Every meal you eat is digested with the help of the bountiful bacteria thronging your intestines. When you're done digesting, those bacteria are also part of what's excreted. Now, 1000-year-old piles of dried-out poop are offering insights into how the billions-strong bacterial ecosystems in the human gut have been altered by sanitation, processed foods, and antibiotics.
An international team analyzed eight ancient coprolites preserved by dryness and stable temperatures in three rock shelters in Mexico and the southwestern United States. Researchers radiocarbon dated the samples, some of which were excavated almost 100 years ago and stored in a museum, to between 0 C.E. and 1000 C.E.
But the ancient microbiomes also stood apart from their modern counterparts, for example lacking markers for antibiotic resistance. And they were notably more diverse, including dozens of unknown species."In just these eight samples from a relatively confined geography and time period, we found 38% novel species," Kostic says.bacteria, for instance, are virtually unknown in the industrialized gut microbiome and appear only occasionally in people living nonindustrial lifestyles today.