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

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

A groundbreaking book about how technological advances in genomics and the extraction of ancient DNA have profoundly changed our understanding of human prehistory while resolving many long-standing controversies.Massive technological innovations now allow scientists to extract and analyze ancient DNA as never before, and it has become clear--in part from David Reich's own...

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Title:Who We Are and How We Got Here: Ancient DNA and the New Science of the Human Past
Author:David Reich
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Who We Are and How We Got Here: Ancient DNA and the New Science of the Human Past Reviews

  • Willy C

    Willy Chertman

    03/29/2018

    "Who We Are and How We Got Here" is great book with some flaws. As a one-stop guide for catching up with the ancient DNA revolution, it is unequaled. It is also a refreshingly honest look into the life of a practicing prominent scientist in the age of large research labs and giant research consortiums.

    Coming along for the ride are some lucid explanations of many of the statistical tests used in ancestry mapping, like the Four Populations Test, and methods used to estimat

    Willy Chertman

    03/29/2018

    "Who We Are and How We Got Here" is great book with some flaws. As a one-stop guide for catching up with the ancient DNA revolution, it is unequaled. It is also a refreshingly honest look into the life of a practicing prominent scientist in the age of large research labs and giant research consortiums.

    Coming along for the ride are some lucid explanations of many of the statistical tests used in ancestry mapping, like the Four Populations Test, and methods used to estimate the dates of admixture events. For any outsider to the field who wants to be able to read the flood of research on ancient genomics with more comprehension, this is a valuable introduction.

    An incomplete list of some prominent themes with illustrative quotes:

    1. The most central theme of the book is probably the

    Reich views it as more powerful than radiocarbon dating, the most important scientific advance in archeology:

    * "These advances mean that whole-genome study of ancient DNA no longer requires screening large numbers of skeletal remains before it is possible to find a few individuals whose DNA can be analyzed. Instead, a substantial fraction of screened samples dating to the last ten thousand years can now be converted to working genome-wide data. The new methods have made it possible to analyze hundreds of samples in a single study. With such data, it is possible to reconstruct population changes in exquisite detail, transforming our understanding of the past."

    * "These days, human genome variation has surpassed the traditional toolkit of archaeology—the study of the artifacts left behind by past societies—in what it can reveal of changes in human populations in the deep"

    2.

    * It seems very likely that some genes in those admixture events were advantageous and have subsequently been selected for, while others have experienced have strong selection against them:

    * "One of the most striking genomic discoveries of the past few years is a mutation in a gene that is active in red blood cells and that allows people who live in high-altitude Tibet to thrive in their oxygen-poor environment. Rasmus Nielsen and colleagues have shown that the segment of DNA on which this mutation occurs matches much more closely to the Siberian Denisovan genome than to DNA from Neanderthals or present-day Africans.21 This suggests that some Denisovan relatives in mainland Asia may have harbored an adaptation to high altitude, which the ancestors of Tibetans inherited through Denisovan interbreeding. Archaeological evidence shows that the first inhabitants of the Tibetan high plateau began living there seasonally after eleven thousand years ago, and that permanent occupation based on agriculture began around thirty-six hundred years ago.22 It is likely that the mutation increased rapidly in frequency only after these dates, a prediction that will be possible to test directly through DNA studies of ancient Tibetans."

    * "at genes associated with the biology of keratin proteins, present-day Europeans and East Asians have inherited much more Neanderthal ancestry on average than is the case for most other groups of genes.23 This suggests that versions of keratin biology genes carried by Neanderthals were preserved in non-Africans by the pressures of natural selection, perhaps because keratin is an essential ingredient of skin and hair, which are important for providing protection from the elements in cold environments such as the ones that modern humans were moving into and to which Neanderthals were already adapted."

    3.

    That is, while Europeans are quite distinct from East Asians, who are themselves quite distinct from Native Americans/Amerindians, these continental groups are themselves the results of admixture events from previously distinct populations, who were themselves the result of mixture events. In other words, we [humans] are a mix all the way down.

