Adam Rutherford: The Story Of Our DNA
‘May you live in interesting times’ says the apocryphal Chinese curse. I think a lot of us are longing to live in less interesting times, but so it goes. Brexit seems to have fueled a surge in the expression of race-related bigotry. The bewildering rise of Donald Trump appears to be having a similar effect.
The epic sprawling story of our species is punctuated by interesting times. I wrote A Brief History of Everyone Who Ever Lived because in the last few years DNA has been added to the pantheacon of evidence of our history, and many of these events are written into the code hiding in our cells. Our genomes themselves are rambling sagas, a disorganized logbook replete with tales of battles lost and won, of disease and famine, of sex and invasion, and of the migration of Homo sapiens from our nursery in Africa to every corner of the planet. We have just begun to understand how to sort this record, jumbled for eons by an evolution with no intention that it would ever be read. The first half of the book is really about the deep prehistory of our species, how we came to be what we are. The second is about who we are now, and what DNA tells us about ourselves.
Human genetics is a comparative science, which means we need to categorize and compare people. The worst manifestation of this very human characteristic has lead to some of the greatest divisions in our history, notably in the persecution of race. The history of genetics is part of that dark past too, and it was important for me to tell that story. Much of the science of studying people has Francis Galton as its intellectual forefather. He was Charles Darwin’s half-cousin, and a brilliant scientist himself. He invented a dizzying number of statistical techniques that we still use today; he drew the first weather map, conducted foundational work on the psychology of synesthesia, and designed a vented hat to help cool the head whilst thinking hard. He was also a hideous racist, a man convinced of his own genius, and of the dominance of white men over most of the people of the Earth. Galton formalized the idea of eugenics, for the improvement of the British ‘stock’, as was the contemporary parlance. We Brits talked about it a lot; Churchill and William Beveridge in Parliament were fans, as well as Marie Stopes, George Bernard Shaw and others in the social classes of influence. But unlike the USA and Sweden, we never enacted any eugenics policy. The grimmest realization of some of Galton’s ideas was the Holocaust and mass murders perpetrated by the Nazis.
The irony is that it was the development of Galton’s ideas into the study of genetics that has dispelled any sense that racism can be based in science. Contemporary human genetics has shown that there is no satisfactory overlap of how we talk about races, and how we can sort people using DNA. ‘Black’ is a virtually meaningless term with regards to dark skinned people, as Africans are more genetically diverse overall than the rest of the world put together. That means that a man from Uganda, and a man from Ethiopia are likely to more different from each other than they are to anyone else on Earth. The fact that there hasn’t been a white man in the Olympic 100m final since 1980 has been used to suggest that black people are biologically predisposed to be better at sprinting, possibly because they have more fast twitch muscle cells. Alas, knowing about the wealth of genetic diversity in Africa, this sentiment is rendered absurd. Any two sprinters in the Olympic finals are likely to be on average more different from each other than they are to a Dressage finalist. They are more likely to have similar genetics in the traits that are important for fast running though. Instead of lumping them together by skin colour, perhaps a better way of classifying these people would be as sprinters.
As with all science, advances in genetics have been facilitated by new and cheaper technology. We can now sample and read hundreds of thousands of genomes for a few hundred quid each. The first time, in the Human Genome Project, took hundreds of scientists 13 years and around $3 billion. And now, dozens of companies have sprung up that will read parts of your genome in exchange for some spit in a tube and the price of a Bruce Springsteen ticket. Some of them claim to tell you where your DNA ‘comes from’ in the deep past, though there is no known scientific method for doing that. What they are actually doing is telling you where you DNA is shared on Earth today. It’s big business nevertheless, because everyone wants to discover they have Viking ancestry or someone similarly awesome.
I can do it for free. We only have to go back around 600 years to find a single common ancestor to all Europeans, such is the reality of our family trees – not arboreal at all, but tangled thickets that fold in on themselves many times over. A thousand years ago, something truly weird happens. Everyone alive in Europe in the 10th century who has descendants alive today is in fact the ancestor of every European alive today. The branches of our family trees cross through everyone a thousand years ago. What this means practically is that every European has Viking ancestors, and Saracen ancestors, and Jewish, Goth, Norman, Saxon, and every conceivable European people and beyond as their ancestors. Extend this principle out to the rest of the world and the date of common ancestors of everyone alive on Earth today is only around 1400BCE. We are all mongrels. Humans are too mobile and too horny to stay put geographically or genetically.
The genome is a grand poem, a saga of our pasts. We’ve just begun to read it, but just as important as what it can tell is what it can’t. Recently it has emerged that some racists are claiming that their results from commercial genetic genealogy testing companies are proving their racial purity. As so often is the case with people unencumbered by facts, precisely the opposite is true. Racism persists, but at least we can say with certainty that it cannot be justified using genetics.