Book Review: Who We Are and How We Got Here


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. Goodreads review at

This review will likely be updated as I mull over or re-read the book.

[…] when we discover biological differences governing behavior, they may not be working in the way we naively assume. — David Reich, Who We Are and How We Got Here.

Reich has done a tremendous job condensing the work of many people and disparate areas of research into a compelling story that is potentially more informative for the history and process behind the scientific discoveries than the conclusions or his commentary on their societal effects. While the book is highly recommended based alone on the wealth of new ideas and potential to upturn old facts accepted by many, and is the reason I gave it a high rating rather than because I agree with everything said, it should be read with caution and an eye for "what is not said" for reasons pointed out below.

DNA vs Archeology

The book is mainly divided into an introductory portion, where the story of the Neanderthals helps provide a basis to go over techniques used in the ancient DNA field. Reich then moves across the globe—from Europe through India, the Americas, East Asians, and Africa—and goes over different migratory patterns that have been revealed by ancient DNA analysis. In addition, as is the case with India, he shows cases where endogamy (marrying within certain groups) can be demonstrated by analysis of highly unlikely similarity of DNA coding regions across time in specific populations. Further, he also shows how cases like the "Star Cluster" can help demonstrate cases in which specific males (or groups of males) had an outsized levels of breeding success, potentially due to war or migration as mentioned previously. An interesting question that he does not really address is the use of ancient DNA analysis to show how monogamy or polygamy play out in actuality, or if there was more cheating going on than would be expected giving stated societal norms across time and regions. Lastly, he ends looking both at the future (good) and the ethical implications of ancient DNA analysis (the weakest part of the book, more on that later). Overall, the style suites the topic really well and is a great way to get people new to the field acquainted with a forest-level view.

Reich does a convincing job of showing the advantages of ancient DNA analysis over traditional archeology in certain areas, such as pointing out the discrepancy between archeologists claiming that for there to have been a large incursion of non-Indians into that subcontinent, replacing people and leaving a genetic footprint, that there would be carbon, etc. evidence of burnt towns, etc. But the well recorded fall of Rome by the Visigoths and others did not leave such a record to the degree anticipated, throwing such conclusions into doubt. This can be captured in the classic phrase "absence of evidence is not the evidence of absence".

Estimating the past from genomic data.

However, and this is a theme about my criticisms of the book, he does not provide examples or speculate on places where the archeological record does show migration or invasion but there is not much ancient or modern DNA evidence left. Two scenarios (of many) would be an invasion where the invading population did not breed much with the locals despite large changes to civilization (think modern American wars) or pass through migrations on the way to some other destination (if those occurred). It would have been informative for him to spend time on the limits of what could possibly be known given ancient DNA basically relies on the dynamics of sex to have occurred in some predicted pattern (e.g. conquering males impregnating conquered females). Further, it is not clear how much the Star Cluster or similar traits is due to a single male or many closely related males, e.g. whether there is a limitation in what this type of analysis can tell us. These might be hidden within academic reviews, but the point of this book should be to give a high-level view of the pros and cons of ancient DNA analysis without a reader needing to get their hands dirty on the first pass.

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

On the other hand, he does a good job pointing out several neat ideas, such as due to the random splitting of DNA during production of gametes, that several generations back one is unlikely to contain DNA from all ones ancestors (by sexual reproduction). In addition, he does a good job at attacking old dogmas that are based on bad assumptions, such as Richard Lewontin's 1972 study The Apportionment of Human Diversity (see Lewontin's Fallacy, that don't take into account the whole genome or correlations between variations across the genome. This type of thinking is still prevalent, as can be seen in a recent National Geographic issue, see There’s No Scientific Basis for Race—It's a Made-Up Label.