    * "Today, the peoples of West Eurasia—the vast region spanning Europe, the Near East, and much of central Asia—are genetically highly similar. The physical similarity of West Eurasian populations was recognized in the eighteenth century by scholars who classified the people of West Eurasia as “Caucasoids” to differentiate them from East Asian “Mongoloids,” sub-Saharan African “Negroids,” and “Australoids” of Australia and New Guinea. In the 2000s, whole-genome data emerged as a more powerful way to cluster present-day human populations than physical features."

    * "Measured in this way, populations within West Eurasia are typically around seven times more similar to one another than West Eurasians are to East Asians. When frequencies of mutations are plotted on a map, West Eurasia appears homogeneous, from the Atlantic façade of Europe to the steppes of central Asia. There is a sharp gradient of change in central Asia before another region of homogeneity is reached in East Asia."

    * "What we had found was evidence that people in northern Europe, such as the French, are descended from a mixture of populations, one of which shared more ancestry with present-day Native Americans than with any other population living today."

    *

    4.

    This partially validates the predictions of some old-school (and often racist) anthropologists who thought genocide and conquering (ala Conan the Barbarian's line [

    ] ) was the most common cause of drastic change in the archaeological record but the deep origins of human populations as fundamentally mixed kind of pushes back against many of their other claims.

    * " The discovery that the Corded Ware culture reflected a mass migration of people into central Europe from the steppe was not just a sterile academic finding. It had political and historical resonance. At the beginning of the twentieth century, the German archaeologist Gustaf Kossinna was among the first to articulate the idea that cultures of the past that were spread across large geographic regions could be recognized through similarities in style of the artifacts they left behind. He also went further in viewing archaeologically identified cultures as synonymous with peoples, and he originated the idea that the spread of material culture could be used to trace ancient migrations, an approach he called the siedlungsarchäologische Methode, or “Settlement Archaeology.” ... Kossinna suggested that the cultural roots of the Germans and of Germanic languages today lay in the Corded Ware culture. In his essay “The Borderland of Eastern Germany: Home Territory of the Germans,” he argued that because the Corded Ware culture included the territories of Poland, Czechoslovakia, and western Russia of his day, it gave Germans the moral birthright to claim those regions as their own. "

    * "migrating farmers whose ancestors originated in the Near East spread over Europe with little mixture with the hunter-gatherers they encountered along the way, a sharp contrast to Luca Cavalli-Sforza’s model for the farming expansion into Europe that had been popular until this time and that emphasized extensive mixture and interaction with the local hunter-gatherers during the expansion. ."

    * "The extraordinary fact that emerges from ancient DNA is that just five thousand years ago, the people who are now the primary ancestors of all extant northern Europeans had not yet arrived"

    * "Prior to the explosion of ancient DNA data in 2015, most archaeologists found it inconceivable that the genetic changes associated with the spread of the Yamnaya culture could be as dramatic as the archaeological changes. "

    5.

    He views Lewontin, Gould and others as falling in this camp of 'deceptive with good intentions', and thinks that scientists should discuss the issue more head-on, as doing otherwise will concede the issue to scientists or informed bloggers who are less averse to speaking openly and speculatively on race.

    * Examples of political considerations impacting science:

    * "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!” He and several contributors then resigned as authors"

    * "At the time I felt that we were being prevented by political considerations from revealing what we had found."

    * "At a workshop on genetic studies of Native Americans that I attended in 2013, multiple researchers stood up from the audience to say that the response of the Karitiana, Havasupai, Navajo, and others had made them too wary to do any research Native Americans (including disease research)....the withdrawal of Navajo samples from out study was distressing, since they were among those with the very best documentation of informed consent..these individuals personals decisions to participate in the study were overruled by the tribal council's moratorium nine years later. "

    *"I have deep sympathy for the concern that genetic discoveries about differences among populations may be misused to justify racism. But it is precisely because of this sympathy that I am worried that people who deny the possibility of substantial biological differences among populations across a range of traits are digging themselves into an indefensible position, one that will not survive the onslaught of science. In the last couple of decades, most populations geneticists have sought to avoid contradicting the orthodoxy. When asked about the possibility of biological differences among human populations, we have tended to obfuscate.."

