New book explores the disquieting — and violent — past written in our genes.
- Who We Are and How We Got Here: Ancient DNA and the New Science of the Human Past
- Pantheon (2018)
This book is fascinating, surprising and disquieting, in roughly equal portions. The fascination arises from a remarkable new science making discoveries almost daily. The surprises are in discoveries that overturn what seemed like settled knowledge about humanity’s evolution and spread.
And the disquiet stems from the implications. If history is written by the winners, the history in our DNA is darker and bloodier than anything imagined in Game of Thrones.
David Reich is a specialist in ancient DNA and the head of the Reich Lab at Harvard. He and his colleagues can read whole genomes in a single bone, faster and more cheaply than anyone would have thought possible in the 1990s.
The genetics of ancient-DNA analysis are complex, and Reich doesn’t dumb down the technical aspects. Sometimes his explanations baffle more than enlighten. But he shows that it’s a wise population that knows its ancestors: we of European descent, for example, are a recent mixture of four different peoples as unlike one another as modern Europeans are from modern East Asians.
Other surprises are coming thick and fast. Reich himself was surprised to find that modern non-African humans derive about two per cent of their ancestry from Neanderthals; we’re also remote descendants of the Denisovans, a human group we didn’t even know existed until 2008. The Denisovans also inter-bred with their distant cousins the Neanderthals and were among the ancestors of South Asians, New Guineans, Australians and Melanesians. And the DNA of the Australians’ ancestors, Reich tells us, has also been found in Brazil’s Amazon region — churning up the prehistory of the Americas and hinting at as many as four distinct migrations from Asia.
Predicting ‘ghost populations’
One striking result of this high-tech genealogy is the ability to predict populations whose bones we haven’t found yet. One such group was the Ancient North Eurasians, whose DNA was found in both modern Europeans and Indigenous Americans. Well after that “ghost population” was identified, the 24,000-year-old bones of an Ancient North Eurasian were found in a cave near the Siberian village of Mal’ta.
We know more about the genetic history of “West Eurasia” — Europe from the Urals to the sea — than of the rest of the world. That’s because European bones are more accessible than those from Asia, Africa and the Americas.
But it’s also a cultural and political problem: China won’t send its bones outside the country, and Indigenous peoples of the Americas take a dim view of strangers messing with their ancestors’ remains. Reich praises the wisdom of Danish DNA researcher Eske Willerslev, who has persuaded some Indigenous groups that ancestral DNA can strengthen their claims to their land.