Human women preferred Neanderthal men. This solves a major DNA mystery

Scientists have known for years that homo sapiens carry Neanderthal DNA, but not a lot of it. Some humans do not have any of their genes. They have now found the reason behind it. According to a study, the intermingling and mating happened in one very specific pattern - Neanderthal men and human women were the ones who established physical relations. There is a time period when both species lived together. During this time, home sapien women apparently preferred the short and stout Neanderthal men. For 20 years, experts have talked about "Neanderthal deserts," or places in the modern-human genome where Neanderthal genes are rare. They have proposed several reasons for this. One of them is that the Neanderthal DNA was toxic and was removed by natural selection. The two groups interbred a few times, but the genes we inherited from Neanderthals are present only in tiny patches on our X chromosome. This has stumped scientists for years.

The mystery of the X chromosome

Ancestors of the two groups went their separate ways 600,000 years ago. Today, most non-African people carry an average of 2 per cent Neanderthal DNA, while a few groups in Africa have up to 1.5 per cent. But they inherited the genes from Homo sapiens, who mixed with Neanderthals in Eurasia and then moved to Africa. The genes from the now-extinct species can be found in greater numbers across our other chromosomes, but not on X. In fact, there are regions on the X chromosome where no living humans have any Neanderthal ancestry. Alexander Platt, a population geneticist at the University of Pennsylvania, said in a statement, that the belief has been that their genes were biologically "toxic" to humans and caused health issues. So they were purged with evolution.

In a study published on Thursday (February 26) in the journal Science, researchers concluded that "Neanderthal deserts" actually happened because of mate preference. They analysed the genomes of 73 women from three modern-day African populations with no Neanderthal ancestry, and compared them with those of a few Neanderthals. The latter's X chromosomes had significantly higher amounts of modern-human DNA, which they say is because of how they mated. If female homo sapiens mated with male Neanderthals, it would lead to fewer Neanderthal X chromosomes entering the human gene pool. Previous studies showed that male Homo sapiens and female Neanderthals were mating. But clearly, they were wrong.