People who advocate adding insects to the human diet may be channeling their distant ancestors.

Based on an analysis of the genomes of 107 different species of mammals, University of California, Berkeley, scientists conclude that our distant ancestors—the small, furry creatures that scurried around the feet of the dinosaurs 66 million years ago—were mostly insect eaters.

The scientists inferred this because the genes for the enzymes that allowed these early ancestors of all mammals to digest insects are still hanging around in nearly all mammal genomes today. Even animals like tigers and seals that would never touch an insect have nonfunctional pieces of these genes sitting in their chromosomes, betraying their ancient ancestors’ diet.

“One of the coolest things is, if you look at humans, at Fido your dog, Whiskers your cat, your horse, your cow; pick any animal, generally speaking, they have remnants in their genomes of a time when mammals were small, probably insectivorous and running around when dinosaurs were still roaming Earth,” said postdoctoral fellow Christopher Emerling. “It is a signature in your genome that says, once upon a time you were not the dominant group of organisms on Earth. By looking at our genomes, we are looking at this ancestral past and a lifestyle that we don’t even live with anymore.”

The genetic evidence independently corroborates the conclusions paleontologists reached years ago based on the shapes of fossils and teeth from early mammals.

“In essence, we are looking at genomes and they are telling the same story as the fossils: that we think these animals were insectivorous and then dinosaurs went extinct. After the demise of these large carnivorous and herbivorous reptiles, mammals started changing their diets,” he said.

The finding could shed light on other roles played by these enzymes, called chitinases, which are found not only in the gut but the salivary glands, the pancreas, and the lungs, where they may be involved in asthma.

Emerling and colleagues Michael Nachman, a professor of integrative biology and director of the UC Berkeley Museum of Vertebrate Zoology, and Frédéric Delsuc of the French National Center for Scientific Research (CNRS) and Université de Montpellier in France, reported their findings May 16 online in the journal Science Advances. Emerling currently is a PRESTIGE & Marie Curie postdoctoral fellow in Montpellier working on the ConvergeAnt project.