Who We Are and How We Got Here by David Reich review – new findings from ancient DNA Using advances in DNA sequencing, the geneticist shows the effects of migrations and the mongrel nature of humanity in this fascinating study
Peter Forbes
Thu 29 Mar 2018 05.00 EDT
Last modified on Fri 30 Mar 2018 19.10 EDT
Citizen of nowhere ... the geneticist David Reich. Photograph: Howard Hughes Medical Institute, Bizuayehu Tesfaye
“Arrival of Beaker folk changed Britain for ever, ancient DNA study shows”, ran a Guardian headline in February, concerning the people whose ancestry lay in central Europe and further east to the steppes. Now comes the author of that study, Harvard geneticist David Reich, with his book that gives us, at last, the first draft of a true history of the last 5,000 years.
Genetics first started to complement the work of archaeologists and linguists in the 1990s in the work of Reich’s mentor, the Italian-born population geneticist Luca Cavalli-Sforza. But genetics was the poor relation at the time because its data was so thin. Not any more. The genome is a palimpsest that retains strong traces of the past, so current populations can reveal something of previous population movements. What has changed everything has been the ability, beginning as recently as 2010, to sequence DNA directly from ancient human remains, sometimes as old as 40,000 years.
A double “Beaker” grave excavated at Trumpington Meadows, Cambridgeshire, and dating to c2000-1950 BC. Photograph: Dave Webb, Cambridge Archaeological Unit Reich revisits recent breakthroughs in charting the early history of humans, but his most dramatic discoveries have been made in the more recent past. Most significant developments in human history have happened in the last 10,000 years since the retreat of the great ice sheet, and for Europe the past 5,000 years are crucial. Although studies in ancient DNA have now leapfrogged archaeology and linguistics to become the best source of knowledge on prehistoric human populations and migrations, they dovetail with those disciplines in a three-way corroborative process.
Reich’s work can finally answer the tantalising question first posed by an British civil servant, Sir William Jones. In 1786, he discovered the kinship of Sanskrit and ancient Greek. This led to the recognition of the vast Indo-European language family – which includes the Germanic, Celtic, Italic, near eastern (Iranian) and north Indian languages (Hindi, Urdu, Bengali, Punjabi, Marathi, etc) – but not to any consensus on how this might have occurred. Reich has now shown that the Indo-European languages and the largest single component of the genetic makeup of Europe and north India today stem from migrations around 5,000 years ago from the vast Steppe, the grass plains bordering the Black and Caspian seas.
Most people of European descent have close genetic and linguistic ties with near eastern and north Indian peoples
These people were pastoral nomads who drove wheeled vehicles, rode domesticated horses and began to use dairy products – a package that was to guarantee their dominance wherever they went. Their migrations were the engine that powered the bronze age. Homer described a society in which warlords gained prestige and wealth through plunder and rape. It is not pretty, but is highly congruent with what we now know of the Yamnaya (the Beaker people represented the far western wave of Yamnaya migrations). Of theirs and other such male-dominant migrations, Reich drily comments: “Males from populations with more power tend to pair with females from populations with less.”
He deals commendably with the abuses that have been made of stories of origins – notably Nazi ideology – and recognises that some ideologues will want to exploit and contest his findings, too. It’s intriguing to know that most people of European descent have close genetic and linguistic ties with near eastern and north Indian peoples, but what is the global picture and what are the implications of these new findings?
The overriding lesson ancient DNA teaches is that the population in any one place has changed dramatically many times since the great human post-ice age expansion, and that recognition of the essentially mongrel nature of humanity should override any notion of some mystical, longstanding connection between people and place. We are all, to use Theresa May’s derisive label, “citizens of nowhere”. The Beaker people replaced 90% of the population of Britain around 4,500 years ago. Related to this is the knowledge that all life, from its beginnings, has been an essentially improvisatory, impure process. As Reich puts it: “Ideologies that seek a return to a mythical purity are flying in the face of hard science.”
His findings have important medical implications, too. For instance, his research in India has shown the profound consequences of caste-system inbreeding. There is an abundance of recessive diseases – both partners in some couples carry mutant genes from way back in the lineage. In fact, such populations make gene hunting easier because genes causing recessive conditions come with characteristic markers.
Reich’s overall picture will, in time, acquire much greater detail – just as Darwin’s great study was a beginning not an end – but we should be grateful to him and his large team of co-workers (including his wife, science writer Eugenie Reich, who had a big role in the book’s creation) for putting the essential story before us now. It is thrilling in its clarity and its scope.