In addition, his small aside about finding that the cochlear contains the best store of ancient DNA is fun and could potentially have been an opportunity to point out serendipity in science (should that be the case here). There are several other times, such as the story of discovering "ghost" populations that may no longer exists but related Europeans and Native Americans that was resolved finding the Mal'ta boy, where he brings up cool stories of how science leads to hypotheses turns to field work and final novel insights about the world. This is captured in a nice assertion Reich makes near the beginning:

We scientists are conditioned by the system of research funding to justify what we do in terms of practical application to health or technology. But shouldn’t intrinsic curiosity be valued for itself? Shouldn’t fundamental inquiry into who we are be the pinnacle of what we as a species hope to achieve? Isn’t an attribute of an enlightened society that it values intellectual activity that may not have immediate economic or other practical impact? The study of the human past—as of art, music, literature, or cosmology—is vital because it makes us aware of aspects of our common condition that are profoundly important and that we heretofore never imagined. — David Reich, Who We Are and How We Got Here.

And it reminds me of Richard Feynman's excellent The Value of Science essay and a key quote:

Another value of science is the fun called intellectual enjoyment which some people get from reading and learning and thinking about it, and which others get from working in it. This is an important point, one which is not considered enough by those who tell us it is our social responsibility to reflect on the impact of science on society. — Richard Feynman The Value of Science.

Reich also gives overviews of several techniques used in the field to identify likely common ancestors (Four Population Test) and to group current and past groups of people (e.g. principal component analysis). These are supplemented by excellent diagrams. However, he doesn't spend much time pointing out to the reader problems with these techniques or how they get around them. This is especially important as it relates to discussions of grouping people into categories based on (in the book) obvious delineations between say Europeans and some Asians subcategories.

Our initial approach was to carry out a principal component analysis, which can identify combinations of mutation frequencies that are most efficient at finding differences among samples. — David Reich, Who We Are and How We Got Here.

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

As a scientist, and knowing how quickly new fields can evolve and old methods be found to contain technical and conceptual errors, I am alarmed by Reich's lack of giving any kind of confidence (mathematical or otherwise) about statements being made that upturn old archeological or other theories. Given many studies he cited are less than a decade, sometimes only a couple years old, this is concerning. He does not spend much time going over more caveats to the technical methods (e.g. extraction of DNA from ancient samples, though he does talk about some initial challenges and solutions in the case of Neanderthal DNA) or conceptual ideas (e.g. Four Population Test). This is evidenced, for example, in his out of place bringing up of the Jefferson-Hemings relationship that adds nothing to the story but he presents as if it has been conclusively shown (with genetics, while glossing over the caveats). More humility about the possibilities of ancient DNA analysis would have strengthened the book.

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

Reich would also have done well to specifically state who he is referring to when he makes comments about those wanting to return to a 'racially pure' state, while he leaves their timescale for determining purity indefinite. Those discussing maintaining a recent European stock in their writings (e.g. The Daily Stormer, American Renaissance, Occidental Dissent, etc.) are slightly different that those proposing old Nordic Theories and similar stories (e.g. see The Long Journey, The Rising Tide of Color: Against White World Supremacy, etc.). He does briefly mention the Eurogenes and several other blogs, but only in passing and not directly in relation to his reference to 'racists' and 'bigots'. Further, he then contradicts himself by pointing out:

However, in Europe, where we have made most progress in the ancient DNA revolution so far, we know that by four thousand years ago, many populations were already highly similar in their ancestry composition to those of today. […] For example, the classic measure of genetic differentiation between two British populations is about one hundred times smaller than the same measurement of population differentiation comparing Europeans to East Asians. — David Reich, Who We Are and How We Got Here.

That he does not attempt to reconcile these comments about populations that are relatively homogenous and have not mixed much over recent history leaves room for people to misinterpret or use such findings to justify their beliefs.

Ancient DNA has established major migration and mixture between highly divergent populations as a key force shaping human prehistory, and ideologies that seek a return to a mythical purity are flying in the face of hard science. — David Reich, Who We Are and How We Got Here.

In addition, at the end of several chapters and throughout the book Reich makes reference to 'racial purity' not being a thing—without taking care to note that purity depends on the timescale used and, thus, is an annoying strawman. As noted above, he also contradicts this statement in several cases, among which include the distinct ethnic groups in Indian that have been maintained for tens of generations even among physically mixed populations.

