We are all Neanderthals too: There are no "pure" peoples, humanity is a mixed race

By: Simon Cooper / The Financial Times (headline: We are a bit Neanderthal)
Translation: Telegrafi.com

Through Lluís Quintana-Murci's window, fog obscures the Eiffel Tower. The Majorcan genetics researcher, long a permanent member of the Pasteur Institute, has not yet adapted to the gloom of Paris. He can rightly be called a migrant. his book, Human peoples, incorporating the last century's advances in genetics, explains that humans have always been migrants. "This is not forced socialization," he says. "It's science." And, the migrant people had relationships (“mixed,” as geneticists say) with other groups they encountered.

Genetics has advanced unimaginably since the 90s, when Quintana-Murci completed her Ph.D. The Human Genome Project, which sequenced the 3.2 billion nucleotides in our genome, was completed in 2003. Since the 10s, advances in the study of ancient DNA have allowed geneticists to compare prehistoric and modern genomes. Their findings are reconstructing our history. We can now map human migrations since Homo sapiens first left Africa, about 60 years ago. The past, says Quintana-Murci, is "the most natural experiment of all time", because it was carried out by nature itself. Genetic history helps us understand who we are.

An important discovery: Since Homo sapiens is a relatively new species, about 200 to 300 years old, humans are all genetically very similar. The world's eight billion people are much less different than our 200 chimpanzee cousins, Quintana-Murci writes. "The differences between the genomes of two randomly selected people, whatever their ethnic or geographic origin, are about three million nucleotides – in other words, 0.1 percent of the genome."

Few of these differences are ethnic. Senegalese individuals differ significantly from each other, but as a group they are very similar to people from Lille in France. On average, he writes, “85 percent of genetic variability is observed within a population; the rest is observed among them". Therefore, it makes little genetic sense to speak of "Africans" or "Europeans", considering that we all originated in Africa and have diverged very little genetically since then. Quintana-Murci says that mapping our genome moved us away from "a hermetic view of different populations, towards a view of a metapopulation made up of many different groups constantly exchanging genes."

Our sense of ethnic differences is accentuated by some obvious differences, most notably skin color. Humans adapted to different climates through natural selection. The darker skin helped protect against the hot African sun. In colder climates, where ultraviolet rays are scarce, which affects the production of vitamin D, lighter skin helps absorb them. But these differences are mostly superficial.

White and black people are not separate "races". "There are no 'pure' populations," says Quintana-Murci. "What are we? We are confused, just confused, all of us." The earliest documented admixture occurred "as soon as humans left Africa and met Neanderthals." (Just a decade ago, most scientists assumed we weren't related.) Today's Europeans, who all carry Neanderthal genes, are not "100 percent sapiens."

The greatest danger throughout our history, until we discovered vaccines and antibiotics, came from pathogens. Immigrants arriving in a new country encountered unfamiliar insects, while the natives had already adapted through natural selection. Only individuals whose immune systems could fight local pathogens survived and reproduced. So the fastest way to make children that could survive in that country was to mate with the natives.

What will happen in the human journey? Personalized drugs that target each individual's genome are still a long way from discovery, Quintana-Murci warns. One of the difficulties is that many genes affect the risk of developing a particular disease.

However, something else big is already changing: natural selection among humans is slowing. This is because today's vaccines and medicines allow almost everyone – in the wealthiest countries, regardless of their genes – to live to reproductive age. However, natural selection works in other ways. First it works much faster on microbes, which are adapting to survive our drugs and many of them are becoming resistant to antibiotics.

Meanwhile, in humans, natural selection now favors reproduction rather than mortality. In particular, male fertility is declining: sperm levels have halved in 40 years, possibly due to obesity, smoking and endocrine disruption from agricultural chemicals. More and more people reach reproductive age but do not reproduce. How can our genes alter these developments? The geneticist laughs: "Let's meet in 3000 years and see"! /Telegraph/