From the time I was a boy, I wanted to know everything – from watching minute creatures living in lakes and ponds to wondering what exists at the far horizons of the universe. So once I started reading the different sciences, I never stopped. And always, always, I’ve looked most expectantly to the future where new discoveries are waiting.
But at 75 years old, that window to the future has begun to close for me. That’s why I was so happy when I discovered geneticist David Reich’s 2018 book, Who We Are and How We Got Here. For in the study of human origins, the future is now rushing in the front door.
Do you remember how in 2010 scientists stunned the world with the revelation that all people in the world, with the exception of those of sub-Saharan African origin, have Neanderthal DNA? Well, after 2010 we didn’t hear a lot more from the geneticists, but that’s because they were were preoccupied with interpreting masses of new evidence.
The leader of the 2010 project was Svante Paabo at the Max Plank Institute in Germany, but early on he invited David Reich in the USA to join his team. Reich welcomed the opportunity, and he and many others have continued this genetic exploration. I’ll let him explain:
In 2016, the lid of Pandora’s box opened wide and a whole mob of ancient ghosts whirled out. My laboratory assembled genometric data from fifty-one ancient modern humans in Eurasia, most of them from Europe, who lived between forty-five thousand and seven thousand years ago.
Reich introduces us to ‘ghost races’ from the past.
For example, if you could take a time machine back to Europe about 8,000 years ago, when it was re-populating as the ice-age glaciers receded north, what would the hunter-gatherer humans you would meet look like? The typical person, Reich tells us, would have dark hair, dark skin and blue eyes. Light skin did not arrive in Europe until farming people from the Middle-East and herding people from the north Asian steppes, migrated there later. But none of those people had blue eyes.
Those dark people are gone now, but some of their genes – their blue-eyed ghosts – haunt modern Europe
Have you ever read Dan Brown’s history of the American west, told from the perspective of native people – Bury My Heart at Wounded Knee? In that book there are many photos of famous native people – Sitting Bull, Red Cloud, etc – that made me wonder at the remarkable European features I was seeing, that are not common at all in north Asians. I assumed that they were the result of early interbreeding with Europeans.
Not so, says Reich.
Based on DNA from ancient human fossils found in Siberia, he says a ‘ghost race’ of people lived in Siberia – the ‘Ancient North Eurasians’. But their DNA doesn’t exist in the people who occupy Siberia now. Where did they go? They appear to have split into two groups, one going east across the Bering Strait into North America, the other travelling west across north Asia until they entered northern Europe. The result is that today some native people of America and the people of northern Europe share about 20% of their DNA. They are genetic cousins.
South America – for a long time the assumption has been that north Asian people travelling through the ice-free corridor in the American north-west entered the Americas there, then gradually moved south, continuing until they reached the southern tip of South America. They were the ancestors of everyone in the Americas, simple as that.
But the DNA evidence has produced surprises. In South America Reich says geneticists met their biggest surprise of all- a number of native peoples in the south Amazon region of Brazil share DNA with people in Australasia – with Andaman islanders, Australian aborigenes, and the people of New Guinea. That DNA represents another ghost race, that Reich terms ‘Population Y’. He speculates that people from Australasia may have preceded today’s ‘First Americans’ (the term he uses for native peoples) in South America, but have been almost completely replaced by them, leaving only this genetic trace. But he admits that genetic scientists simply don’t know how this has happened.
Africa is the most enigmatic continent. There is more genetic difference among African peoples than there is anywhere else in the world, but there has been almost no ancient African DNA to examine because DNA deteriorates too much in hot environments. However, as the technology for reconstructing DNA improves this is beginning to change, and that has begun to produce many other surprises, too complex for me to get into here.
When I read these things, I wanted to stand up and cheer for David Reich and his colleagues. That’s what I’m trying to do here.
But I’ve barely touched the surface of what Who We Are and How We Got Here has to offer. I’ve said nothing about India, China, or the South Pacific, each of which have produced fascinating new insights. There are ghost races everywhere. Reich warns us that it is time to give up on this idea that there are any pure races – humanity has been mixing regularly for a very long time.
Yes, the science of genetics is exploding with new knowledge about ‘who we are’. If you want to know who you are, you need to read David Reich’s book.