Many people refuse drink milk claiming that humans are the only animal that continues to take it after weaning. So it’s supposedly not natural. But aside from what’s natural isn’t always the best, it’s also true that humans, at least a good portion of us, have a protein that helps us digest lactose. What other animals lose when they become adults. Always thought that what made us evolutionarily resistant to lactose it was our stubbornness. Since we didn’t stop drinking milk, we ended up being able to do it without any problems. However, a new study points to something else.
In this work, published in Nature, shows that our ancestors already drank milk 9,000 years ago. However, the gene that allows us to digest lactose without problems was first discovered in individuals 5000 years old and did not become widespread in Europe until about 3000 years ago. Come on, our ancestors drank milk for 6000 years, not tolerating it well. Some are bold, no doubt.
Although in fact this study shows that it did not take much courage to do so, mainly because they didn’t feel bad. If this were the case, then this genetic trait would have been selected much earlier. A key factor behind the before and after digestion of lactose was the appearance of the first human settlements. But what does this have to do with anything?
Before we begin: what is lactose intolerance?
Lactose is the most abundant sugar in milk. Formed by union one molecule of glucose and one molecule of galactoseboth are well tolerated by our digestive system. However, all lactose is difficult to process, so it can give us intestinal discomfort.
This would be a problem for baby mammals (including human babies) so they have a protein called lactasewhich helps break these bonds and break down lactose into glucose and galactose.
The point is that as mammals get older and outgrow weaning, they begin to lose their lactase support. It only stays in those who have a genetic trait known as lactase resistance. If they don’t have it, they will have what we know as lactose intolerance.
In the case of humans, this constancy is distributed very unevenly. For example, in Africa there are places where 80% to 90% of the population have lactose intolerance. In contrast, in Northern Europe the percentage is negligible.
In any case, it can be said that a significant part of people today can lactose intolerant. But in the past the situation was quite different. Genetic analysis done on prehistoric individuals shows that very few of them had lactase resistance. Therefore, it would be logical to think that they would not drink much milk.
Looking for milk pots
This study was carried out by an international team of scientists who carried out two very specific actions. On the one hand, they developed a series of computational models based on current UK Biobank data and ancient DNA, about 1700 prehistoric individuals. In this way they were able display and timeline for lactase persistence.
On the other hand, they analyzed animal fat present in ceramic remains from different eras. In this way, they were able to check which of these remains belonged to milk, and along with this, make another model, which they compared with the previous one.
Initially, it was expected that in places where they drink more milk, the persistence of lactase will appear earlier. But it wasn’t. In fact, nothing is further from reality. Did this mean that people drank milk, despite the fact that lactose intolerance? Do they mind getting sick?
The answer to this question was found in current data, in particular, in the British Biobank. It contains both genetic and habit information. 300,000 people. So it helped them see that there is little to no difference between those who are genetically lactose intolerant and those who are lactose intolerant. Most do not know this, so they continue to drink milk normally. It may cause them some minor digestive discomfortbut it’s almost imperceptible.
However, the situation is changing in places with poorer sanitation, where diarrheal diseases are more common. If this is combined with lactose intolerance, the result can even be fatal.
The key is in the settlements
Once in this data, the authors of the study again began to analyze the models they created. What if it wasn’t about drinking milk, it was about having diarrheal diseases what motivated us to tolerate lactose? And indeed, it was.
They saw it when they were growing up settlementswhere water sanitation was very poor, lactase tolerance was genetically selected. This is so because people would continue to drink milk whether they were lactose tolerant or not. The intolerant will die, and little by little genetic selection will take place. lactose tolerance. In addition, the effect was more dramatic, coinciding with the Holodomor.
So we actually became lactose tolerant not because we were stubborn, but because we were social. Well, for that and for having no idea how disinfect water. Today we already know how to do it well, but many of us have retained lactose tolerance. Those gases that we save are not bad.
Source: Hiper Textual
