Why do we favor carbohydrates? Geneticists suspect it may be linked to our shared ancestors with Denisovans and Neanderthals.

Digestion begins in the mouth. This process is aided by specific enzymes found in our saliva. One of these enzymes, amylase, helps break down starches that are abundant in grain products and certain root vegetables. The AMY1 gene is responsible for the production of amylase in saliva. In the DNA of modern humans, it is common to find three copies of this gene. According to American researchers, this genetic trait was acquired by our ancestors around 800,000 years ago, prior to their divergence from Denisovans and Neanderthals. During the Bronze Age, European farmers experienced a significant evolutionary boost in the amylase gene.

2024-10-18 07:30:13https://naked-science.ru/article/biology/pochemu-my-predpochitaem

Amylase breaks down starch molecules into simpler sugars. In hominids, this process begins in the mouth and continues in the pancreas. An unusually high number of copies of the AMY1 gene, responsible for the production of salivary amylase, is associated with adaptations to agriculture when starchy foods began to appear in the diet.

“The more amylase genes you have, the more of this enzyme is produced, and the more starch you can effectively digest,” explained Omer Gechtchumen, a biology professor at the State University of New York at Buffalo (USA) and co-author of a study published in Science.

Gechtchumen and colleagues from other research institutions in the USA utilized optical genome mapping and long-read sequencing. These groundbreaking methods allowed them to read a segment of DNA with great detail to distinguish between copies.

The researchers analyzed the genomes of 68 ancient humans. The oldest sample from Siberia, dated to 45,000 years ago, contained six copies of AMY1 per diploid cell, while the oldest genome from Romania, dated to 34,000 years ago, had eight copies. This indicates that in Eurasia, prior to the advent of agriculture, the diversity of AMY1 copy numbers was quite significant.

DNA segment copies arise from a chromosomal rearrangement known as duplication. Among the eight archaic genomes studied, several copies of AMY1 were found in both eastern and western Neanderthals and one Denisovan individual.

According to Kwon Do Kim from Jackson Laboratory, the first duplication of AMY1 occurred over 800,000 years ago, long before the divergence of the three subspecies of humans.

“Thanks to the duplication of the amylase gene, humans were able to adapt to changing diets, as starch consumption sharply increased with the invention of new technologies and changes in lifestyle. Individuals with a higher number of AMY1 copies likely digested starch more efficiently and produced more offspring. They gained an evolutionary advantage over relatives with fewer copies,” Gechtchumen clarified.

As a result of the initial duplication in the human genome, three copies of AMY1 became established. This chromosome segment lost stability and began to create new variations. From three copies, one can have nine or revert to a single copy in a haploid cell.

In the last 4,000 years, Europeans have experienced a spike in the average number of amylase gene copies. The authors linked this to the spread of agriculture and a shift to a starchy diet. Earlier, scientists showed that domesticated animals, such as dogs and pigs, also had a higher number of amylase gene copies compared to animals that do not rely on a starchy diet.