Now the science ‘guilt’ to the origin of livestock

For a long time it has been a suspicion, a logical hypothesis but difficult to prove: that our decision to Domesticate animals and live with them unleashed the great pests that have ravaged humanity. Now, the biggest study of ancient DNA of pathogens ever has confirmed it.

An thorough analysis. Analyzing 1,313 human remains of up to 37,000 years old, a team from the University of Copenhagen has created a genetic map of diseases and has found the exact moment in which everything changed: about 6,500 years ago, with the arrival of livestock.

A 37,000 years map. The study, published in the prestigious Nature MagazineIt is not a simple confirmation. It is a time trip at the molecular level that draws 37,000 years of the silent struggle between humans and pathogens in Eurasia. The results in this case demonstrates that the change to an agricultural and livestock lifestyle was the entrance door for the Zoonotic diseasesthose transmitted from animals to humans, which drastically increased the burden of morbidity and molded our history and our own genetics.

How they did. To achieve this feat, the scientists analyzed sequencing data of 1,313 old individuals, covering from the upper Paleolithic to historical times. In their teeth and bones they found the genetic footprints of a true catalog of horrors of the past.

What diseases they found. After performing this molecular analysis, they were able to determine the presence of several diseases that now heard them can enter normal, but the same did not happen at that time. To understand them better, they can be summarized as follows:

• Bubonic plague (andErsinia Pestis): They identified 42 cases, 35 of them completely new, greatly expanding the map of the plague in ancient times.
• Lepros (Mycobacterium leprae): It was detected in seven individuals in Scandinavia, appearing from the Iron Age, which supports the theory that the trade of squirrel skins could facilitate its transmission.
• Recurring fever (Borrelia recurrentis): A disease transmitted by lice with high mortality. The study points to 34 new cases, demonstrating that it was a much more common plague than was thought.
• Hepatitis B: 28 cases were found, confirming their presence for millennia.
• Malaria: nine infections located in three different species of Plasmodium, with the oldest case dated in the individual of the Bronze Age in Central Europe.

The moment in which everything changed. The most resounding conclusion of the study is that although the human being has always lived with pathogens, those of Zoonotic origin They are not detected until about 6,500 years ago. Its appearance coincides with the generalized domestication of livestock and the beginning of large -scale agriculture. The peak of these new diseases was reached about 5,000 years ago, a period that coincides with the great migrations of the pastors of the Euroasy steppe, who, together with their herds, could have acted as transmission vectors throughout the continent.

Why not before. “It is a beautiful idea that makes sense: livestock brought zoonotic diseases. But there really is very few overwhelming tests about it,” Martin Sikora saidauthor of the study.

Until now, the evidence was scarce because most infections do not leave visible marks in the bones. But as they point out in the study, examining a large number of pathogens and looking for some temporal trend that will support that hypothesis has managed to find the necessary evidence.

Older plague cases. The team has identified the presence of Y. Pestis In three individuals between 5,700 and 5,300 years ago, located in western Russia, Central Asia and Lake Baikal. This finding pulverizes the previous record (a woman in Sweden from 5,000 years ago, also discovered by them) and defies the idea that the first plague outbreaks were isolated events.

An millenary coinfection. A hunter-gatherer who lived in Russia 11,300 years ago showed evidence of a double infection in his body: diphtheria (C. Diphtheriae) and Helicobacter pylori. This is a fairly unusual combination that demonstrates how complex the world of diseases is, even before agriculture.

We are the children of the Neolithic (and its pests). For Carles Lalueza-Fox, geneticist of the Institute of Evolutionary Biology of Barcelona, ​​this work is a fundamental step to understand the pandemics not only as tragedies, but as “engines of social and political change” and factors that have modeled our genomes.

In this way, the study provides the direct evidence that was missing for one of the most important transitions in human history. The Neolithic Revolution not only brought us agriculture, villages and eventually, cities; It also inaugurated a new era of diseases.

Images | Stijn Te Strake National Institute of Allergy

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