Who We Are and How We Got Here is a 2018 book on the contribution of genome-wide ancient DNA research to human population genetics by the geneticist David Reich. He describes discoveries made by his group and others, based on analysis and comparison of ancient and modern DNA from human populations around the world. Central to these is the finding that almost all human populations are mixtures resulting from multiple population migrations and gene flow.
Several reviewers have praised the book for clearly describing pioneering work in a cutting-edge field of study.[1][2] It has been criticized by numerous scientists and scholars for its handling of race,[3] though other commentators observe that nothing it says should give racists any comfort.[4][5]
Context
David Reich is a geneticist who has studied ancient human genomes, comparing their patterns of mutations to discover which populations migrated and mixed throughout prehistory.[6] He was mentored by the population geneticist Luca Cavalli-Sforza, who from 1960 pioneered the attempt to match the study of human prehistory by archaeology and linguistics, using the limited genetic data available at that time.[4]
Who We Are and How We Got Here was published by Oxford University Press in 2018, ISBN978-0-19-882125-0. It is credited to David Reich alone, but he explains in the acknowledgements that the book grew from a detailed collaboration with his wife, Eugenie Reich.
The book is illustrated with monochrome maps, diagrams, and timelines. There are no photographs.
Summary
Since 2010, population geneticists have been able to sequence ancient human DNA, recovering complete genomes,[4] in contrast to earlier approaches which relied on the far more abundant (and hence more easily recovered) mitochondrial DNA, which is present in many copies in each cell, and transmitted only via the maternal line. That early work gave what Reich calls the "exciting" result that all modern humans are related to "Mitochondrial Eve", a woman who lived in Africa only about 160,000 years ago.[7][8]
The whole genome recovery technique, using the especially hard bone from the inner ear of ancient skeletons — along with the genomes of modern people from different parts of the world, including especially some isolated populations — has made it possible to reconstruct prehistoric migrations and mixing of populations in the past 5,000 years, and to make reliable inferences about mixtures from much further back in time.[4] The new knowledge from genomics has overthrown many old assumptions about human origins.[4]
Much of the work has focused on Western Eurasia, where in 1786 Sir William Jones discovered that Sanskrit and ancient Greek were related languages. Linguists came to recognise the Indo-European family of languages, spanning Germanic, Celtic, Italic, Iranian and northern Indian languages, but without explaining how these came to be. Reich showed that modern populations in Europe and north India derive from mixing of native populations with Yamnaya people from the steppes north of the Black Sea and the Caspian Sea some 5,000 years ago, in separate migrations to the west and the east.[4][9]Corded ware culture described by archaeology corresponds to a stage in the westward migration.[4]
Reich observes that similar migrations and population mixtures characterise human prehistory on all continents.[4] Reich shows that people in Japan and Korea share some 80% of their DNA, implying migration; Polynesians migrated relatively recently, in just the past few thousand years, from the region of Taiwan. The evidence can upset long-held beliefs: Native American skeletons from 10,000 years ago do not appear to be related to the tribes living in those regions today who have been asking for the ancient bones to be returned to them for burial.[7]
The Neanderthals are extinct, but part of their genome survives: Reich notes that all present-day non Sub-Saharan Africans have at least 2% of Neanderthal ancestry. Reich explains that somewhere between 100,000 and 50,000 years ago, modern humans mated with Neanderthals, and their descendants carried those genes all over the world. An ancient skeleton from Romania had up to 9% Neanderthal DNA, so natural selection has been removing Neanderthal genes since those matings.[7]
Author and intellectual Jared Diamond, in the New York Times, notes that geneticists can now go far beyond studying the personal ancestries of participants in National Geographic's Genographic Project, which looked at small sections of their parents' DNA, namely their mother's mitochondrial DNA and their father's Y chromosome. By looking at DNA from ancient bones, Reich can recover whole genomes. Diamond warns readers not to expect an oversimplified story:[7]
Population genetics is a complicated, fast-moving field with many uncertainties of interpretation. To tell that story to the broad public, and not just to scientists reading specialty journals, is a big challenge. Reich explains these complications as well as any geneticist could; others rarely even try.[7]
Peter Forbes, in The Guardian, calls the book "thrilling in its clarity and its scope."[4] In Forbes's view, Reich handles racist abuses of human origin stories, such as Nazi ideology, "commendably". Forbes writes that Reich explains how ancient DNA teaches a single general lesson, that the human population of any particular place has repeatedly changed since the last ice age. Any supposed "mystical, longstanding" link between some people and a place based on some kind of racial purity (as reflected in the Nazi slogan of "blood and soil"), is in Reich's words "flying in the face of hard science".[4]
Clive Cookson, in the Financial Times, writes that one of the first and most surprising impacts of genomics is in human prehistory, and Reich is the first leading practitioner to write a popular book about this. Cookson calls the book[1]
a marvelous synthesis of the field: the technology for purifying and decoding DNA from old bones; what the findings tell us about the origins and movements of people on every inhabited continent; and the ethical and political implications of the research.[1]