    * "To understand why it is no longer an option for geneticists to lock arms with anthropologists and imply that any differences among human populations are so modest that they can be ignored, go no further than the 'genome bloggers'...take pleasure in pointing out contradictions between the politically correct messages academics often give about the indistinguishability of traits across populations and their papers showing that this is not the way the science is heading. "

    6.

    Lots of mt-DNA in conjunction with only a few Y chromosomes implies a few men with many corresponding females, a marker of sexual inequality (via polygamy) and social inequality (the ability of a few men to monopolize the available women). This pattern is seen in many population replacements or admixture events:

    * "mixtures of highly divergent groups have happened time and again, homogenizing populations just as divergent from one another as Europeans, Africans, and Naive Americans. And in many of these great admixtures, a central theme has been the coupling of men with social power in one population and women from the other. "

    * "Comparison of Y-chromosome and mitochondrial DNA types that are highly different in frequency between African-Americans and Europeans also shows that by far the majority of the European ancestry in these populations comes from males, the result of social inequality in which mixed-race couplings were primarily between free males and females slaves...contribution of European American men to the genetic makeup of the present-day African American population is about 4 times that of the European American women....sociologist Orlando Patterson, he pointed out that fraction of the European ancestry in African Americans that came from males-- which if different from half is called ''sex bias"-- must have been far greater during the time of slavery. Since the civil rights movement in the USA in the mid-20th century, cultural changes have caused the sex bias to reverse, with more coupling between black men and white women. If we carried out DNA studies of African American skeletons from a hundred years ago, there is every reason to expect an even greater sex bias. "

    * "sex bias has been central to the history of our species. "

    * "great variability among males in the number of offspring produced means that by searching for genomic signatures of past variability in the number of children men have had, we can obtain genetic insights into the degree of social inequality in society as a whole, and not just between males and females. "

    * "Star Cluster analysis provides objective information about the importance of extreme inequalities in power at different points in the past. "

    * "on the Y chromosome, the studies found a pattern that was strikingly different. IN East Asians, Europeans, Near Easterners, and North Africans, the authors found many Star Clusters with common male ancestors living roughly 5 thousand years ago...powerful males in this period left an extraordinary impact on the populations that followed them-- more than in any previous period-- with some bequeathing DNA to more descendants today than Ghengis Khan. "

    *

    1. Neanderthal and out-of-Africa humans mixed and male offspring had reduced fertility

    2. We're mixes all the way down

    3. There can be REALLY strong endogamy for thousands of years: Ari ethnic group in Ethiopia, caste system in India,

    4. Inequality between sexes and within societies has a genetic proxy: inbalance between male and female ancestry-- find this with Star Cluster Analysis

    * Yamnayo are BIG in this.

    5. Ancient DNA is revealing TONS of surprises...

    6. Reich consistently points out places where he got stuff wrong or changed his mind

    * used to be strong proponent of Mitochondrial Eve hypothesis and Out of Africa Hypothesis

    * didn't believe Excoffier on lower fertility of Neanderthal-Human hybrids

    Highly recommended book!

    Some flaws that I'm not qualified to speculate overmuch on:

    Mainly, Reich is very dismissive of research outside genetics on the question of average phenotypic differences between groups as any kind of evidence for or against average genetic differences. I'm obviously not an expert on this, but head to Twitter to see smarter people duking it out on this or wait for more reviews from actual scientists...

