History of Sex Part 2: The Evolution of Genitalia & Sex


The evolution of human sex and anatomy is vast and a lot kinkier than you probably think. In fact, you may find our ancient past arousing, self validating, and at the very least – surprising.

For the last 100,000 years (give or take) we’ve been anatomically the same. Experts feel that, if so, then our cave-dwelling ancestors had to have enjoyed sex too, right?


Anthropologists Gregory Cochran and Henry Harpending illustrate in their book, The 10,000 Year Explosion, that we are capable of extremely rapid evolution, “the human body has built resistance to malaria, blue eye color, and lactose towards evolutionary growth.” It’s all about that natural selection and branching evolutionary changes.


So, what does this mean for our penis parts, vulva bits, and nips? Why do they look the way they do, and why have they changed so little?

Growers, Not Showers

When compared to our most closely related primates, testicular size has changed. Not to mention bigger, thicker penises. In Sex At Dawn: The Prehistoric Origins of Modern Sexuality, the authors reveal that, “testicular tissue in humans, chimps and bonobos (but, interestingly, not gorillas) is controlled by DNA that responds unusually rapidly to environmental changes.” 

The writers, anthropologists Christopher Ryan and Cacilda Jetha, speculate that the evolutionary adaptation to having larger genitalia than our genetically similar primates was due to prehistoric mating rituals. Sex did not adhere to monogamy. In fact, it was common for any given human to possess multiple partners at any given time in their adult life.  

Cervical Combat

Similarly, the human cervix evolved to accommodate a promiscuous lifestyle in order to promote competition between sperm. You know, a sperm battle, of sorts. Think about it like this: on average, 14 million sperm are released at ejaculation, but only one (if any) is permitted to fertilize the egg. On top of that, sperm is treated as a foreign invader in the female body, being rejected or chemically absorbed. Just to give you a visual for what that looks like, there are 100 antigens to every single sperm cell ready to combat the body’s “invader.” Talk about a hostile environment.

Beautifully Breasted

Female breasts are pendulous bags of fat, really. Yes, they’re used for breastfeeding, but we don’t need all that extra flesh. So, what purpose does it serve? Breast evolution is thought to arise from ovulation signals and signs of fertility. Ryan and Jetha speculate in their book that breasts then adapted for pleasure senses for the male and female. During ancient times in some cultures, voluptuous women were seen as being more fertile and able bodied for childbearing.

Nina Paley

So while all breasts are great, no matter what their size, never tell a breast loving human that boobs serve no darwinian purpose.


While anatomy has been pretty static as the millennia have gone on, the way we feel about sex tells a different story… Or does it?

Sex Sounds & Orgasms

“Female copulatory vocalization” (the noises females make during sex and orgasm) is believed to promote sperm competition (just like the cervix), ejaculation, and the promiscuous sexual mating theory. 

Ryan and Jetha explain that it’s perceived in the scientific community that male orgasm and ejaculation is so short – and usually easier to come by – due to threats from predators. On the other hand, the female orgasm is typically more drawn out due to its function of increasing chances of fertilization with the male that can please her. If you think about it, all that sexual noise making isn’t selectively fit to exist! Think A vocal female or even male orgasm is the opposite of camouflage! Something would have statistically eaten us… in a not so pleasurable way.

Vocality in sexual delights and our capacity for multiple orgasms all support that our ancestors were sexually wild beings – and they enjoyed it.

Not Built for Monogamy

Ryan and Jetha hold that for the past few million years, human beings and our ancestors have mostly functioned in small intimate bands in which most adults possessed several sexual relationships scattered over any given time. There’s scientific evidence from many anthropologists that our ancestors use to engage in orgiastic rituals, unhesitant partner sharing, and an open sexuality undaunted by guilt or shame. Our closest genetic relatives, bonobos and primates also engage in the same behavior. Female chimps have sex several times a day with willing mates. Bonobos have group sex that is calming for those involved and even aids social networks.

However, about 10,000 years ago, the rise of agriculture and private property halted the norm of this approach to sexuality for humans. 

Still Naughty Behind Closed Doors

As time passed and various religions and cultures culminated, sex and pleasure would be practiced and viewed very differently across time and place. And, in a contradicting way at that.

Victorian men would honor and respect the females in their lives, but while using the art of prostitution to purge them of their wildest desires. Disease, misery, smells and itches pre Industrial Revolution would complicate sexual pleasures for people of its time. The liberalization of sexuality would boom big time in the 1960s and even more still with the introduction of the birth control pill; fighting the good fight against society’s views.


Since then, openly seeking out sex for pleasure rather than procreation has continued unabated – and most likely for the days to come. 

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