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Troubling traces of biocolonialism undermine an otherwise eloquent synthesis of ancient genome research

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

David Reich
362 pp.
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In Who We Are and How We Got Here, David Reich gracefully describes how recent advances in genomics have enabled the study of ancient genomes and how this, in turn, has significantly affected the study of the evolutionary and demographic history of our species. With a pleasant narrative style that immediately engages both scientists and nonscientists, the book describes the technological and statistical advances that have allowed researchers to read the genomes of humans, past and present.

The author is in a privileged position to convey the progress and major milestones achieved in the burgeoning field of ancient genomics because his research group has been a main player in this arena since the beginning. This means, of course, that the book disproportionately highlights work from his lab, as Reich himself freely acknowledges. (Much of this progress has been made possible by a custom DNA capture kit that, as of now, cannot simply be ordered by other researchers. Access to such kits, at a reasonable cost, would greatly enhance the ability of other groups to produce methodologically consistent data.)

Combining personal views and “hard science,” Who We Are and How We Got Here takes the reader on a journey from the dawn of our species to more recent events that have shaped our current population structure, all in the context of the knowledge generated by comparing the DNA of ancient and modern human populations. Throughout the book, Reich illustrates how continuous gene flow is the norm, not the exception, in the history of our species. “Mixture is fundamental to who we are,” he writes. “[W]e need to embrace it, not deny it occurred.”

The book eloquently addresses what ancient DNA has revealed about these mixing events, from the interbreeding between our ancestors and the Neandertals and Denisovans 50,000 to 60,000 years ago to the effects of European colonization of the Americas, which gave rise to admixed African American and Latino populations. It describes the migrations and mixing events that formed the population structure observed in Europe, India, and East Asia over the course of 10,000 years and explains how some current genetic variation can only be explained by past mixing with yet uncharacterized ancient populations, which Reich refers to as “ghost” populations.

Reich also proposes a controversial theory in which he suggests that modern human ancestors actually may have lived in Eurasia, not in Africa, calling Eurasia a “hothouse of human evolution.” According to this theory, ancestral humans, including Neandertals and Denisovans, descended from the African Homo erectus, left Africa for Eurasia, and later returned to serve as the founders of what would eventually evolve into modern humans. This provocative proposal is sure to generate debate.


In our quest to understand human origins, we must remain vigilant with regard to the ethical implications of such research.

Although scientifically solid and comprehensive, the book raises some concerns. Even though Reich devotes a substantial part of the book to discussing the implications of ancient DNA research, he overlooks some of the most profound issues inherent in this type of work, specifically with regard to the practices surrounding the collection and processing of human DNA samples.

Early in the book, for example, he writes that his goal is to build “an American-style genomics factory” to investigate ancient DNA. When one considers the social and historical context of the human populations that will be studied—many of which have been historically marginalized, colonized, and exploited—this statement becomes problematic. Such intentions could easily be perceived as a continuation of exploitation or biocolonialism.

An unfortunate analogy further highlights the problem. “We are … like explorers in the late eighteenth century, sailing to every corner of the globe,” he writes. During the era to which Reich refers, European adventurers indeed collected samples from around the world, but these specimens were usually taken without the consent of, or regard for, the communities to whom they rightfully belonged.

On several occasions, Reich reveals his frustration with policies and legislation that prohibit the exportation of samples or that restrict the study of human remains, but he fails to entertain the idea that such scenarios could represent opportunities to train local scientists and members of the communities from whence the samples came to conduct their own studies. Building local capacities would allow this kind of research to be truly democratic.

There is no doubt that Reich has changed the game when it comes to our understanding of human history. His book, however, misses critical opportunities to highlight some of the major ethical issues surrounding ancient DNA research.

About the author

The reviewer is at the International Laboratory for Human Genome Research, Juriquilla, Querétaro, Mexico.