Around a third of Indian groups experienced population bottlenecks as strong or stronger than the ones that occurred among Finns or Ashkenazi Jews. […]Many of the population bottlenecks in India were also exceedingly old. […] It meant that after the population bottleneck, the ancestors of the Vysya had maintained strict endogamy, allowing essentially no genetic mixing into their group for thousands of years. Even an average rate of influx into the Vysya of as little as 1 percent per generation would have erased the genetic signal of a population bottleneck. The ancestors of the Vysya did not live in geographic isolation.[…] And the Vysya were not unique. A third of the groups we analyzed gave similar signals, implying thousands of groups in India like this. — David Reich, Who We Are and How We Got Here.

In addition, he also seems focused on the idea of human migrations to the exclusion of focusing on how ancient DNA can tell us about changes occurring in non-migratory populations (thought he hints at the end of the book about this). For example, this could address Clark's A Farewell to Alms assertion about rich Britons breeding more being a reason for the industrial revolution and would be a starting point for many interesting analyses. During the discussion of the low occurrence of mixture between physically inter-mixed groups within India, e.g. endogamy or the caste system, he then goes on a tangent about his Jewishness and how he sympathized with the (unnamed) people who were prevent from finding love outside their ethnic/social group. These very overt tendencies to favor mixture over non-mixture are concerning in that he doesn't state in reality what guides his (and those in the fields) scientific questions and how that might bias future hypotheses or research, impacting interpretation of the past and having consequences for how society at large interprets the fields results.

The genome revolution provides us with a shared history that, if we pay proper attention, should give us an alternative to the evils of racism and nationalism, and make us realize that we are all entitled equally to our human heritage. [emphasis mine] — David Reich, Who We Are and How We Got Here.

This book, along with the excellent The Neuroscience of Intelligence by Richard Haier and many others will start to raise questions that need to be addressed by scientists and non-scientists. To put it bluntly, old and new research points toward the ability to quantify intelligence (broadly defined or by IQ) and DNA (and other) analysis has shown fairly definitively that there are different clusters of humans (e.g. ethnicities and ancestral groups for those wanting to avoid the loaded 'race' category). The question remains that once people combine the two areas of research, as China is attempting to do specifically looking at the genetics of g, are we as a society equipped to handle the results regardless of what they might be (especially if differences appear)? Will nationalism of the kind focused on celebrating a shared culture be instead directed toward war-like nationalism focused on extermination of those with traits that are not desired (by some group)? His blanket negative statements on anything tribal related—be that racism, nationalism, endogamy, etc.—cloud useful insights and suggestions that could be gleaned by a more nuanced position.

Different statistics for admixture from Schaefer, 2016. Reich could have included a paragraph or two on comparison between methods.

In an individualistic society, ethnic history reminds us of the enduring consequences of centuries-old cultural patterns into which each individual is born. […] It is not personal merit but simply good fortune to be born into a group whose values and skills make life easier to cope with.[…]Substantial reshuffling of the rankings of nations and races at different stages of history undermine genetic explanations in general. A reshuffling of the IQ rankings of American ethnic groups within a period of half a century26 undermines the theory of genetic determination of intelligence, even aside from questions about the tests themselves. The fact that black orphans raised by white families have IQs at or above the national average27 is even stronger evidence against that theory. — Thomas Sowell, Ethnic America.

Thomas Sowell in Ethnic America appears to attribute many of the differences between ethnic groups to differences in culture and notes that persistent disparities between African-Americans/Hispanics and Caucasian-descent/Asians need to be explained. In his famous How Much Can We Boost IQ and Scholastic Achievement? and subsequent essays and books, Arthur Jensen proposes that IQ is heritable. The Bell Curve, Levin's thought-provoking Why Race Matters, and many others point toward potential genetic differences between groups. Reich somewhat addresses this field of research but does so haphazardly and at times commits the same errors as he accuses other of, e.g. when criticizing Watson and others, he notes that there is no genetic evidence of different IQ of (sub-Saharan) Africans, ignoring the evidence that there is a lower IQ (but that we don't yet know the genetic origin). He offers the following solution to deal with the fallout of finding differences between human groups:

The right way to deal with the inevitable discovery of substantial differences across populations is to realize that their existence should not affect the way we conduct ourselves. As a society we should commit to according everyone equal rights despite the differences that exist among individuals. If we aspire to treat all individuals with respect regardless of the extraordinary differences that exist among individuals within a population, it should not be so much more of an effort to accommodate the smaller but still significant average differences across populations. — David Reich, Who We Are and How We Got Here.