Cookson notes that Reich dismisses worries that DNA evidence of differences between populations is "racism in genetic clothing",[1] and that on the contrary, the "unsuspected degree of mixing"[1] in every part of human history makes old ideas of racial purity "absurd".[1]
Bell-shaped Beaker pots, found in Western Europe c. 2900–1800 BC
The archaeologist and geneticist Turi King, in Nature, writes that Reich's laboratory "has developed some of the most sophisticated statistical and bioinformatics techniques available. Using computers, they painstakingly reconstruct genomic information from fragments of DNA from ancient individuals. They then drill down in search of a new understanding of human history." King notes that Reich's group helped to show that "Neanderthals interbred with the ancestors of all modern humans descended from Europeans, Asians and other non-Africans." Their work is showing the "tremendous degree to which populations globally are blended, repeatedly, over generations." King notes, too, that Reich reflects on the dangers of misinterpretation by racists, who "pick and choose results", or others who opt to "sweep [genetic] differences under the carpet". But, King argues, echoing Reich, we do need "a non-loaded way to talk about genetic diversity and similarities in populations", and Reich has begun to do that.[11]
The economist Tyler Cowen calls the book "truly excellent, readable and informative". Cowen insists it is "a science book, not a 'race book'", stating that although it has engendered "some public controversy", he is confident that no attentive reader could feel "affirmed in racist beliefs".[5]
Admixture plot of Western African Pygmies and their Bantu neighbours. This shows that Pygmy populations contain substantial amounts of Bantu genetic material, whereas Bantu populations have very little Pygmy ancestry.
A review by Razib Khan, who is cited in the book, recommends the book to a wide audience, arguing that it "catches [one] up to the state-of-the-art knowledge that we have in terms of human history, deep and prehistoric." He includes experts in that audience: "I’ve talked to plenty of people who work in evolutionary genomics who are not totally up-to-speed on the ancient DNA revolution. They too would benefit from reading Who We Are and How We Got Here front to back. I know people who work in the field of cultural evolution, who would also benefit from reading Who We Are and How We Got Here. I know behavior geneticists who would benefit from reading Who We Are and How We Got Here. And so forth." Khan concedes that the book "is not rich with the same stylistic flourish and engagement as one might find in a popularization by Steven Pinker or Richard Dawkins" but that it is a "serious book that is earnest in focusing on the substance of the science first."[2]
The paleogenomics researcher María C. Ávila Arcos reviewed the book in Science magazine, arguing that "troubling traces of biocolonialism undermine an otherwise eloquent synthesis of ancient genome research."[12] She calls Reich's account graceful, combining his personal opinions with "hard science"[12] (Reich's phrase). She accepts that the book is "scientifically solid and comprehensive",[12] but argues that it "raises some concerns",[12] since in her view Reich overlooks the conflict of interest between the needs of researchers to gather ancient human DNA specimens and the rights of the often marginalised populations that descend from those ancestors.[12]
The anthropologist John Hawks, writing in the Wall Street Journal, observes that Reich was surprised that the "concordance of near-mythological history with genetic fact"[13] in the migrations in India was "a potential political bombshell";[13] he notes that Reich avoided it by not talking about "Indo-European invaders at all",[13] writing only that "No group in India can claim genetic purity".[13] In Hawks's view, Reich "seems a contradiction: Rising to the pinnacle of human genetics, he nonetheless exhibits incredible naiveté"[13] in affairs such as when German scientists withdrew from a paper that seemed to them "uncomfortably close to pre-Nazi racial theories",[13] or when Native American specimen donors wished to limit the use of their DNA. Hawks argues that science needs to help people to see the humanity of the dead ancestors, and finds Reich's approach potentially dehumanizing.[13]
The scholar of humanities Barry Wood writes that the book is "densely-packed", not sparing on explanations of advanced techniques, but allowing the determined reader to grasp the methods of genomic analysis. He comments that the "tradeoff" for this detail is "a certain lack of continuity". He notes that Reich argues that migration is what his analysis illuminates best, but comments that Reich's discrete studies of human migrations do not yet add up to "a sequential narrative of the peopling of the earth".[14]
The archaeologist Daniela Hofmann describes the book as clear and accessible, but calls Reich "not shy of controversy" and states that the book is "very much an advertisement for Reich's research agenda" and "unashamedly partial".[15]
According to computational biologist Hussein Mohsen, Reich's examples "conflated ancestry with race, relied on the quantitative reductionism of averages, and failed to address the everyday ramifications of pathologizing socially constructed (racial or ancestral) categories to which millions of human beings belong or were historically forced to."[16] In contrast to Reich's analysis, Mohsen cites the open letter "How Not To Talk About Race And Genetics" as an accurate representation of "the complexity of the race concept and stark limitations of quantitative genetics to grasp its fluid histories."[16]
Related Research Articles
Svante Pääbo is a Swedish geneticist and Nobel Laureate who specialises in the field of evolutionary genetics. As one of the founders of paleogenetics, he has worked extensively on the Neanderthal genome. In 1997, he became founding director of the Department of Genetics at the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany. Since 1999, he has been an honorary professor at Leipzig University; he currently teaches molecular evolutionary biology at the university. He is also an adjunct professor at Okinawa Institute of Science and Technology, Japan.
