About 50,000 years ago, a bunch of Neanderthals made a house – and a bathroom–from what is now a rocky slope south of Valencia, Spain. In recent years, some of those paleo brushings, the oldest of which are known to come from a human species, have been unearthed and analyzed. Now, researchers have glimpsed the ecosystems that existed in the guts of those early hominins, from a fecal deposit in the remains of a site fire pit.
More than 200 bacterial microorganisms were extracted from the old poop by an interdisciplinary team of archaeologists, microbiologists and anthropologists. The researchers found a striking consistency between the microbial inhabitants of the Neanderthal gut and the type of microbes that inhabit the intestines of modern humans. That consistency shows that many of the minuscule inhabitants of our innards are actually long-standing inhabitants, living in us for hundreds of thousands of years, and have evolved along with the hominins that inhabit them. The investigation was published in the Nature journal Communications Biology.
According to Marco Candela, a microbiologist at the University of Bologna and co-author of the paper, the team wanted to “see which microbiomes co-evolve with the Gay lineage in evolutionary time. To do this, they looked for microbes that modern humans could share with Neanderthals.
Having an early reconstruction of a human gut is useful for contextualizing what our microbiomes look like today; researchers want to know which bacteria have remained with us and which have completely disappeared from our internal ecosystems. Microorganisms with considerable endurance in the guts of mammals have been called “old friends.” in the mid-2000s, and their co-evolution with us has been linked to the way humans have lived for hundreds of thousands of years.
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The oldest gut microbiome data for humans is about 8,000 years old – they don’t even predate the last Ice Age, which ended about 11,000 years ago. That has failed researchers when it comes to understanding the insides of our early ancestors. Neanderthal poo pushes the chronology back some 40,000 years – shortly before Neanderthals as we know them disappear from the evolutionary record.
“The thing is, we’ve identified some microorganisms shared by modern humans and Neanderthals,” Candela said. This means that these microorganisms populate the intestines of the human lineage before Neanderthal segregation and sapiens genders. “
A major find in Neanderthal poop was the uptake of short-chain fatty acid-producing bacteria, many of which enable people to get extra energy from dietary fiber, and one of these, according to the researchers, may have provided health benefits for old mothers and their children. But just as good microbes hitchhiked through time in our guts, so did the hell-raisers – the researchers also found bacterial pathogens in the feces present today that cause oral and dental disease in modern humans.
According to Candela, the microbiomes of populations that live in traditional rural ways, such as the Hazda, a group of hunter-gatherers in northern Tanzania, have more guts. On the other hand are people who live in urban settings, who isolate our guts and make our bacterial residents less alike from person to person. The paper describes a great loss of bacterial diversity in the modern human gut and a situation where each of our guts don’t talk to each other as they did in our evolutionary past. “Each of us is like an island,” Candela said.
Often times, the human evolution path has been heroically framed – of many early humans, ours was the one that succeeded. But as the Neanderthal microbiome shows, we weren’t alone on that journey. Many microorganisms followed the same path.
“Based on these results, we can expect that the symbiotic time depth between humans and some microbes living together will be at least a million years,” wrote study co-author Stephanie Schnorr in a Nature blog on the research. “This implies a solid physiological relationship linked to normal development and longevity health in both humans and Neanderthals as an ancient legacy.”
Hopefully more feces will be studied in the future so we can further unpack the guts that made us who we are. For now, we can be grateful that the findings are not worthless.