The human penis is longer and thicker than that of other great apes. Even the largest gorillas, which are twice as heavy as a human, have an erect penis of only a little over six centimeters.
But our testicles are quite small. In chimpanzees, their weight is more than a third of the brain, and we have less than three percent. The size of the human penis and testicles is dictated by our mating strategy, which allows us to better understand the origins of early human culture.
Primates have very varied mating behavior. It can be monogamous, polygynous (this is when the male has several females), and also mixed, when there are several males and females in the group. One indicator of mating behavior in a species is the difference in size between males and females. The more pronounced this sexual dimorphism, the higher the likelihood of polygynous and mixed group relationships between males and females. This can be seen by observing our closest relatives, which are chimpanzees and gorillas.
Male chimpanzees are much larger than females and have a mixed mating system. In fact, male chimpanzees have sex all the time with any female and under any pretext. Therefore, the female can simultaneously have sperm from different partners. Consequently, direct competition is between spermatozoa, and not between the animals producing them. For this reason, chimpanzees evolved into huge testes that produce large amounts of sperm, several times a day.
Male gorillas are also much larger than females, but they have a polygynous or harem mating system, where several females live with one male. Since the gorilla has no competition inside the womb, males do not need to compete in testicular size to produce more and more sperm. Therefore, their testicles are rather small. The same applies to modern humans, whose testicles are also quite modest in size and produce a small amount of sperm. In fact, a person's sperm count is reduced by over 80 percent if they vomit more than twice a day.
Compared to our closest relatives such as chimpanzees, gorillas, and orangutans, humans have a large penis. However, primate expert Alan Dixson, in his beautifully written book Primate Sexuality, puts forward the idea that looking at all primates, including the lesser apes, is wishful thinking.
Comparative measurements indicate that the human penis is exceptionally long. For example, a native of East Africa, hamadryas, has an erection length of 13 centimeters, that is, slightly shorter than that of the average man, although his weight is three times less.
Besides, the human penis is very simple. It does not have bumps, protrusions, bulges and other interesting features that other primates can boast of. Simple penises in primates are usually where their species are monogamous.
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The mystery of monogamy
This observation contradicts the fact that men are significantly larger than women. This circumstance indicates that in the process of evolution, humans more often had polygynous than monogamous marital relationships. This is confirmed by anthropological data showing that modern humanity for the most part enters into polygynous relationships. Anthropologists Clellan Ford and Frank Beach, in their book Patterns of Sexual Behavior, point out that 84% of the 185 human cultures for which they have data have or polygamy existed.
But even in these societies, most people remain monogamous. Polygamy is usually the privilege of wealthy men with high social standing. It is worth noting that hunter-gatherers around the world have maintained only permanent or long-term monogamous relationships. This suggests that our ancestors had just such a mating system.
But at first glance, it might seem that it is wiser for men to have sex in order to produce offspring with as many women as possible. Human monogamy has long baffled anthropologists, and they have worked hard to understand what causes a man to stick to one woman.
There are three main theories. First, children need parental care and education for a long time, since they grow up slowly with us. Secondly, the male must guard his female from other males. Thirdly, our children are absolutely defenseless for a long time, and other males can kill them. Therefore, in order for the children to reach maturity, the male must stay with them and protect them, both physically and socially. This is probably why males are larger than females.
Looking at the evolution of the human monogamous mating system through the lens of human society, it becomes clear that it takes enormous social effort to protect multiple females. A man can protect his many women only when he receives additional resources and power. He usually makes it so that they are protected by other men. Therefore, monogamy can be called a means of adaptation to protect the female and children from other males. If there are several partners, it becomes much more difficult to do this. So monogamy is socially based and reinforced by cultural norms.
Therefore, in a complex human society, the largest and most important sexual organ is the brain. Somewhere in the evolutionary past, our minds and our social behavior became the primary means of accessing sex partners. And the size and outlandish shape of the penis has nothing to do with it.
Mark Maslin