Given human nature toward tribalism and noticing differences, this is a naïve solution. It would have been nice for him to at least briefly note how this type of thinking jives with how humans behave in the real, non-utopian world. Seeing as he makes mention of the misuse of archeology in the past by National Socialists and others, this is not too much to ask. There are many other gaps along these lines that he should have addressed, but instead danced around or ignored.

As noted, mixture is a constant theme throughout the novel (the first figure is "30 Population Mixtures"). Further, his support/advocacy of mixture ("Mixing is in human nature, and no one population is—or could be—“pure.”") and that everyone should be treated the same ignores a key point: if you want your society to have X characteristic then it may no longer have X characteristic if the genetic composition changes. This is an argument for not treating individuals the same, since they carry with them genes that have societal impacts (and regression to the mean means that individuals who deviate from an ethnic/ancestral trait may more likely lead to offspring with said trait than those from a different population). That he completely ignores this obvious argument should give one pause.

He also continually rests on this nature fallacy, e.g. the idea that because mixture happened in the past, and it is to be noted with a population of different genetic stock and abilities, that it would be beneficial to do so today. This is erroneous. For example, this would assume that replacing relatively ethnically homogenous Japan (regardless of whether they are formed from a mixture of populations thousands of years ago) now with a largely mixed population, from say Europe or sub-Saharan Africa, wouldn't cause large cultural, political, and other changes. If one desires Japanese culture as it is now, then they would not want mixing. Is this wrong? That nuance isn't taken up in the final part. Dealing with this more honestly would have improved the text rather than having him continually beat a one-sided drum.

Analysis of population sizes via ancient DNA is very interesting and Reich does a good job indicating why Y chromosome vs. mitochondrial would give different estimates.

Once past the ethical chapters, the last one ("The Future of Ancient DNA") is rather good and his hinting that we can also use ancient DNA to analyze non-human genomes that are relevant to disease, diet, and other aspects of human behavior and civilization is exciting. It would have been great for him to briefly go into any discoveries in these areas (e.g. see Ancient human microbiomes). Alas, this leave room for the reader to follow-up themselves (or wait a decade for a sequel that includes these discoveries). This is particularly true when he notes the likely specialization that would occur within the field; I imagine great archeological texts like Architecture of First Societies: A Global Perspective would benefit from ancient DNA insights along with ancient DNA researchers clarity of thought would be improved by importing new ideas from archelogy (e.g. saying "first societies" leads to hypotheses that are excluded by calling people "hunter-gathers").

In the end, this book is worth reading because it will make one think and is told in an "adventures of science" style that is captivating and informative. The flaws in his statements outside his area of study—especially dealing with mixture, IQ/behavior differences, and policy solutions to the coming genetic discovery wave—do give one pause as to what aspects within his own field he is leaving out due to his stated and unstated biases. However, as an overview of the field and a jumping off point for future study and discussion, this is highly recommended.

p.s. Letters such as How Not To Talk About Race And Genetics that put forth arguments like "Human beings are 99.5% genetically identical.", among others, as reasons why ethnic, racial, or whatever term you want to use to distinguish groups of humans with varying genetic and physiological composition, do not exist are not helpful. For example, small changes/differences can have large non-linear effects in complex systems like the body (see the classic case of Cystic fibrosis). This is in addition to odd, flawed arguments such as because sickle-cell is associated with "blacks" but occurs in other populations, that "black" is not a proper categorical label, ignoring whether that is the true bases for lumping (West) African together rather than a constellation of traits. All of this without providing sources for their claims. Reich addresses some of these points within his book and specifically makes the note that ancestry (e.g. more precise terms) can be used and bluntly points out that there are distinct groups of humans based on genetic data (other sources can be used for other anatomical, etc. data that he doesn't go into). Confusing the truth through sophistry is not a good long term strategy.

Other worthwhile reviews:

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