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DAVID REICH (1974) is a professor at Harvard Medical School and a geneticist specializing in studying ancient human DNA.

Who We Are And How We Got Here
by David Reich
Vintage Random House, 2018

This book by the Harvard geneticist David Reich explores the molecular biology of ancient DNA and the new science of the human past, according to the subtitle of the book. Written with the lay audience in mind, I still feel that it is a dense volume to read and it helps if the reader has some background in DNA and molecular biology. For me as a biochemist and teaching human heredity at college level, it is an awesome book to have and read from a geneticist at the front lines of studying ancient DNA and having grown up in the modern area of whole genome science and the complete Human Genome Project. David Reich is actively involved in some ground breaking publication in understanding both ancient human DNA as well as the sequencing of Neanderthal and Denisovan genomes, both human lineages that have co-existed for at least 200,000 years in Eurasia, but who both disappeared around 40,000 year ago. Today modern humans, us, are the only surviving homo species. So reading his account how to properly understand popular ancestry testing as well as how to make sense of small percentage of Neanderthal and Denisovan genomes in modern non-African people is illuminating and fascinating at once. One really valuable piece of information comes early on when he explains that going back more than 10 generations, we have many ancestors in our family tree that leave no genetic trace in our own genome. This view of going back more than 500 years, namely thousands of years, has always puzzled me how to think about it. So here we have a situation where some 50,000 years ago we all today share the same ancestors (our family trees collapse into one human tree) and yet there is no specific ancestor we can pinpoint from our own genome sequence that far back in time. We are simply members of the same species. Only our immediate ancestors over the last few hundred years can be successfully trace, if we are lucky from written records. In this respect I also encourage the the reader to check out the PBS series 'Finding Your Roots' with Henry Louis Gates that masterfully demonstrates the use of genetic genealogy of tracking lost or unknown great-great parents.