Our relationship with food is part of being human. Meals are time for ritual and a chance to strengthen social bonds over the work of cooking and eating. But what and how we eat also helped make us human, to begin with: Changes in our eating habits also shaped our genes.
Long ago, our ancestors lost the massive jaws and strong chewing muscles as invented tools to strip meat from bones and gained the ability to cook. But the alterations continued with the genes the govern our sense of taste. Many wild vegetables are bitter, a taste shunned by chimpanzees and our other living ape cousins. But something in ancient humans changed that allowed them to munch happily on roots and leafy greens that older lineages might have shunned. That something included the loss of two bitter taste genes, researchers have discovered.
The research group compared genes from modern humans, chimpanzees, a Neandertal and another ancient human called a Denisovan. They found that all three human groups lacked the genes called TAS2R62 and TAS2R64 while the chimpanzees hung on to them, reports Ann Gibbons for Science. The losses—along with that of a third gene called MYH16, which builds up muscles in a chimpanzee’s strong jaws—happened around the time hominin and chimpanzee lineages were splitting apart, the researchers write in the Journal of Human Evolution.
A fourth gene alteration crops up about 200,000 years ago, when our human ancestors diverged from the Neandertals and Denisovans. Gibbons explains:
Our lineage, for example, carries an average of six copies, and as many as 20 copies, of the salivary amylase gene, AMY1. The gene produces the enzyme amylase in our saliva, which has been thought to help digest sugars in starchy foods, although its role in human digestion is still unproven. By contrast, chimps, Neandertals, and Denisovans carry only one to two copies of the salivary amylase gene, which suggests they got fewer calories from starchy veggies than modern humans.
Together, the findings indicate that ancient humans would have noshed the wild equivalents of squash, gourds and yams even though they were bitter. Eventually they would have cooked the veggies and eventually bred the sweeter, less starchy versions we enjoy today. The genetic and culinary advances together meant that ancient humans had more calories available for less work. The extra energy went toward developing our brains.
After these changes, modern humans still exhibit diversity in the genes that code for taste. Such differences can be fodder for the forces of evolution in the future, but for now they explain why some people prefer bland foods or why others have a sweet tooth.