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Behavior
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Monogamy & Mating Habits
What does human anatomy and evolution reveal about the history of human mating habits?
Birth of Patriarchy
The roots and purpose of humanity's oldest institution of oppression
Sacred Animals
Four creatures used as symbols across cultures since the dawn of history
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Civilization
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Global Trade Network
Clues revealing trade and cultural exchanges spanning the globe before the invention of agriculture
Lost Lands
Historic accounts of cultures thriving on lands submerged after the end of the ice age
Florida Pyramids
Rumors of mysterious pyramids hidden in the Everglades
North American Megaliths
Unexplained structures found along the eastern coast of the US
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Human Anatomy and Sexual Behavior
Rape is a common occurence within modern human cultures, and while female humans have advocated against it and it is acknowledged as an unwanted form of violence, many argue that rape is simply part of our nature. But is there evidence for this?
Clues of our behavioral origins lie within our anatomy. We've observed consistent patterns in primates and learned how certain physical traits are adaptive to specific sexual strategies. Sexual dimorphism, testicle and penis size, the presence or absence of a penis bone, female sex drive, and unique evolution of cryptic ovulation by human females are all clues to be explored.
There is a high correlation between body size and tendency towards monogamy, and evolutionary reason for it. The motivation for virtually all violence by males against females within a primate species is mating access. Those that engage in sperm competition or hoard females in harems have very violent social lives - the more successful a male is in fighting off other males and physically bullying females, the more likely he is to mate and pass on genes. Here, size matters. Monogamous species, on the othe other hand, tend more to be peaceful and egalitarian. Species that mate for life have little diffence in body size, species that engage in sperm competition see larger size discrepencies, and species where males keep harems of females have the biggest ratio. Monogamous species most often have a 1:1 size ratio. Humans have a 1.1:1 size ratio. Larger than 1, but still smaller than that of chimps (1.2:1) where sexual coercion of females is normal.
Large testicle-to-body-size ratio is an important adaptation for males who engage in sperm comptetition. The larger the ratio, the more often the males of that species mate in a day. In chimp society, both males and females are highly promiscuous and females will be inseminated by multiple males in a day when they are ovulating. In monogamous species, male access to a female is guaranteed, so the need for constant insemination in order to increase chances of siring offspring is not necessary (in fact, mating is a primarily a way for reinforcing bonds between mates and plays no part in social competition or hierarchy.) Human males have the smallest testicle-to-body ratio of all primates, suggesting not only a lack of sperm competition, but that our species evolved to have the lowest ejaculation rates of all primates.
The human penis is unique among all primate phalli. Unlike human testicles, males have the largest penis-to-body size ratio of all primates. Our species also evolved away the penis bone - a feature particularly useful in sperm competition and forced insemination. Small penises are also far more useful for forced insemination. So what possible use would a large, not overly-forceful penis be to early hominids? If it wasn't useful for the male to spread his sperm by choice, then was it due to female selection?
Human females enjoy and seek out sexual encounters. While this isn't unique to human females, it is not true of all primates - many must simply tolerate their males. There are even early human artifacts that appear to be sex toys. They also maintain their sex drives outside of periods of ovulation. Not being subject to irresistable physical coercion, coupled with their own drive for orgasms, likely would have resulted in high sexual peformance expectations by females, or would have resulted in them taking partial or full control of sexual encounters in order to ensure their own enjoyment.
Female humans have their own anatomical peculiarities among primates which act specifically to cloak their fertility status, which other primates advertise regardless of mating strategy and female sexual satisfaction. Other primates (and the vast majority of female mammals) experience estrus - a time of high sex drive and physiological changes that make it obvious they are fertile to males.
Another unique physical characterestic not shared by any other species is that female humans have permanently enlarged breasts as adults. For mammals, mammaries become engorged when ducts fill with milk after mating. During this time, females are not fertile and not receptive to mating. This feature, along with the lack of estrus, means human females evolved away any indicators of fertility or lackthereof.
It seems sensible that humans want to exercise high control over birthing. Pregnancy is especially dangerous for humans. The extra-large cranial size of infants created a high chance of death for mothers, as well as an extremely high calorie demand. Breastfeeding also would have been especially taxing as human breastmilk is so high fat. Juvenile humans also have especially long childhoods and are born especially helpless, and thus require a higher proportion of attention and resources than other primates. High birth rates would not have been desirable.
Male humans were less able to physically coerce females, less able to rape them, and had lower sex drives than other primates. They lacked the physical necessities to compete with other males sexually. They had no physical triggers advertised to them by females, and with potentially sexually aggressive females who had their own motives for seeking out sex likely would not have needed them. Surely, they would have been some of the most docile and least aggressive of all primate males. Our species shares many characteristics of monogamous species as well as some that are entirely unique to our species, hinting our mating strategy may also have been unconventional. Whatever the case, the modern norms of promiscuity, sexual violence, and sexual incompetence were unlikely to have been the norm for our ancestors.
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