The planet’s first act of intercourse took place 385 million years ago. It wasn’t a gentle affair, with male fossils of the placoderm Microbrachius dicki developing bony L-shaped genital limbs to transfer sperm to females.
Kinsey became a household name when his book came out in 1948, reporting that 85 percent of men had premarital sex and that 10 percent were gay. His work would eventually lead to states undoing laws against fornication and adultery.
Humans
Sexual activity has been a part of human life since prehistoric times. However, understanding and expressing sexuality has varied significantly among different cultures and time periods. In ancient civilizations, sex was often intertwined with religion, mythology and power dynamics. In some cases, sex was even taboo.
One of the first major anthropological contributions to the study of sexuality was made by Swiss jurist Johann Bachofen. His 1861 book Mother Right: An Investigation of the Religious and Juridical Character of Matriarchy in the Ancient World was an important influence on many thinkers to come. While based on a close reading of ancient mythology, Bachofen’s ideas were controversial. He claimed that human sexuality in the beginning was chaotic and promiscuous.
In contrast, he later advocated that social mores should be brought more in line with actual behavior. He argued that masturbation and oral sex within marriage were natural, but he also promoted tolerance of everything from homosexuality to pedophilia.
As early humans evolved, they became more sophisticated, and their sexual behavior developed as well. Scientists have found that the earliest vertebrate ancestors of humans used a similar method of reproduction as we do today. They were called placoderms, and male fossils such as Microbrachius dicki developed bony L-shaped genital limbs known as claspers to transfer sperm to females. Females, for their part, had small paired bones to lock the male organs in place during mating.
Neanderthals
The term “Neanderthal” conjures up a picture of primitive ’cavemen’. But despite this, fossil and genetic evidence shows that these stocky hominids were intelligent, accomplished people. Moreover, their brains were bigger than ours on average and they were adept at making tools. Several Neanderthal skulls have been excavated, including one from Gibraltar which dates back to nearly five years of age.
It’s also possible that a small percentage of modern humans interbred with Neanderthals. A study published in 2010 revealed that 1 to 4 percent of some modern human genes came from these stocky ancestors. This suggests that we might have picked up genes, and perhaps even some immunity boosts, from them before they went extinct.
Neanderthals had a similar build to ours, so it’s not hard to imagine them as sexually active. But despite this, they were not promiscuous by any means. Scientists can estimate their propensity for sex by studying the differences between the lengths of their index and ring finger. Chimpanzees and gorillas have a lower digit ratio than humans, while early modern humans and the Neanderthals had higher ones.
Moreover, research into the shape of their bones shows that women’s bodies were less muscular than men’s. This is likely because they did not need to exert themselves as much in the hunting and gathering process, unlike males who needed strong muscles for climbing or escaping predators. This is supported by a study of the limb bones of Neanderthals that found that, while their thighs were quite muscular, their lower arms were weaker.
Homo erectus
Homo erectus is the first human ancestor that can be traced back in the fossil record. Its larger brain and more advanced teeth enabled it to hunt and gather for food. This diet likely consisted of a variety of foods, including meat and tubers. Animal remains with cut marks indicate that the early humans were able to butcher animals to get at their meat and marrow.
The earliest Homo specimens were discovered in Africa and Asia. The first was a skull cap, called Pithecanthropus erectus by Eugene Dubois, found along the Trinil River in Java in 1894. The femur that was found with the skull cap is a clear indication that this was a large-bodied, upright hominin.
It is also the first Homo specimen to show evidence of encephalization, which is the increase in brain size relative to body size. This is an evolutionary trait that has only been seen in humans and a few other mammals. Scientists are unsure why this happened, but it is likely that the pressure to adapt to an ever-changing environment or the opportunity to hunt and gather increased the selection for more complex behavioral characteristics that are associated with larger brains.
The discovery of a complete skeleton, known as Turkana Boy, in the late 1990s was a turning point in the study of early humans. The skeleton was the oldest that showed a clear upright posture and a remarkably human-like face. It was also the earliest to demonstrate a variety of other features, such as dexterous hands that allowed the use of stone tools.
Homo sapiens
Holly Dunsworth is a professor of anthropology at the University of Rhode Island. She specializes in the fossil record and living primates, especially humans. She also studies sexual reproduction and its evolution in pre-humans. She believes that all mammals have some kind of innate sense of sex. However, she admits that there is no proof of early sex among humans.
Homo sapiens evolved in Africa and populated the world, co-existing with Neanderthals in Europe, Denisovans in Asia, and the now extinct Homo floresiensis in Indonesia. But today only modern humans survive. The Jebel Irhoud fossils have no features that define our species. This suggests that the skulls belonged to a transitional population that split off from archaic Homo sapiens, possibly along with the Laetoli cranium and LH 18 from Florisbad, Omo 1 and 2 from Ethiopia, and Skhul 5 from Israel.
The genetic analysis of the mtDNA from these fossils suggests that they interbred with modern humans. In fact, the Jebel Irhoud remains are a mix of different human lineages, including some from Africa, Europe, and Asia. The fossils are believed to be around 200,000 years old. Modern humans evolved from the archaic Homo heidelbergensis, and they co-existed for a time with Neanderthals and Denisovans before becoming the only survivors. Neanderthal genes remain in 3 to 4 percent of modern-day Europeans and Asians, while the Denisovans went extinct.
