Our ancient DNA may have shaped our love for bread, pasta, rice, and other carbohydrates. It has long been known that our species has multiple copies of a gene that allows us to begin breaking down complex carbohydrates in our mouths. Although this first step in metabolizing starchy foods is well-documented, it has been difficult to pinpoint exactly how and when the number of carbohydrate-processing genes increased.
The new research Salivary amylase gene (AMY1) It may have begun more than 800,000 years ago, long before humans began farming. These duplications, which still exist today, opened the door to a wide range of genetic variations that aid in the digestion of starchy foods. For more information on the survey results, please visit The study was published Oct. 17 in the Advanced Online issue of the journal science.
It’s all in amylase
Amylase is digestive enzymes It breaks down starch into glucose, which the body can use as fuel. It is produced in the pancreas and salivary glands and also gives the flavor to bread.
“The idea is that the more amylase genes we have, the more amylase we can produce and the more starch we can digest effectively,” says study co-author Omar Gokmen, an evolutionary anthropologist at the University at Buffalo. stated in a statement.
[Related: How farming helped humans evolve to get more energy from carbs.]
in studyGokcumen uses optical genome mapping and long-read sequencing to AMY1 gene region. Typically, short-read sequencing methods have difficulty distinguishing between gene copies in this region precisely because the sequences are nearly identical. long read sequence This allowed the research team to look at the genes of modern humans and get a clearer picture of how AMY1 duplications evolved over time.
They analyzed the genomes of 68 ancient humans, including one 45,000-year-old sample taken from Siberia. They found that pre-agricultural hunter-gatherers already had an average of four to eight copies of AMY1 per diploid cell. This suggests that early humans in Eurasia were already A wide variety of AMY1 copies Long before they domesticated plants such as wheat and increased their starch intake.
The researchers also found that duplication of the AMY1 gene occurred in both Neanderthals and Denisovans.
“This suggests that the AMY1 gene may have first been replicated more than 800,000 years ago, long before humans separated from Neanderthals, further back than previously thought. study co-author Kwon-do Kim, a computational biologist at the Jackson Institute for Genomic Medicine. In the state of Connecticut, stated in a statement.
According to the teamthese initial duplications in our genome were the ones that laid the basis for major mutations in the amylase region. This has allowed our species to adapt to major dietary changes as starch consumption increases dramatically.
The beginning of genetic mutation
This first duplication of AMY1 was the first domino to fall in a sequence that created a huge genetic opportunity that would later form our species. As humans spread into warm and cool environments with a variety of food sources, the flexibility in the number of AMY1 copies allowed them to adapt to new diets, especially those rich in starch.
“After the initial duplication, resulting in three copies of AMY1 in the cell, the amylase locus became unstable and began to generate new mutations,” said study co-author Charikleia Karageorgiou, an evolutionary geneticist at the University at Buffalo. said. stated in a statement. “From three AMY1 copies, you can get up to nine copies or go back to one copy per haploid cell.”
The study also shows how agriculture itself influenced variation in AMY1. While early hunter-gatherers had multiple copies of the gene, the average number of AMY1 copies has skyrocketed over the past 4,000 years in early European farmers. This may be due to a diet high in starch. Previous studies have shown that livestock living in coexistence with humans also have higher AMY1 copy numbers compared to animals that rely less on starchy diets.
“Individuals with higher AMY1 copy numbers are likely to digest starch more efficiently and leave more offspring,” Gokmen said. “Their lineage ended up doing better over a longer evolutionary time frame than lower copy number lineages, increasing their AMY1 copy number.”
[Related: Scientists build intricate Neolithic family tree from 7,000-year-old DNA.]
These findings are also consistent with: Research published in September They found that European humans increased their average number of AMY1 copies from four to seven over the past 12,000 years.
“Given the important role of AMY1 copy number variation in human evolution, this genetic variation presents an exciting opportunity to investigate its effects on metabolic health and uncover mechanisms involved in starch digestion and glucose metabolism. ,” said study co-author Feiza, a computational scientist at the Jackson Laboratory. Yilmaz stated in a statement. “Future research will uncover its precise effects and timing choices, which may provide important insights into genetics, nutrition, and health.”
