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The origins of modern humans’ long-standing love affair with carbohydrates may date back to before we existed as a species, according to a new study.
There was once a widespread stereotype that ancient humans ate mammoth steaks and other chunks of meat, leading to the idea that the diet was high in protein, which is necessary for the development of large brains.
However, recent archaeological evidence has challenged this view, suggesting that humans developed a taste for carbohydrates long ago, roasting foods such as tubers and other starchy foods. Detected by analyzing bacteria It got stuck in my teeth.
New research published in journals science Thursday provides the first genetic evidence for an early carbohydrate-rich diet. Scientists have traced the evolution of genes that allow humans to more easily digest starch by breaking it down into simple sugars that can be used for energy. The study revealed that these genes were being duplicated long before the advent of agriculture.
This expansion may even date back hundreds of thousands of years, long before our species, Homo sapiens, or even Neanderthals, emerged as a separate human lineage.
Researchers based at the Jackson Laboratory in Farmington, Connecticut, and the University at Buffalo, New York, analyzed the genomes of 68 ancient humans. The research team focused on a gene called AMY1. This gene allows humans to use this gene to identify and begin to break down complex carbohydrate starches in the mouth by producing the enzyme amylase. Without amylase, humans cannot digest foods such as potatoes, pasta, rice, and bread.
Humans today have multiple copies of this gene, but the number varies from person to person. But it has been difficult for geneticists to figure out how and when the number of these genes increased. It is thought to reflect a time when eating starch became advantageous for human health.
“The main question we were trying to answer was when did this duplication occur? That’s why we started studying ancient genomes,” said the study’s first author, said Feyza Yilmaz, a computational scientist at the Jackson Laboratory.
“Previous studies have shown that there is a correlation between AMY1 copy number and the amount of amylase enzyme released in saliva. We believe that this is an event that corresponds to the emergence of agriculture. “I wanted to know if that’s the case. This is a hot question,” she said.
The researchers found that, dating back 45,000 years, hunter-gatherers (whose lifestyle predates agriculture) had an average of four to eight copies of AMY1. This suggests that Homo sapiens had a taste for starch long before the domestication of crops. human diet.
The study also revealed a duplication of the AMY1 gene in the Neanderthal and Denisovan genomes. extinct humans First discovered in 2010, little is known about the person. The presence of multiple copies of this gene in three human species suggests that it was a trait shared by a common ancestor before the different lineages split, according to the study.
This discovery means that ancient humans had multiple copies of AMY1 800,000 years ago.
It is not clear exactly when AMY1 first replicated, but it may have happened randomly. The presence of multiple copies created genetic opportunities that provided an advantage for humans to adapt to new diets, especially starch-rich diets, when they encountered different environments.
The analysis also showed that the number of AMY1 copies humans have has increased rapidly over the past 4,000 years. This is thought to be due to natural selection as humans adapted to a starch-rich diet as a result of the transition from a hunter-gatherer lifestyle to agriculture and grain cultivation. .
Taylor Hermes, assistant professor in the anthropology department at the University of Arkansas, said the study provides “compelling evidence” for how the molecular machinery that converts difficult-to-digest starches into readily available sugars evolved in humans. provided,” he said. I am involved in research.
Additionally, he noted that the new study supports a new theory that carbohydrates, not proteins, provided the energy increase needed to increase human brain size over time.
“The authors found that the copy number of the amylase gene increases, resulting in improved degradative capacity. Starch appeared hundreds of thousands of years ago, giving more credence to the idea that Neanderthals and Denisovans metabolized starch into simple sugars to facilitate the development of rapidly growing brains during human evolution. “It could have been,” Hermes said.
“While we think further testing using higher quality ancient human genomes is needed, we were surprised that the authors were able to detect multiple copies of the amylase gene in previously published Neanderthal and Denisovan genomes. ” added Hermès. “This demonstrates the value of continuing to mine the genomes of our human ancestors for important medical and physiological records.”
Understanding how individual genes change over time within a population is difficult, and the study is “very impressive,” said John L. Loeb, associate professor of social sciences and humanity at Harvard University. said Christina Werner, a professor of science.
“We know that changes in diet have played a central role in human evolution…but reconstructing these events as occurring thousands, hundreds of thousands, or even millions of years ago… It’s daunting,” said Wanner, who was not involved in the study. .
“The genomic investigation of this study ultimately helps to time stamp some of these major milestones and reveals intriguing clues about humanity’s long-standing relationship with starch.”