Archaeogenetics is the study of ancient DNA using various molecular genetic methods and DNA resources. This form of genetic analysis can be applied to human, animal, and plant specimens. Ancient DNA can be extracted from various fossilized specimens including bones, eggshells, and artificially preserved tissues in human and animal specimens. In plants, ancient DNA can be extracted from seeds and tissue. Archaeogenetics provides us with genetic evidence of ancient population group migrations, domestication events, and plant and animal evolution. The ancient DNA cross referenced with the DNA of relative modern genetic populations allows researchers to run comparison studies that provide a more complete analysis when ancient DNA is compromised.
The Yamnaya culture or the Yamna culture, also known as the Pit Grave culture or Ochre Grave culture, was a late Copper Age to early Bronze Age archaeological culture of the region between the Southern Bug, Dniester, and Ural rivers, dating to 3300–2600 BCE. It was discovered by Vasily Gorodtsov following his archaeological excavations near the Donets River in 1901–1903. Its name derives from its characteristic burial tradition: Я́мная is a Russian adjective that means 'related to pits ', as these people used to bury their dead in tumuli (kurgans) containing simple pit chambers.
Researchers have investigated the relationship between race and genetics as part of efforts to understand how biology may or may not contribute to human racial categorization. Today, the consensus among scientists is that race is a social construct, and that using it as a proxy for genetic differences among populations is misleading.
Human genetic variation is the genetic differences in and among populations. There may be multiple variants of any given gene in the human population (alleles), a situation called polymorphism.
David Emil Reich is an American geneticist known for his research into the population genetics of ancient humans, including their migrations and the mixing of populations, discovered by analysis of genome-wide patterns of mutations. He is professor in the department of genetics at the Harvard Medical School, and an associate of the Broad Institute. Reich was highlighted as one of Nature's 10 for his contributions to science in 2015. He received the Dan David Prize in 2017, the NAS Award in Molecular Biology, the Wiley Prize, and the Darwin–Wallace Medal in 2019. In 2021 he was awarded the Massry Prize.
The genetic history of Europe includes information around the formation, ethnogenesis, and other DNA-specific information about populations indigenous, or living in Europe.
Early human migrations are the earliest migrations and expansions of archaic and modern humans across continents. They are believed to have begun approximately 2 million years ago with the early expansions out of Africa by Homo erectus. This initial migration was followed by other archaic humans including H. heidelbergensis, which lived around 500,000 years ago and was the likely ancestor of Denisovans and Neanderthals as well as modern humans. Early hominids had likely crossed land bridges that have now sunk.
The Denisovans or Denisova hominins(di-NEE-sə-və) are an extinct species or subspecies of archaic human that ranged across Asia during the Lower and Middle Paleolithic. Denisovans are known from few physical remains; consequently, most of what is known about them comes from DNA evidence. No formal species name has been established pending more complete fossil material.
Interbreeding between archaic and modern humans occurred during the Middle Paleolithic and early Upper Paleolithic. The interbreeding happened in several independent events that included Neanderthals and Denisovans, as well as several unidentified hominins.
Carlos D. Bustamante is an American population geneticist, academic, and entrepreneur. He is currently chief executive officer of Galatea Bio, Inc., a company he founded when a professor at Stanford University School of Medicine.
Ust'-Ishim man is the term given to the 45,000-year-old remains of one of the early modern humans to inhabit western Siberia. The fossil is notable in that it had intact DNA which permitted the complete sequencing of its genome, one of the oldest modern human genomes to be so decoded.
Eran Elhaik is an Israeli-American geneticist and bioinformatician, an associate professor of bioinformatics at Lund University in Sweden and Chief of Science Officer at an ancestry testing company called Ancient DNA Origins owned by Enkigen Genetics Limited, registered in Ireland. His research uses computational, statistical, epidemiological and mathematical approaches to fields such as complex disorders, population genetics, personalised medicine, molecular evolution, genomics, paleogenomics and epigenetics.
