Inequality also leaves traces in the genome of ancient populations

When I was a boy, my house was full of history books that my father had bought, although unfortunately he never had the time to read them. Even the street that we lived on, in Barcelona’s Gothic Quarter, was steeped in history, as most of its buildings date back to the Middle Ages. Ancient history was rife with conquerors, dramatic quotes, bloody battles, and death. But the anonymous citizens, the common folk who make up the bulk of the population, were never mentioned. When the time came for me to choose a field of study, I opted for evolutionary biology, yet history has always interested me. (You could say, of course, that these two disciplines, along with astronomy, have one element in common: the temporal dimension.)

After years of working on Neanderthal genetics, I realized that novel DNA sequencing technologies could help us explore the recent human past, taking a new multidisciplinary approach that integrates genetics, archaeology, anthropology, and even linguistics. In 2014, I led the first effort to sequence the genome of a European hunter-gatherer using DNA extracted from an 8,000-year-old skeleton, and the following year we explored the genome of one of the first Mediterranean farmers.

During the following years, I continued this research working on projects through which I was able to examine different archaeological horizons, mainly in collaboration with David Reich, a Harvard researcher and pioneer in this field. In recent years we began to incorporate information from historical sources that sometimes challenged what we had known until then. A common conclusion of all these studies is that migration, and not just the spread of ideas, was a very frequent phenomenon in the past and that, in fact, modern human populations were formed by successive layers of different genomic ancestors linked to these migrations.

One day, in a casual conversation about my work, my wife told me that I was looking at the past from a male perspective and that the history of humanity (indeed, a long road peppered with suffering and discrimination, which has not ended for many) also included women, no less than half of the world’s population. And she was right: although women have been largely ignored in the ancient history books, they have given birth to each new generation of humanity. Think, for a moment, how differently a legend like the abduction of the Sabine women (and, by modern standards, subsequent rape) by Romulus and his companions in early Rome - abundantly represented in art in a rather heroic manner - would be told from the female perspective instead of the usual male one.

I realized that, directly or indirectly, new genetic studies were uncovering the many layers of inequality that existed in past societies, from the potential gender biases we discovered in these migrations to the social structures put in place to maintain those inequalities, while helping us find evidence in cemeteries linking wealth and social status to sex, kinship, and ancestry. Powerful men of the past may have had more offspring (by different women) than their contemporaries, whose fewer children were also less likely to survive.

George Washington’s dentures made with slave teeth

Thanks to some recent studies aimed at analyzing the genetic composition of African slaves, and others that studied the genome of modern mixed populations (especially those of the Americas), it was possible to reconstruct different reproductive patterns. Once again, if we change our point of view, certain anecdotes from the past, such as that George Washington’s dentures were made from teeth pulled from Black slaves, are more shocking, and it is logical that they have generated a wide variety of reactions.

It must be emphasized that all these patterns of inequality left genetic marks that we can detect in the genomes of ancient and modern human populations. Whenever I look at some new genetic study I discover new evidence of inequality and discrimination at different times. And there are many who suffered the consequences.

A number of puzzling ideas emerged from these observations. To name just a few: those who benefited from inequality in the past, resulting in more offspring, are more likely to be our genetic ancestors, and if wealthy men could mate with different women, and this was a common pattern, it is clear that women contributed more than men to modern human genetic diversity.

The philosopher Walter Benjamin was right when he said: “It is a more arduous task to honor the memory of anonymous beings than that of famous persons.” However, thanks to genetic data, it is now possible to achieve it. The first thing to say is that history – the history of heroics, wars, and conquest – has, in fact, been a history of inequality that shaped the genomes of humanity. That said, inequality is not just a curiosity of the past. I predicted that inequality would influence mortality caused by the Covid-19 pandemic in differentiated ways, and a few weeks later, my hunch was confirmed. Inequality is built into our genomes, but it also casts a long shadow over the future of society. We will have to decide, sooner rather than later, how we want to deal with it.

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