified through sexual selection
It is not implausible that, with natural selection refining their diagnostic skills, females could glean all sorts of clues about a male's health, and the robustness of his ability to cope with stress, from the tone and bearing of his penis.