It turns out there’s a whole lot of wisdom hiding within gorilla poop. A new study has sifted through huge amounts of poop belonging to all kinds of great apes (that includes humans) and Old World monkeys to find out more about their gut flora, the universe of microorganisms that hang out in all of our digestive tracts.

Not only has this analysis helped to uncover how the human microbiome evolved, but it’s also showing us just how crappy the 21st-century diet really is. The study can be found in the open-access journal Nature Communications.

Despite these great apes being some of our closest living relatives, the researchers discovered that we have a less diverse microbiome than wild western lowland gorillas and chimpanzees living the Sangha region of the Republic of Congo. The microbes in the guts of gorillas and chimpanzees also tended to change in response to seasonal rainfall patterns, when their diets switch from fleshy fruits in the dry summer period to fiber-loaded leaves or bark the rest of the year.

Interestingly, a similar seasonal pattern can be seen within the Hadza people of Tanzania who live a hunter-gatherer lifestyle and rely on the seasonal availability of foods. However, you can't see this pattern with humans living in the US, who live in an industrialized culture that doesn’t rely on seasonally available foods.

"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," lead researcher Allison L Hicks of Columbia University said in a statement.

All of this is important because gut flora has a truly profound impact on your immune system, your metabolism, and wider health – it even influences your emotions. After all, a considerable proportion of our body's total cell count is not actually human cells, it is gut bacteria. While it’s hardly news to hear that guzzling soda and eating steaks every night is not good for your body, this research further highlights how our high-protein, low-fiber industrialized diets could be affecting our health and happiness.

"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," added Williams. "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.”