    He also has a few throwaway suggestions on the moral imperative to treat individuals as individuals, and not let any conclusions we come to in the future on groups impact individual treatment. His suggestions are so uncontroversial and obvious (like his suggestion to measure phenotype instead of using genotype to predict phenotype) that I'm unsure if he meant them as serious suggestions as opposed to platitudes. For one, Stephen Pinker has made the same argument with the same reasoning in 'The Blank Slate' at least a decade before Reich, as have serious thinkers from all political sides for the last 50 years. So that's not exactly something we needed genetic evidence to remind us of. So don't expect political radicalism from this book-- which is a good thing, IMO.

  • Jayesh

    This was a fantastic condensation of modern research on genomics and it's effect on our understanding of anthropology and history. Really, what is it with biologists that they are able to write these books understandable to a relatively lay audience without hiding

    detail about how the scientists go about doing their research and draw conclusions:

    This was a fantastic condensation of modern research on genomics and it's effect on our understanding of anthropology and history. Really, what is it with biologists that they are able to write these books understandable to a relatively lay audience without hiding

    detail about how the scientists go about doing their research and draw conclusions:

    Not that some details

    hidden. Like use of Principal Component Analysis and other statistical techniques and how they get around problems with these techniques is mostly elided. Still it was fun learning about things Four Population Tests to identify likely common ancestors and how they group current and past populations of people.

    The weakest parts of the book are when Reich is trying to walk the tight rope of modern connections between race, behavior and genetics. Which is understandable, because it is a difficult topic. But his bad arguments don't do well for the values he wants to espouse. There is a lot of is vs. ought confusion, with no consistency. This is especially egregious in Chapter 11. Why do I need to be reminded of treating individuals as individuals, just because we find something about group averages. There's something to be said about Nietzsche, that he was correct to claim that trying to derive all our values from objective truth is not ideal, to say the least. But an interesting quote:

    Anyway the book is a lot of fun. One of the funniest parts was about them finding proof for West Eurasian ancestry of large parts of South Asian population:

    So to get around this:

    And for the rest of the chapter, he deadpan goes on using the ANI-ASI terminology.

    Finally, no one comes out looking good when you go far back in time. And we are mixes all the way down.

  • Biafra

    Due to Goodreads limits, this review is cropped. The full review can be found at

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    Due to Goodreads limits, this review is cropped. The full review can be found at

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    DNA vs Archeology

    Estimating the past from genomic data.

    Good illustration of why whole genome analysis can be very useful.

    Example of principal component analysis to reduce many genetic variations across groups into a single, easy to read graph.

    Text has many simple illustrations that help get scientific points across.

    Different statistics for admixture from

    . Reich could have included a paragraph or two on comparison between methods.

    =======

    Full review:

    .

  • Xenophon Hendrix

    The author, David Reich, is a eminent population geneticist whose work is shedding light on questions of archeology and history. This book is primarily about the origins and movements of the ancestors of persons today. When it sticks to that topic, the book is excellent, except for the occasional awkward sentence.

    Unfortunately, the author finds it necessary to make disparaging, and in my opinion misleading, remarks about Nicholas Wade, Henry Harpending, and James Watson. He also repeatedly attac

    The author, David Reich, is a eminent population geneticist whose work is shedding light on questions of archeology and history. This book is primarily about the origins and movements of the ancestors of persons today. When it sticks to that topic, the book is excellent, except for the occasional awkward sentence.

    Unfortunately, the author finds it necessary to make disparaging, and in my opinion misleading, remarks about Nicholas Wade, Henry Harpending, and James Watson. He also repeatedly attacks a straw man in regards to "racial purity."

    I recommend the book to those interested in population genetics, human biodiversity, archaeology, anthropology, and ancient history.

  • Peter Mcloughlin

    Traces the general history of humanity from its origins in Africa and the subsequent lineages that went to Europe, South Asia, East Asia, Australasia, The Americas and subsequent African lineages as they changed in the genetic record up to the present. Also covers the detective story behind the discoveries in DNA research which has given us a way more complete history than the archeological record. Tells the varied stories of humanity.

