Would you kill them or make love to them?
You have seen him stealing glances at you on the sly. You think him kind of cute. The fact that he is not the same species as you, makes it all the more kinky. You sneak out. You meet him in a cave. You make love. You fall pregnant. You pretend it is one of your tribes’. There are suspicions, but you get away with it. Almost. If it wasn’t for those pesky anthropologists. 100,000 years later, a scientist finds your great-great-great-great-great- granddaughter’s ancient bones in Siberia, runs tests and announces triumphantly to the entire world that you slept with a Neanderthal.
Don’t worry, everyone did it
So we all belong to the only group of hominins ( a hominin is the group consisting of modern humans, extinct human species and all our immediate ancestors) on the planet today. However, there was a time on the planet, when we were not alone, there were other hominin species wandering around Eurasia.
Your ancestors met them, and shall we say, got to know them in the biblical sense. They were Neanderthals (we’ve known about them since the 1800s)and Denisovans (we only know about them since 2008). How do we know that we slept with them? Because they form part of our DNA. Indeed, part of our success as a species is due to our interbreeding with those other hominins. Living people of European and East Asian descent have between 1 to 2% Neanderthal DNA in their genes. Whilst there is up to 6% Denisovan DNA in some populations of Melanesians in the southwest Pacific.
So what good stuff did we get from them?
STAT2 is part of our immune signalling system and HYAL2 is involved in skin-cell repair after sunburn. These genes are examples of a phenomenon known as adaptive introgression, when genetic material from one species moves into the gene pool of another species and then is selected and sticks around. There can be a downside, introgressed genes which were once beneficial can become less so over time as the environment in which natural selection is taking place changes. For example, we have inherited a gene that increases the risk of blood clots.
Why are these other hominins not around anymore?
Anthropologists reckon climate change and competition from modern humans caused their downfall. But, incredibly, considering our history, there is no evidence of violence between us and them. So, some researchers have suggested that is was increased migration of humans from Africa into Eurasia that pushed Neanderthals into extinction, just a numbers game. Interbreeding may have been rampant and so contributed to decreased genetic variation. So, now we stand alone? Or do we? Not really, because parts of them live on today in us.