Prehistoric Europeans drank animal milk millennia before they could digest it

For hundreds of thousands of years, adult humans could not digest milk.

His body did not metabolize it correctly as it did not have an enzyme (lactase), which allows it to absorb lactose, the main carbohydrate of dairy origin.

However, a few millennia ago (the exact time varies by region) Europeans began to consume dairy products.

A genetic mutation allowing lactase persistence after weaning also occurred.

Science considered these two processes as one of the greatest examples of evolutionary convergence: the consumption of a liquid with so many nutrients was an advantage if you had the ability to assimilate it.

Now, one of the largest studies to date shows that there was no such convergence.

The job,

During their evolution, hominids, but also the rest of the mammals for which information is available, lost the ability to produce lactase after weaning.

For nature, it would seem the best solution to favor the survival of the species, with some children leaving their place for the next generation.

In one of the basic features of the Neolithic, humans corrected natural designs.

The domestication of various animals must have been first for their meat.

But as many sites show, little by little the consumption of milk was introduced.

The first evidence of its consumption has been found in Anatolia (Turkey) more than 9,000 years ago.

This was one of the foci of arrival of the Neolithic culture, with its sedentarization, agriculture and livestock, to Europe.

And already about 6,000 years ago,

More than a hundred researchers have drawn up a kind of milk map of Europe.

Led by Professor Richard Evershed of the University of Bristol, they compiled a database of nearly 7,000 traces of animal fat detected in thousands of pottery shards from 554 sites in Anatolia, the Middle East and Europe.

Published today in the scientific journal

, the map shows how dairy products spread at the rate set by the expansion of the Neolithic culture itself.

Although there were setbacks and areas where the intake disappeared at one point only to reappear centuries later, the current seems clear: it reached Europe through the southern Mediterranean, with a subsequent expansion through the Atlantic fringe of the European continent, already reaching some 3,000 years ago at the Nordic regions.

The excavator Yuliet Quintino shows one of the ceramic fragments.

Its analysis with gas chromatography coupled to a mass spectrometer allows the presence and type of organic residues to be detected.Cristina Valdiosera

One of the points on that map is El Portalón de Cueva Mayor, in the Sierra de Atapuerca (Burgos).

There, the study of hundreds of ceramic fragments in whose pores tiny amounts of fatty acids were trapped has helped to know what prehistoric people ate and drank.

Eneko Iriarte, from the Human Evolution Laboratory at the University of Burgos and co-author of the

study , highlights the temporal amplitude of the El Portalón site.

“Milk consumption dates back to the Neolithic, about 7,400 years ago, and over time, the quantity and variety of dairy products are increasing,” he says.

However, El Portalón also helps dismantle the theory that milk consumption and lactase persistence went hand in hand.

In 2014, a study of the DNA of 18 Neolithic individuals found at this site showed that none had the genetic variation (allele) that allows the production of the enzyme beyond childhood.

In fact, the present research published in

has analyzed the ancient DNA of 1,786 prehistoric humans from Asia and Europe to trace the emergence and trajectory of the new allele.

"At the beginning of the Neolithic, everyone was intolerant," recalls Iriarte.

The projection of lactase persistence follows a graph in the form of a capital S (known as the sigmoid function): For millennia, a minority of prehistoric people could drink milk without having a stomach ache, flatulence, or diarrhea.

Only around 4,000-3,000 years ago, the curve exploded upwards and has remained so until today when a third of the world's population, the majority of European or Middle Eastern origin, can drink milk without problems.

“The consumption of milk is a necessary requirement, but the persistence of lactase requires other processes”

Eneko Iriarte, researcher at the Human Evolution Laboratory of the University of Burgos

That there were several millennia of difference between the significant consumption of dairy products and the generalization of the ability to digest lactose means, for the authors of this research, that the idea of ​​evolutionary convergence falls.

"The consumption of milk is a necessary requirement, but the persistence of lactase requires other processes," says Iriarte.

Which?

A few years ago the hypothesis of calcium assimilation dominated.

In its summarized version, having the enzyme also in adults would favor the supply of vitamin D and calcium (and its absorption) to those who did not have the most natural source of fixation: the action of solar radiation on the skin.

However, this could be valid for northern Europeans, but in the south there were no problems of hours of sunshine.

In Spain, for example,

The 2014 study with 18 individuals from El Portalón ends with a last sentence that could then seem like a risky hypothesis: “In famine conditions, the consequences of high consumption of foods with lactose in individuals without lactase persistence (particularly diarrhoea) would be more severe than in well-nourished non-lactase-persistent individuals, perhaps leading to high but occasional selection differences.”

In other words, it would not be so much that the genetic mutation offered an advantage in general to those who carried it, but rather that those who were lactose intolerant had less chance of getting ahead when they came badly.

The professor at the University of Burgos José Miguel Carretero was co-author of that 2014 study and also signs the current one in

.

“Then we saw that the Neolithic people of El Portalón were intolerant and that they were no longer so in the Bronze Age [between 4,000 and 3,000 years ago].

But we had little data.

It was a hypothesis, but now it seems that it was a global process”, says Carretero.

As they see it, instead of a positive synergy between the consumption of milk and the beneficial effects of consuming a liquid that is as rich as it is relatively free of pathogens, the relationship between this consumption and the persistence of lactase was of another type.

In a context prone to crises: first settlements turned into targets of attacks, coexistence with animals and their zoonoses, scarcity of resources..., health would be sporadically compromised and, in those moments, milk would be a resource vital for everyone, except for the intolerant.

“If you're healthy, you're lactose intolerant and you drink a lot of raw milk, you can get some cramps, maybe some diarrhea, and you'll have gas.

It won't be pretty, and it can be embarrassing, but you're not going to die from it.

However, if you are malnourished, and, therefore, weakened, and you also have diarrhea from drinking a lot of raw milk, then you have problems that endanger your life”, concludes Carretero.

To defend the role of hunger and disease, the authors of the study related their two maps, milk consumption and lactase persistence, with other events and phenomena such as climatic crises, known famines, collapses of the agrarian production... And they saw that there was a direct relationship between these moments of crisis and the increase in milk consumption.

In a collective note, the authors conclude: “Under these conditions, consuming milk would have resulted in increased mortality rates, with individuals lacking lactase persistence being especially vulnerable.

This situation would have been further exacerbated under famine conditions, when rates of disease and malnutrition increase.

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