  • Mehrsa

    Such fascinating science and research on ancient DNA. I also really loved all the research about the Iranian Nomad populations that are basically the tribe that took over Europe because those are my people (kind of because there was a lot of mixing). It was also stunning to see how inequality and male domination affected genetics. Basically a few really powerful men who spread their DNA far and wide. Women obviously can't have too many children, but also history seems to be just conquering armie

    Such fascinating science and research on ancient DNA. I also really loved all the research about the Iranian Nomad populations that are basically the tribe that took over Europe because those are my people (kind of because there was a lot of mixing). It was also stunning to see how inequality and male domination affected genetics. Basically a few really powerful men who spread their DNA far and wide. Women obviously can't have too many children, but also history seems to be just conquering armies of men spreading their seeds over conquered populations of women.

    He also talks at the end about race differences and how we should be prepared to deal with what advanced DNA science will have to say about that. I think he's a bit more confident than his data can take him. I think the DNA stuff is obviously clear to him, but he's not an IQ scientist and I think most people who study cognitive testing believe that it is far from being scientifically rigorous or rooted in genetic differences. In other words, we haven't been able to separate genetics from environment when it comes to cognitive ability. Reich may be confident he can parse out modern races from their DNA, but I do worry about trying to plot races on cognitive factors. By all means, we should look at diseases and all sorts of stuff that have clear genetic variants, but before we start talking about intelligence, we better make sure the science on that is air tight.

  • Alison

    . This book has many very, very good qualities. It is, without doubt, the best modern summary of ancient genome research and how it is transforming our understanding of the past available. However, i

    . This book has many very, very good qualities. It is, without doubt, the best modern summary of ancient genome research and how it is transforming our understanding of the past available. However, it also carries some very deep, and dangerous, flaws. Reich is so keen to move us forward with new techniques that he tramples past cultural, sociological and anthropological scholarship that helps us to understand how we create narratives and guard against bias. In doing so, his book reinforces destructive ideas about race; human cognition and psychology and class and power. Perhaps ironically, in seeking to free us from antiquated scholarship, Reich plays straight back into dominant narratives that have explained - and justified - racial inequality for centuries.

    In many ways these are small flaws, affecting a few chapters at the end. But Reich has created a narrative around this in which he is a hero taking on the idiocy of political correctness, which makes it impossible not to treat this discussion as the center of the book. And as Reich says above, these newcomers to the field of human origins wield enormous influence, which brings with it responsibility for rounded scholarship.

    It has taken me a month to write this damn review (long time to have a tab open!) in part because Reich sets us such a trap for the critic: he consistently argues that those critiquing his view of race are motivated by trying to shut the discussion down. People like me are anti-evidence, and unless you are going to argue with him over the sequencing techniques, then the criticism is irrelevant. As it happens, I agree strongly, as do very many who think he is wrong, with the need to have evidence-based discussion about race, gender, intellect, cognition and human origins. Especially given the rise of overt racism, and the flock of racist men to blogs and discussion forums around genetic prehistory. So it has been important to me to ensure that it is clear that my objections are not to having a conversation, they are to his conclusions, and the way he has framed the debate, and most of all, what he overlooks.

    Now, Reich argues that he is countering racism: his book strips back the stupid claim that 'races' have existed for any significant fraction of human existence, and gives huge weight - as does all modern genetic work - to understanding that our ancestors mingled, migrated and procreated much more expansively than we had previously assumed. Our modern 'populations' have existed for not much more than 5000 years in most cases. (This itself shows what we mean - many populations actually have been relatively distinct for longer than that, the San, Australia's Aboriginal groups, Native Americans - but they don't correspond to our race ideas, which lump all Africans together, all Oceanic groups together etc - really, it is the inhabitants of Eurasia who have mingled incessantly, creating the populations who tend to hold social, economic and political power in our current world) Multiculturalism has been a consistent feature of human societies, and yes, conflict is as much a part of that condition as harmony: this is part of who we are, in all our glorious complexity. But the fact that Reich doesn't think he is making racist assumptions doesn't change two big errors: his argument that cognitive differences could exist between "large population groups" (i.e.: races) and his infuriating and frankly petulant dismissal of First Nations concerns around genetic research.