Recent human evolution refers to evolutionary adaptation, sexual and natural selection, and genetic drift within Homo sapiens populations, since their separation and dispersal in the Middle Paleolithic about 50,000 years ago. Contrary to popular belief, not only are humans still evolving, their evolution since the dawn of agriculture is faster than ever before. It has been proposed that human culture acts as a selective force in human evolution and has accelerated it; however, this is disputed. With a sufficiently large data set and modern research methods, scientists can study the changes in the frequency of an allele occurring in a tiny subset of the population over a single lifetime, the shortest meaningful time scale in evolution. Comparing a given gene with that of other species enables geneticists to determine whether it is rapidly evolving in humans alone. For example, while human DNA is on average 98% identical to chimp DNA, the so-called Human Accelerated Region 1 (HAR1), involved in the development of the brain, is only 85% similar.
In archaeogenetics, the term Ancient North Eurasian (ANE) is the name given to an ancestral component that represents the lineage of the people of the Mal'ta–Buret' culture (c. 24,000 BP) and populations closely related to them, such as the Upper Paleolithic individuals from Afontova Gora in Siberia. Genetic studies indicate that the ANE are closely related to the Ancient North Siberians (ANS) represented by two ancient specimens from the preceding Yana Culture (c. 32,000 BP). The ANE can either be considered to descend from the earlier ANS population, or that both ANE and ANS are closely related, albeit differentiated, sister lineages, with both having originated from an 'Early West Eurasian' hunter-gatherer lineage (represented by Kostenki-14, c. 40,000 BP), which absorbed an 'Early East Eurasian' population (represented by the Tianyuan man, c. 40,000 BP). The ANS and ANE each derive between 16% to 35% of their ancestry from an Early East Eurasian lineage and between 65% to 84% from an Early West Eurasian lineage.
Genetic studies on Neanderthal ancient DNA became possible in the late 1990s. The Neanderthal genome project, established in 2006, presented the first fully sequenced Neanderthal genome in 2013.
Denny is an ~90,000 year old fossil specimen belonging to a ~13-year-old Neanderthal-Denisovan hybrid girl. To date, she is the only first-generation hybrid hominin ever discovered. Denny’s remains consist of a single fossilized fragment of a long bone discovered among over 2,000 visually unidentifiable fragments excavated at the Denisova Cave in the Altai Mountains, Russia in 2012.
Paleogenomics is a field of science based on the reconstruction and analysis of genomic information in extinct species. Improved methods for the extraction of ancient DNA (aDNA) from museum artifacts, ice cores, archeological or paleontological sites, and next-generation sequencing technologies have spurred this field. It is now possible to detect genetic drift, ancient population migration and interrelationships, the evolutionary history of extinct plant, animal and Homo species, and identification of phenotypic features across geographic regions. Scientists can also use paleogenomics to compare ancient ancestors against modern-day humans. The rising importance of paleogenomics is evident from the fact that the 2022 Nobel Prize in physiology or medicine was awarded to a Swedish geneticist Svante Pääbo [1955-], who worked on paleogenomics.
Early Indians: The Story of Our Ancestors and Where We Came From is a 2018 nonfiction book written by Indian journalist Tony Joseph, that focuses on the ancestors of people living in South Asia today. Joseph goes 65,000 years into the past—when anatomically modern humans, first made their way from Africa into the Indian subcontinent. The book relies on research findings from six major disciplines: history, archaeology, linguistics, population genetics, philology, and epigraphy, and includes path-breaking ancient DNA research of recent years. It also relies on the extensive study titled "The Genomic Formation of Central and South Asia", co-authored by 92 scientists from around the world and co-directed by geneticist David Reich of Harvard Medical School, in which ancient DNA was used. The book has been translated into Tamil, Hindi, Odia, Telugu, Marathi, Malayalam, Gujarati, and other languages.
Jennifer Anne Raff is an American geneticist and an associate professor of Anthropology at the University of Kansas. She specializes in anthropological genetics relating to the initial peopling of the Americas and subsequent prehistory of Indigenous populations throughout North America. She is the President of the American Association of Anthropological Genetics. Alongside her research, Raff is a science communicator who writes and gives public talks about topics in science literacy.
1 2 3 4 5 Ávila Arcos, María C. (20 April 2018) [Published online 17 April 2018]. Thompson, Valerie (ed.). "Wielding new genomic tools wisely". Book review. Science. 360 (6386): 274. Bibcode:2018Sci...360..274A. doi:10.1126/science.aat3780. S2CID13986313. Troubling traces of biocolonialism undermine an otherwise eloquent synthesis of ancient genome research
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