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The ancient DNA of our ancestors may have significantly influenced our affinity for carbohydrates such as bread, pasta, and rice. It has been established that humans possess multiple copies of genes responsible for initiating the breakdown of complex carbohydrates in the oral cavity. While this initial phase of starch digestion is well understood, determining when and how these carbohydrate-processing genes proliferated has proven more challenging.
Recent studies suggest that early duplications of the salivary amylase gene (AMY1) may date back over 800,000 years—long before the advent of agriculture. These duplications paved the way for a diverse range of genetic variations that continue to aid in starch digestion today. The research findings were published on October 17 in an advanced online issue of the journal Science.
The Role of Amylase
Amylase is a crucial digestive enzyme responsible for converting starch into glucose, which serves as an energy source for our bodies. This enzyme is produced by both salivary glands and the pancreas and contributes to the flavor profile of bread.
According to Omer Gokcumen, co-author and evolutionary anthropologist at the University at Buffalo, “The premise is straightforward: having more amylase genes enables greater production of amylase itself, thereby enhancing one’s ability to digest starch effectively.”
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In their research, Gokcumen’s team employed optical genome mapping alongside long-read sequencing techniques to analyze the AMY1 gene region. Traditional short-read sequencing often struggles with accurately distinguishing between closely related gene copies due to their similar sequences; however, long-read sequencing provided clearer insights into how AMY1 duplications have evolved throughout history.
The researchers examined genomes from 68 ancient humans—including a specimen from Siberia dating back 45,000 years—and discovered that pre-agricultural hunter-gatherers possessed an average range between four to eight AMY1 copies per diploid cell. This indicates that early Eurasian humans had already developed significant genetic diversity concerning AMY1 long before they began cultivating starchy crops like wheat.
Additionally, it was found that both Neanderthals and Denisovans exhibited AMY1 gene duplications.
Kwondo Kim—a computational biologist at The Jackson Laboratory for Genomic Medicine—stated: “This implies that AMY1 likely underwent its first duplication over 800 millennia ago; this predates humanity’s divergence from Neanderthals by a considerable margin.”
The research team posits that these early genomic duplications laid down a foundation for significant variations within the amylase region. This adaptation enabled our species to respond effectively to substantial dietary shifts as starchy food consumption increased dramatically over time.
Catalyzing Genetic Diversity
The initial duplication event involving AMY1 can be likened to knocking over a domino—the first action triggering subsequent changes leading toward vast genetic opportunities shaping human evolution. As populations migrated across various climates with distinct food sources,
the variability in AMY1 copy numbers facilitated adaptations toward new diets rich in starches.
‘Following this primary duplication event resulting in three copies per cell,’ explained Charikleia Karageorgiou—a co-author and evolutionary geneticist at Buffalo University—’the locus associated with amylase became unstable and began generating new variants.’ She added: ‘From three copies you could see numbers rise up to nine or revert back down.’
A visual representation illustrating how variations within amylase genes evolved influencing human capacity for digesting complex carbohydrates like pasta or bread.CREDIT:The Jackson Laboratory.
THE STUDIES ALSO REVEAL HOW AGRICULTURE INFLUENCED VARIATIONS IN THE AMYLASE GENES.EARLY HUNTER-GATHERERS HAD MULTIPLE COPIES OF THIS GENE,BUT OVER THE LAST FOUR THOUSAND YEARS,A SURGE IN AVERAGE COPY NUMBERS WAS OBSERVED WITHIN EARLY EUROPEAN FARMERS.THIS IS LIKELY ATTRIBUTABLE TO THEIR STARCH-RICH DIETS.PREVIOUS RESEARCH HAS SHOWN THAT DOMESTICATED ANIMALS LIVING ALONGSIDE HUMANS TEND TO HAVE HIGHER NUMBERS OF THE AMYLASE COPY COMPARED TO THOSE NOT RELIANT ON STARCH-DENSE DIETS.
“Individuals possessing higher counts regarding their number Of Copies Were Likely More Efficient At Digesting Starch And Consequently Had Greater Reproductive Success,” stated Gokcumen.“Over Extended Evolutionary Timescales Their Lineages Ultimately Outperformed Those With Fewer Copies Propagating Higher Numbers Of The Am Y One Gene.”
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THESE FINDINGS ALIGN WITH A STUDY PUBLISHED LAST MONTH WHICH INDICATED THAT EUROPEAN HUMANS HAVE EXPANDED THEIR AVERAGE NUMBER OF COPIES FROM FOUR TO SEVEN OVER TWELVE THOUSAND YEARS.
“CONSIDERING THE SIGNIFICANT ROLE PLAYED BY VARIATION IN THE NUMBER OF COPIES FOR HUMAN EVOLUTION THIS GENETIC DIVERSITY OFFERS AN EXCITING AVENUE FOR INVESTIGATION INTO ITS IMPACT ON METABOLIC HEALTH AND UNDERSTANDING MECHANISMS INVOLVED WITH STARCH DIGESTION AND GLUCOSE METABOLISM,” SAID FEYZAYILMAZ,A COMPUTATIONAL SCIENTIST AT JACKSON LABORATORY.AND SHE ADDED,“FUTURE INVESTIGATIONS COULD UNCOVER PRECISE EFFECTS AS WELL AS TIMING SELECTION PROVIDING VALUABLE INSIGHTS INTO GENETICS,NUTRITION AND HEALTH.”
THE POSTOUR APPRECIATION FOR TASTEFUL CARBOHYDRATES MAY DATE BACK EIGHT HUNDRED THOUSAND YEARS APPEARED FIRST ONPOPULAR SCIENCE
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