Don’t look now, but the history of homo sapiens — and of human-like creatures on planet Earth — is getting progressively weirder and more titillating.
Scientists conducting studies of human genes are learning lots of interesting information about the development of our species. One of the more provocative findings is that our genetic information indicates that there were multiple instances of significant homo sapien interbreeding with other human-like species — specifically, the Neanderthals, and a mysterious, largely unknown species called the Denisovans — that left indelible marks in the DNA of modern humans. And it also appears that the cross-breeding provided us with some useful genetic material, including genes that enhanced the operation of the human immune system and helped our ancestors fight off pathogens.
Not much is known about human history before the dawn of civilization. Most of what we understand comes from looking at fossils of human ancestors and attempting to piece together the gnarled branches of the human family tree. Human genetic analysis provides a different kind of window to the past of our species. It’s now obvious that the early days of the human species saw our ancestors competing with — and apparently having lots of sex with — other hominid species. We couldn’t have been too much different from them, because the genome evidence means that when humans had sex with Neanderthals and those enigmatic Denisovans, their one-night stands produced pregnancies and non-sterile offspring that, in turn, shared their genes through mating. All of that cross-breeding among different species helped to make humans what they are today.
We might never learn what happened to the Neanderthals, or the enigmatic Denisovans, and why they died out while humans survived and became the dominant species on the planet. What we can now say with some confidence is that human ancestors apparently were as interested in sex as modern humans are, and weren’t particularly troubled about who — or what species — they were having sex with, either.