    On the first: to start, Reich is not in the majority in thinking that large populations are the most effective way to look at genetic difference - he himself outlines his differences with Svante Paabo in the book, although he talks down the support that remains for Paabo's view that clines is a more enlightening slice. He admirably starts by pointing out that race, as we think we understand, has been largely debunked. He attempts to distinguish himself from the rubbish spouted by journalist Nicholas Wade, and the prejudice of James Watson. But as the book progresses, he focuses increasingly on the possibility of differences which have evolved over the last 5000 years, providing markers between populations - despite the fact he presents no evidence for this. In the end, he seems to be warning that they might be right about some things, attacking his colleagues for using truisms like, there is more genetic variation within population groups than between them (this is, by the way, simply true) instead, presumably, of focusing on those differences which can be found. The fact that there is plenty of scholarship on those differences, such as skin colour, height and susceptibility to disease, doesn't count of course, because really what Reich is getting at is cognitive, personality and the "real" question of intelligence. Who is, after all, the most human? the fact we have little idea in any form of scholarship of what that actually means doesn't slow him down at all. And honestly, it should.

    On the IQ: look, there are many great articles on this already on the Interwebz. Start with

    . The issue here isn't that genetics doesn't predict the possibility of natural selection causing complex differences between populations (the only argument that Reich addresses in the book, and one which he says comes from political correctness, adding insult to disagreement); the issue is that the

    of modern society is that these differences do exist, when there is no untainted evidence for it. Mitchell in this link accepts the IQ test as a measure of intelligence - but many, many scientists do not. We have

    , in fact, that

    and

    : much of this research is centered on

    . This is why the one main significant study into IQ and genetics - which Reich makes much of - focused on a very uniform genetic population in a country with tiny economic and social inequality, and even then the implications of its results have been widely challenged.

    Reich's own research on earlier periods challenges the simple search genetics has for the unlocking nature of consciousness and humanity. He points out that despite large resources, there simply doesn't seem to be evidence that genetic adaptation closely precedes leaps in human development. This is not a surprise to evolutionary biologists, who have known for some time that our capacity to learn and create social structures which then shape our individual cognitive development is our strongest adaptation; that our closest primate relatives have genetic capacity for language and tool use, as well as often superior memory and recall. But the key lesson here: that we have an extreme ability to socially shape our children and hence create ourselves should also result in an understanding that we ourselves, us scientists, are also created and shaped by the societies that created us, is one Reich usually doesn't appreciate the impact of.

    In one rather infuriating section he comments that we should take the same approach to race as to gender, throwing out:

    This view, that gender inequality is just a bit of thorny issue society is working through, that most people accept that gendered differences in 'temperament' are 'profound' bears little resemblance to any serious scholarship on either gender, or neuroscience (which consistently finds less and less gendered differences), or for that matter the goddamn zeitgeist at the moment, and summarises Reich's dismissiveness.

    Reich at times shows flashes of insight into how social and biological factors interact: for example noting that genetic predictors in (again, uniform and highly equal society) educational rates may relate to differences in fertility, not cognition, or his wonderful aside that West Africans might not be faster, but just more genetically diverse than others, but when it hasn't been forcefully brought to his attention by a sociologist he met at a dinner party, he seems unaware that what he regards as common knowledge comes from a worldview based on relationships of power and social roles. In this context, his blithe assumption that we can find cognitive differences between populations - despite the complete lack of agreement into how to measure or understand cognition; and an awareness that our "common sense" assumptions are largely shaped by our social environment - is an infuriating result of isolating hard science from the social sciences and humanities.

