✹ About Wednesday 11 May 1664 Nate Lockwood on 14 May 2017 • Link Robert, sorry about the tech talk. 1. The ratio of weight of testicles to body weight is correlated 'promiscuity' for most animals, that is, a very low ratio correlates with monogamy and a high ratio with promiscuity such as a bull or a ram. The ratio for humans fall in the low end, nearly or somewhat monogamous. 2. Sexual dimorphism is the difference in appearance of males and females of animals. Some birds mate for life (or at least the breeding season), that is, they are monogamous. They are the same size and color and it's difficult or impossible to tell the males from the females without an examination. Evolutionary pressures are pretty much the same for both sexes. We can tell males from females for most animals as they males tend to be larger than the females and may be colored differently, common in birds, or have other characteristics such as antlers, manes, etc. These are used to intimidate rival males and to attract females. Sexual dimorphism is correlated with promiscuity. The average height and weight of men is greater than the average woman, men, on the average are more muscular and have beards. This indicates that we are not monogamous - on the average but are on the low end of the promiscuity scale. 3. The 'head' of the human penis is shaped in such a way as it can 'scrape' out semen in a woman's vagina. This is not necessary with monogamy so it implies promiscuity. When I first heard about the study that Paul Dyson referenced I thought the promiscuity kind of high. The more recent study I thought a bit low but it was regional and not world wide and those studies are hard to do. If I can find the reference I'll post it here. In the last year a new article said that a species of bird in the British Isles in two or three hundred years of birdwatching had never been seen to 'cheat' but males and females could be easily distinguished. Then some watchers got their hands on night vision goggles. In the dark the males would scoot off and mate with females whose mates were doing the same thing!