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The Invisible History of the Human Race
How DNA and History Shape Our Identities and Our Futures
Of Christine Kenneally's father's father - a man neither Kenneally nor her father ever knew, a man who did the deed requisite to reproduction and promptly vanished - she asks, - Did he leave anything more significant than the loud bang of a door shut down the generations?- Of course he did. He left his DNA and a granddaughter determined to draw from modern genetics and hard-won family history a coherent account of her roots.
Kenneally’s own heritage is only one of the mysteries she pursues in The Invisible History of the Human Race, a smart, splendid, highly entertaining look at how DNA, increasingly visible to us since we first sequenced the human genome in 2000, can open up tracts of human history that had been entirely obscure.
While DNA may now be visible, however, it remains more hint than history. Kenneally, a journalist and linguist, shows that just as a gene usually delivers its genetic message only in conversation with an incoming chemical messenger, so our DNA tells its tales most fully only in light of the history of the people who carry and interrogate it. It takes all those threads to get the whole story. And Kenneally wants it all.
“If everyone had his DNA analyzed,” she writes, “and that information were linked to everyone’s historical information, it would be the nearest thing to the book of humanity.” She backs up this claim beautifully, showing how genetic analysis can be combined with skillful mining of historical, social and cultural information to solve fascinating riddles of ancestry.
The book would stand strong on its weird factoids alone. For instance: In Europe, the inheritance of surnames became common in the last 200 to 900 years, depending on country and culture, which makes it difficult to trace a family tree back beyond about 1500. Also: The rarer a surname, the more likely two men bearing it are related. Thus 87 percent of the few men named Attenborough descend from a single, distant forefather. (No wonder Richard and David are brothers.) Possibly my favorite: Sex cuts and reshuffles our genomes so sloppily that much DNA gets lost through the generations, like dropped playing cards. You have many distant ancestors from whom you received very little or even no DNA.
Despite such wonders of ancestral science, Kenneally finds that many people consider genealogy silly. A scholar prominent a century ago opined that people who charted their family trees did so out of 'snobbishness and vanity.' In 2007, one science writer warned his genealogy-obsessed daughter that 'nothing in her genealogy defines her.'
'Really?' Kenneally replies. 'If a person's genealogy is the series of individuals whose coupling eventually produced that person, then it's hard to see how this assertion is plausible.'
For many, unease with genealogy stems from its exploitation by eugenicists. In Nazi Germany, for instance, one’s family tree, embedded in official identification papers, became literally a matter of life and death. Eugenicists have rationalized some of history's most heinous acts with the science of ancestry. But eugenics, Kenneally reminds us, was born as and remains a distortion of science. Its founders and champions were elites who took inherent differences as a given -and themselves as humanity's highest form. The problem was not the theories but 'the way they were used to give longstanding social divisions a scientific rationale.'
In America, discomfort with genealogy is sharpened by our inspiring delusion that one can live free of history - as Willie Nelson sings, 'It's nobody’s business where you're going or where you come from, and you're judged by the look in your eye.' At its extreme, Kenneally writes, this 'reflex against the idea that the past must have meaning . . . became a belief that the past has no meaning.'
Yet the past's value and meaning are rendered powerfully clear in Kenneally's stories of people whose pasts were erased by history: African-Americans, Jews, orphans. Genetic analyses and genealogical databases like those at Ancestry.com and Family Tree DNA, especially when combined with earnest exploration in archives, now enable people to reconstruct lost lineages. Far more often than not, their reconnection with both family and history changes and deepens their lives. Other sleuthings examine broader puzzles: One chapter describes a fascinating study in which maps of genetic differences within the British Isles neatly match cultural and linguistic distinctions.
Perhaps the book's most resounding sections are those showing how culture, rather than genetics, can shape lasting differences in human values and behavior.
Kenneally describes a study by the economists Nico Voigtländer and Hans-Joachim Voth, which found persistent differences in anti-Semitism among towns in Germany. Communities that reacted to the Black Death some 600 years ago by blaming and massacring Jews were far more likely to lead pogroms against Jews in the 1920s and to turn Jews over to the Nazis in the 1930s and '40s.
In a separate series of studies, the economists Nathan Nunn of Harvard and Leonard Wantchekon of Princeton found a similar cultural legacy that shaped trust - a trait some presume to vary according to genetic makeup. Nunn and Wantchekon noticed that the poorest regions of Africa were the regions most exploited by slave traders in the 18th and 19th centuries. These areas suffered decades of raiding in which any stranger might prove a kidnapper, and in which slavers often gained access to their victims by bribing or blackmailing relatives or village authorities.
Clearly such behaviors may have eroded trust at the time, but could the effect last? Nunn and Wantchekon found that it does. The more a population was exposed to slave raiding generations ago, the lower its measures of trust and economic activity today. The specter of slavery, they concluded, had done long-term damage to the social bonds necessary for efficient trade. The economies and people continue to suffer accordingly.
It's a far more plausible and evidence-based explanation for Africa's economic troubles than the one offered by Nicholas Wade's recent book, 'A Troublesome Inheritance,' which, with vaporous evidence, attributes weak African economies to African-specific genetic profiles that purportedly discourage trust. Genetics gives all humans the power to create culture. Yet it appears most likely that it is not genetics but culture's manifestations, some lovely, some horrific, that distinguish and divide us.
Alas, even these fancy new tools can't crack every mystery. Kenneally doesn't find her missing grandfather, but she does discover further up her father's family tree a convict - one Michael Deegan, her great-great-grandfather, who in the mid-1800s was shipped from Ireland to Australia with a boatload of criminals for stealing a handkerchief. Her father absorbed this news far better than he did his father's haunting absence, confirming Kenneally's belief that people who excavate their pasts are almost always glad they did. It's easier to embrace a thief than a phantom.
Given how fast genealogy is advancing, Kenneally may find her missing grandfather yet. Given how fast genetics is advancing, parts of her book may need updating even as the ink dries. But what will prove lasting is her evocation of how much perspective and even wisdom can be extracted from some determined digging and a bit of spit. The breadth of this book; its abundance of enthralling accounts and astonishing science; its adept, vivid writing; and Kenneally's exquisitely calibrated judgment make it the richest, freshest, most fun book on genetics in some time.
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