    Nowhere is this lack of awareness that he has a worldview more evident than in his frustrated complaints about the role of First Nations peoples - particularly in the Americas - in refusing participation in genetic testing. Reich's bewilderment as to why this is even an issue is clear:

    and leads on to hints of wanting to disregard agreements with tribal councils not to proselytise around this research:

    Reich's claim that his research field has not done harm is a little naive. For starters, it involves his version of harm, which excludes the exploitation of genetic material for the primary gain of other groups. It assumes that his post-Enlightenment worldview - in which the search for information is noble, and never dangerous, and in which experimentation is more worthy than spiritual contemplation, is more worthy than differing worldviews which view knowledge without protection, context and responsibility as dangerous. It also ignores the attempts to patent genomic material in the 1990s, and the thirst for profit that US biomedicine is embroiled in, rarely to the benefit of participants. He lauds the work of researchers working with Aboriginal groups in Australia, without realising apparently that this work rests upon recognising that work with genetic material of Aboriginal groups must meet needs the community has identified. That is, it is about listening, respecting and offering resources: none of which is evident in Reich's approach to any of this.

    So, the good bits? Reich loves the pursuit of knowledge and it shows. And while he struggles so much with not recognising he has biases, he is refreshingly free from attaching his ego to particularly theories. He cheerfully admits where genetic research has proven his assumptions wrong, and this makes most of the book a page-turner, able to draw a reader in to rapidly shifting worlds of difference.

    Reich tackles a range of topics here: including the sensitive issue that the genetic evidence indicates we have more female ancestors than male. This process results from bottlenecks, or times where men fathered children on a wide range of women. While Reich clearly fears this will upset modern scholars, it is hardly a surprise to anthropologists well aware that polygynous child rearing is more common than polyandry, and that war and conflict are largely driven male invading forces. His research into the Indian caste system is fascinating, indicating the long-term effectiveness of social separation within an existing community, and providing really interesting takes on the interaction between social structures and genetic ones. The Brahmin caste, he argues, is far from purely different genetic stock, but bears markers of centuries of incestuous procreation and social isolation. I wanted far more on the Southern Route theory, and the role of Austronesian analysis - particularly given a month before the book came out, cave art was dated to 60,000 years in Northern Australia, which, if accurate, comes down solidly in favour of an early Southern route expansion (and Denosovan contact after arrival on the continent - or errors in genetic dating). Reich is well aware that this book is written at a moment in time, and it takes a certain courage to do that, as no doubt many of his current theories will be debunked in coming years. In being that brave, he's given the layperson a fabulous chance to explore a field in flux. It is just such a shame that he chose to mar this with an unsubstantiated argument about possible things people may find into the future, in a way which feeds into racism and sexism.

  • Gavin Leech

    Incredibly detailed and fresh, but also repetitive and indiscriminate. Had to think quite hard looking at some of the many diagrams showing e.g. hundreds of thousands of years of almost-noise recombination.

    Archeology has been transformed in the last decade, by the ancient DNA hunt. Reich allows us something precious, to see large and profound errors corrected, nearly as they are first discovered. But it just isn't that readable and the forest of details obscures even the giant new facts (Denisov

    Incredibly detailed and fresh, but also repetitive and indiscriminate. Had to think quite hard looking at some of the many diagrams showing e.g. hundreds of thousands of years of almost-noise recombination.

    Archeology has been transformed in the last decade, by the ancient DNA hunt. Reich allows us something precious, to see large and profound errors corrected, nearly as they are first discovered. But it just isn't that readable and the forest of details obscures even the giant new facts (Denisovan cross-breeding with us, Neanderthalian cross-breeding with us, very different pictures of paths of migration...)

  • Peter Tillman

    Go-to review is Biafra Ahananou's,

    "This book, even with its flaws, is worth reading for the great overview it gives into the emerging ancient DNA field that could have profound impacts on culture, politics, and science."

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