Trillions of symbiotic microbial cells are harbored within human beings, a collection that’s known as the microbiota. The set of genes within these cells is referred to as the microbiome, and there’s an increasing understanding that gastrointestinal microbiome has a crucial impact on metabolism, immunity, and overall health. However, exactly how the microbes living in our guts and mouths affect us is still a topic of pursuit, and in a recent effort to learn more about human health, scientists turned to some of our closest relatives for help: gorillas and chimpanzees.

More specifically, they turned to their poop. In a study published Thursday in Nature Communications, scientists from the Wildlife Conservation Society and Columbia University’s Center for Infection and Immunity explain that they studied fecal samples belonging to wild chimps and gorillas in an effort to learn more about the evolution of the human microbiome. Over the course of three years, they applied genetic sequencing technology to the ape dumps, a process that revealed the microbiomes of these animals fluctuated with seasonal rainfall patterns and diet. Their gut microbes were different when they ate mostly succulent fruits during dry summers compared to the rest of the time when they predominantly ate a fiber-rich diet of leaves and bark.

That change in microbiome, the scientists note, is a lot like the switch witnessed in the gut flora of the human Hadza hunter-gatherers who live in Tanzania. They too eat what’s available because of the changing seasons. People who live in industrialized communities, however, are different. Just because it’s not strawberry season doesn’t mean that grocery stores aren’t carrying the goods. In turn, that means that the microbiome of humans living in cities and suburbs — places where food isn’t dictated by seasons — have microbiota that are quite different than those of apes.

What gorillas eat is based on seasonal availability. Max Pixel

“The fact that our microbiomes are so different from our nearest living evolutionary relatives says something about how much we’ve changed our diets, consuming more protein and animal fat at the expense of fiber,” senior author Brent Williams, Ph.D., explained in a statement released Thursday. “Many humans may be living in a constant state of fiber deficiency. Such a state may be promoting the growth of bacteria that degrade our protective mucous layer, which may have implications for intestinal inflammation, even colon cancer.”

Those chimps and gorillas are consuming a bunch of fiber, and the scientists note it’s bacteria that helps the apes break down the fibrous plants, and one year later another group of bacteria sweeps in to eat up the mucous layer that was sitting in the ape’s guts because of the months they spent gobbling up fruit.

“While our human genomes share a great deal of similarity with those of our closest living relatives, our second genome (the microbiome) has some important distinctions, including reduced diversity and the absence of bacteria and archaea that appear to be important for fiber fermentation,” the study’s first author, Allison Hicks, Ph.D., revealed in a statement. “Understanding how these lost microbes influence health and disease will be an important area for future studies.”

To the question of fiber: Yes, you should be consuming a lot more. Dietary fiber helps prevent or relieve constipation, lowers the risk of diabetes and heart disease, and helps people stay at a healthy weight. Unlike carbs and proteins, the body doesn’t digest fiber — instead, it takes a slip through the stomach, small intestine, and colon before a quick Irish goodbye via your butt. Most plant-based foods contain the two types of fibers you’re looking for, so the next time you’re cruising through Trader Joe’s, try to eat more like a gorilla.