Over the past 12,000 years, humans in Europe have evolved to better digest carbohydrates, increasing the number of genes responsible for breaking down starch from an average of eight to more than 11. This increase in gene copies coincides with the spread of agriculture in Europe, which introduced a diet rich in starchy foods such as wheat and grains. The enzyme amylase, which breaks down starch into sugar, is produced in saliva and the pancreas, and having more copies of the gene coding for this enzyme leads to higher levels of protein production.
The study, published in the journal Nature, highlights a new method for identifying the causes of diseases linked to genes with multiple copies in the human genome, such as the amylase genes. Led by researchers from the University of California, Berkeley and the University of Tennessee Health Science Center, the study found that Europeans today have an average of seven copies of the salivary amylase gene, compared to four copies 12,000 years ago. This increase in gene copies is thought to provide a survival advantage for ancestors with better abilities to digest starch.
The research also revealed that populations in other agricultural regions worldwide have shown similar increases in amylase gene copies, suggesting a shared evolutionary response to changing diets. The rate of evolution leading to changes in amylase gene copy numbers was found to be 10,000 times faster than that of single DNA base pair changes in the human genome. These findings shed light on the rapid genetic adaptations that have occurred over the past 12,000 years in response to increased carbohydrate consumption.
The study’s focus on amylase genes provides insights into other areas of the genome that have undergone rapid duplication in recent human history, including genes associated with the immune system, skin pigmentation, and mucus production. By utilizing long-read sequencing techniques, researchers were able to analyze the complex region of the human genome where amylase genes are located. This method allows for a more accurate assessment of genetic diversity and evolutionary history, enhancing our understanding of gene duplication events.
Analysis of contemporary human genomes revealed the presence of 28 different haplotype structures clustered into 11 groups with unique combinations of amylase gene copy numbers. The researchers identified an initial duplication event 280,000 years ago that added two copies of the AMY1 gene to the human genome. This early genetic change set the stage for later adaptations related to increased fitness in populations with more copies of amylase genes, particularly in the context of agriculture.
The study provides a foundation for further research into the genetic causes of diseases, such as tooth decay, associated with variations in amylase gene copies. By expanding our understanding of rapid evolution in response to dietary changes, this research opens up new possibilities for exploring the genetic underpinnings of complex traits and diseases in humans and other species. The innovative methods employed in this study offer a valuable tool for investigating genetic associations and evolutionary history in diverse populations.
