Who We Are and How We Got Here: Ancient DNA and the New Science of the Human Past

by David Reich

in that we now know, from ancient DNA, that the people who live in a particular place today almost never exclusively descend from the people who lived in the same place far in the past.

what the study of ancient DNA has now shown is that the past was no less complicated than the present. Human populations have repeatedly turned over.

Today, many people assume that humans can be grouped biologically into “primeval” groups, corresponding to our notion of “races,” whose origins are populations that separated tens of thousands of years ago. But this long-held view about “race” has just in the last few years been proven wrong—and the critique of concepts of race that the new data provide is very different from the classic one that has been developed by anthropologists over the last hundred years. A great surprise that emerges from the genome revolution is that in the relatively recent past, human populations were just as different from each other as they are today,

ancestors is almost a thousand times greater than the number of ancestral stretches of DNA in a person’s genome, so it is a certainty that each person has not inherited any DNA from the great majority of his or her actual ancestors.

In most parts of the genome, Africans are more genetically diverse than non-Africans

One of the profound implications of the Denisovan discovery was that East Eurasia is a central stage of human evolution and not a sideshow as westerners often assume.

Ron Pinhasi, working in Dublin, showed that the mother lode of DNA is found in the cochlea, the snail-shaped organ of hearing.

This meant that the high genetic substructure that had previously characterized West Eurasia collapsed into the present-day very low level of genetic differentiation by the Bronze Age. It is an extraordinary example of how technology—in this case, domestication—contributed to homogenization, not just culturally but genetically. It shows that what is happening with the Industrial Revolution and the information revolution in our own time is not unique in the history of our species.

The findings of the ancient DNA revolution suggest that the mixtures will continue. Mixture is fundamental to who we are, and we need to embrace it, not deny that it occurred.

This strange link to present-day Sardinians kept turning up.

Discussions of the Corded Ware culture and migration in the same breath ring particularly loud alarm bells because of Kossinna’s and the Nazis’ attempt to use the Corded Ware culture to construct a basis for national German identity.29 While we were in the final stages of preparing a paper for submission in 2015, one of the German archaeologists who contributed skeletal samples wrote a letter to all coauthors: “We must(!) avoid…being compared with the so called ‘siedlungsarchäologische Methode’ from Gustaf Kossinna!”

The association between steppe genetic ancestry and people assigned to the Corded Ware archaeological culture through graves and artifacts is not simply a hypothesis. It is now a proven fact.

Indian jati groups living side by side in the same village is typically two to three times higher than the genetic differentiation between northern and southern Europeans.39 The truth is that India is composed of a large number of small populations.

Archaeological, linguistic, and genetic data taken together have suggested that around five thousand years ago, mainland East Asian farming spread to Taiwan, where the deepest branches of the Austronesian language family are found.

On the one side there are beliefs about the nature of the differences that are grounded in bigotry and have little basis in reality. On the other side there is the idea that any biological differences among populations are so modest that as a matter of social policy they can be ignored and papered over. It is time to move on from this paralyzing false dichotomy and to figure out what the genome is actually telling us.

If as scientists we willfully abstain from laying out a rational framework for discussing human differences, we will leave a vacuum that will be filled by pseudoscience, an outcome that is far worse than anything we could achieve by talking openly.