Our old friend ethanol
How a person became an alcoholic
Our ancestors became addicted to alcohol as soon as they got down from the trees
Nadezhda Markina, "Newspaper.
Scientists have traced the history of a person's relationship with alcohol. It turned out that our distant ancestors learned to effectively split ethyl alcohol thanks to a mutation that arose 10 million years ago.
A person became addicted to alcohol long before he began to produce it, even long before he became a man. The ability to process alcohol has its roots in the very distant past: it originated in our ape-like ancestors as early as 10 million years ago, scientists write in an article in the journal PNAS (Carrigan et al., Hominids adapted to metabolize ethanol long before human-directed fermentation).
There is a tendency in medicine to explain the diseases of civilization by the fact that a person is not genetically adapted to a modern lifestyle. For example, a person simply did not have time to adjust his metabolism to the consumption of large amounts of sugar. As a result, he pays for a sweet life with obesity, hypertension and diabetes. It would seem that diseases caused by alcohol can occur for the same reason – because of the genetic maladjustment of the body.
According to historical beliefs, alcohol was not included in the "Paleolithic diet", nor was it in the diet of human ancestors. It appeared when a person mastered agriculture and faced the need to store food for the future. It is assumed that the technology of fermentation of food for its preservation appeared about 9 thousand years ago.
According to another hypothesis, primates could process alcohol as early as 80 million years ago. They feed on fruits, and in overripe fruits yeast is produced, which, as well as in the manufacture of wine, ferment sugar into alcohol. Eating overripe fruits, primates consume alcohol.
The team led by Professor Stephen Benner, a synthetic life specialist who created the Applied Molecular Evolution Foundation (FRAME), tried to figure this out and understand how much time a person had for his metabolism to adapt to alcohol consumption.
Ethyl alcohol – ethanol – is broken down in the liver. The main enzymes of its metabolism are alcohol dehydrogenase, which converts an ethanol molecule into acetaldehyde molecules, and aldehyde dehydrogenase, which cleaves acetaldehyde to vinegar and water.
To find the answer to the question, scientists traced the fate of the enzyme alcohol dehydrogenase class IV (ADH4) in the evolution of primates for 70 million years.
They did not just study how the enzyme changed, they tested it in modern primates for its effectiveness against ethanol and calculated its activity in ancient extinct species. It turned out that almost all enzymes in primates could not break down ethanol until some point in their evolution, although they could break down some other alcohols.
The last common ancestor of humans and orangutans was unable to process ethanol from food. The situation radically changes at the moment of separation of the branch of orangutans from the branch of chimpanzees, gorillas and humans. In the common ancestor of chimpanzees, gorillas and humans, the enzyme ADH4, as scientists have shown, broke down ethanol 40 times more efficiently than in earlier primates.
This radical increase in the catalytic activity of the enzyme occurred due to a single amino acid substitution in the protein molecule. In the experiment, the scientists checked — it is the replacement of the amino acid at position 294 that leads to the fact that ADH4 begins to break down ethanol.
So one mutation led to the fact that primates began to process ethanol contained in overripe fruits. Using paleoanthropological data, scientists claim that this happened in time during the period of changed environmental conditions in the early Miocene and Oligocene. It was then that the ancestors of man began to climb down from the trees and gradually adapted to the terrestrial lifestyle.
Paleoanthropologists find such adaptations in early hominids such as orrorin (6 million years ago) and sahelanthropus (7 million years ago). Having descended to earth, human ancestors began to collect more often overripe falling fruits, which contain much more ethanol than fruits plucked from branches. The ability to incorporate ethanol into the metabolism and get energy from it contributed to survival.
Advertisement of the liqueur "Anise of the monkey" (Barcelona, photo Marina D'ecclesiis)
Interestingly, modern great apes differ in their eating habits depending on whether they can break down ethanol. Orangutans and gibbons, which cannot break down ethanol, eat both ripe and unripe fruits, while chimpanzees and gorillas, who can do this, prefer ripe ones.
As for the person, he eventually successfully mastered the production of alcohol. And the ability useful for survival turned into a considerable problem for him, which is called alcohol addiction. And here many other genes have already been involved, which scientists are trying to figure out in order to fight this addiction.
So, experts from the University of Texas in the journal Molecular Psychiatry described a whole network of genes involved in alcoholism. They compared the work of genes in brain tissue taken posthumously from alcoholics and alcohol-independent people. They were able to identify a pool of genes that, working together, distinguish the brain of alcoholics. This made it possible to directly link some features of alcohol dependence with the work of certain genes. Scientists were able to build a genetic model of alcoholism. They hope that this model will allow them to find new ways to treat it.
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02.12.2014