The poisoned inheritance of ancient genes

We will like it more or less, but it is unquestionable: physiologically we Spaniards are shorter and the Nordics are taller. The average height of OECD countries is 177 centimeters for men and 164 for women. In Spain we are somewhat lower: with 174 and 163, respectively. And although in recent decades the Iberian size has increased thanks to economic development and the improvement of socio-sanitary conditions, there is an immovable element against which we can do little: genes dictate how far our heads will end up separating from the ground. And specifically, the oldest genes we carry.

A recent study published by the magazine “Nature” has discovered in the DNA of 5,000 human remains from more than 30,000 years ago the keys to the physiological evolution of Europeans and, among them, the reasons for the differences in height or, more importantly, , of the propensity to suffer from diseases such as multiple sclerosis or Alzheimer’s.

Researchers from the Universities of Cambridge, Copenhagen and California Berkeley have created the largest ancient DNA bank in the world. By sequencing the genes of those individuals who lived in Europe and Asia millennia ago and comparing it with the DNA of current Europeans, they have been able to trace how those genes have been dispersed and how the information they have been distributed has been distributed. they carry on physiological characteristics or tendency to diseases. The results may provide answers to some European genetic peculiarities that, until now, were a mystery.

For example, it is known that the inhabitants of northern Europe make up the population with highest incidence of multiple sclerosis on the planet. The study has discovered that the genes that significantly increase the risk of suffering from this disease were introduced into communities in northern Europe 5,000 years ago through relationships with human groups of hunter-gatherers from the East.

In fact, the reconstruction work makes it possible to track how this genetic information has been distributed over time. The communities carrying these multiple sclerosis genes belonged to the so-called Yamna culture, settled more than 5,000 years ago in the Ponto steppe (between present-day Ukraine, Russia and Kazakhstan). Interestingly, the same genes that carry the susceptibility to multiple sclerosis confer protection against infections caused by contact with livestock. So these communities had a poisoned evolutionary advantage that they passed on to the northern Europeans with whom they hybridized. According to one of the study’s authors, Cambridge University professor Eske Willerslev, ““This finding may change our view of the origin of multiple sclerosis and how to treat it.”

Today there are twice as many cases of this disease in northern European countries than in southern countries. From a genetic point of view, the Yamna may be ancestors of northern Europeans and, therefore, the cause of this difference.

Intensive study of this impressive ancient gene bank has yielded other surprises. Among them, the reasons for the morphological variability between different communities of Europeans.

The European continent was populated by modern humans in three waves of migration. About 45,000 years ago, hunter-gatherers from Eurasia arrived in ancient Europe. Later, about 10,000 years before our era, a good number of settlers arrived from the Middle East and a third population contribution took place 5,000 years ago, in this case from the border between Eastern Europe and Asia. Anthropologists know that these migrations They generated genetic exchange between new relatives and archaic populations settled on the continent. But this exchange was not homogeneous: the difference in the dispersion of genes from one wave to another is responsible for the physiological differences between Northern and Southern Europeans.

For example, the inhabitants of Nordic countries are taller and have lighter skin than Mediterranean people because the former preserve more genetic ancestors among the shepherd families arriving from the Eurasian steppe.

But looks aren’t everything. Other genetic contributions have more impact on our lives than a few extra centimeters. In northeastern Europe, people today are at greater risk of diabetes and Alzheimer’s. Because? The study suggests that it is because they received more genes from the first migrations of hunters 45,000 years ago.

In the same way, it is known that we Europeans are the population with the lowest rate of lactose intolerant thanks to the fact that our genes came together with those of eastern agricultural societies adapted to the consumption of milk 10,000 years ago.

The new research opens a window to the study of genetic variability from an unprecedented perspective. Until now, it is clearly known that mutations in DNA cause biological changes that can shape a population’s ability to survive and adapt. But it is not yet well defined which of these changes sculpt the propensity to suffer from one disease or another: in other words, What genes that helped our ancestors survive today are a heavy burden that makes us victims of serious evils.

The work now published sheds some clues on the genetic dispersion of neurodegenerative and autoimmune diseases, on the origin of diseases such as autism and on the reason why some communities are more prone to depression than others.