Study finds most primates, including humans, can digest insects
According to a Rutgers study, insects—the food choice for our early primate ancestors—could still be eaten and digested by almost all primates today, including humans.
The thought of eating an insect makes most people cringe—at least those who live in the United States, Canada, and Europe, a minority of the world’s population who would not let a cricket, grasshopper, or beetle near their dinner table. The “yuck” factor, however, does not have anything to do with nutrition, digestion, or evolution. In fact, according to a Rutgers study, insects—the food choice for our early primate ancestors—could still be eaten and digested by almost all primates today, including humans.
“For a long time, the prevailing wisdom was that mammals didn’t produce an enzyme that could break down the exoskeletons of insects, so they were considered to be very difficult to digest,” said Mareike Janiak, a doctoral candidate in Rutgers’ Dept. of Anthropology and lead author of the study published recently in Molecular Biology and Evolution. “We now know from research on bats and mice, and now my research on primates, that this isn’t true.”
Janiak and collaborators from Kent State University discovered that almost all living primates still have working versions of the gene needed to produce a stomach enzyme that breaks down exoskeletons. The scientists looked at the genomes of 34 primates, searching for copies of a gene called CHIA, the stomach enzyme that breaks down chitin, which is part of the outer covering of an insect.
What they discovered is that while most living primates have only one copy of the CHIA gene, early primates, which tended to be very small, had at least three working copies. This shows that insects were an extremely important food source for our early ancestors. Some living primates, like the tarsier, which eats more insects than any other primates, and today exists only on islands in Southeast Asia, have five copies of the gene, because it was duplicated specifically in this lineage.
“As some primates evolved to be larger and more active during the day than at night, their diets shifted a bit to other foods like fruits and leaves,” Janiak said. “Insects became less important and their digestive enzymes changed, but most living primates still have at least one working CHIA gene.”