When did the duplication of a gene responsible for breaking down complex carbohydrate starch in the mouth occur?

It has long been known that humans carry multiple copies of a gene that allows us to begin breaking down complex carbohydrate starch in the mouth, providing the first step in metabolizing starchy foods like bread and pasta. However, it has been notoriously difficult for researchers to determine how and when the number of these genes expanded. A new study reveals how the duplication of this gene — known as the salivary amylase gene (AMY1) —may not only have helped shape human adaptation to starchy foods, but may have occurred as far back as more than 8,00,000 years ago, long before the advent of farming. The study ultimately showcases how early duplications of this gene set the stage for the wide genetic variation that still exists today, influencing how effectively humans digest starchy foods. Amylase is an enzyme that not only breaks down starch into glucose, but also gives bread its taste. Analysing 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 AMY1 copies per diploid cell, suggesting that humans were already walking around Eurasia with a wide variety of high AMY1 copy numbers well before they started domesticating plants and eating excess amounts of starch. The study also found that AMY1 gene duplications occurred in Neanderthals and Denisovans.