2024-10-18 03:51:00
Some people think bread is the best thing about a ham sandwich. The crunch of the crust, the spongy crumb… Impossible to resist. And many are addicted to pasta in its many variations or drool at the idea of paella or risotto. All of these foods are starchy carbohydrates, and if you can’t reduce your intake, no matter what the scale suggests, you can always blame your genes.
A team of researchers has identified when the first duplication of the salivary amylase gene (AMY1) occurred, which helps break down starch in the mouth, which is the first step in metabolizing foods like bread and pasta. According to what they say this Thursday in the magazine ‘Science’, This change, which has influenced our diet to this day, occurred at least 800,000 years ago, long before the advent of agriculture.
Researchers have long known that humans carry multiple copies of AMY1. However, until now it has been extremely difficult to identify how and when the number of these genes expanded. The new study, led by the University at Buffalo (UB) and the Jackson Laboratory (JAX), shows how the first duplications of this gene laid the foundation for the wide genetic variation that still exists today, influencing how effectively Humans digest starchy foods.
“The idea is that the more amylase genes you have, the more amylase you can produce and the more starch you can digest efficiently,” explains Omer Gokcumen, a professor in the Department of Biological Sciences in the Faculty of Arts and Sciences at UB. Amylase, the researchers explain, is an enzyme that not only breaks down starch into glucose, but also gives bread its flavor.
By analyzing the genomes of 68 ancient humans, including a 45,000-year-old sample from Siberia, the research team found that pre-agricultural hunter-gatherers already had an average of four to eight copies of AMY1 per diploid cell, suggesting that Humans were already walking around Eurasia with a wide variety of high copy numbers of AMY1 long before they began domesticating plants and eating excessive amounts of starch.
Even in Neanderthals
The study also found that AMY1 gene duplications occurred in Neanderthals and Denisovans. “This suggests that the AMY1 gene may have first duplicated more than 800,000 years ago, long before humans split from Neanderthals and much earlier than previously thought,” said Kwondo Kim, one of the lead authors of this study from JAX’s Lee Laboratory.
“The initial duplications in our genomes laid the foundation for significant variation in the amylase region, allowing humans to adapt to dietary changes as starch consumption increased dramatically with the advent of new technologies and lifestyles .” explains Gokcumen.
According to the researchers, the initial duplication of AMY1 was like the first ripple in a pond, creating a genetic opportunity that later shaped our species. As humans expanded into different environments, flexibility in AMY1 copy number provided an advantage in adapting to new diets, particularly starchy ones.
“After the initial duplication, which gave rise to three copies of AMY1 in one cell, the amylase locus became unstable and began to generate new variations,” explains Charikleia Karageorgiou, one of the lead authors of the UB study. “From three copies of AMY1 you can get up to nine copies, or even go back to one copy per haploid cell.”
Even in pets
The research also highlights how agriculture has influenced variation in AMY1. While early hunter-gatherers had more gene copies, European farmers noticed an increase in the average copy number of AMY1 over the past 4,000 years, likely due to their starch-rich diet. Gokcumen’s previous research has shown that even domesticated animals that live alongside humans, such as dogs and pigs, have higher AMY1 copy numbers than animals that don’t rely on high-starch diets.
“It is likely that individuals with a higher copy number of AMY1 digested starch more efficiently and had more offspring,” suggests Gokcumen. “Ultimately, their lineages performed better over a long evolutionary period than those with lower copy numbers, which spread the copy number of AMY1.”
The findings are consistent with a study conducted by the University of California, Berkeley, published last month ‘Nature’, which found that humans in Europe have expanded the average copy number of AMY1 from four to seven over the past 12,000 years.
“Given the key role of AMY1 copy number variation in human evolution, this genetic variation represents an exciting opportunity to explore its impact on metabolic health and uncover the mechanisms involved in starch digestion and glucose metabolism.” says Feyza Yilmaz, associate computational scientist at JAX and lead author of the study. “Future research could reveal its precise effects and timing, providing critical information about genetics, nutrition and health.”
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