You are what you eat, or so the saying goes. But it seems that the bacteria in our gut have a much longer history than anyone could have imagined, as it has been revealed that they have been evolving in step with us since our last common ancestor with gorillas, some 10 million years ago.
To look into the differences of the gut bacteria between four ape species, the team acquired fecal samples from wild primates living across Africa: chimpanzees in Tanzania, bonobos in the Democratic Republic of Congo, gorillas from Cameroon, and humans in Connecticut. They then looked at three groups of bacteria and ran genetic tests on them, looking specifically at the gyrase B gene.
The researchers found, to their surprise, that the evolution of the two major families of bacteria found in the guts of all African apes, including in our own, perfectly matches the evolutionary history of their hosts. The gut bacteria of the ancestral African ape followed the sequence of evolution known to have occurred, where first the group that led to gorillas split from our last common ancestor, followed by the lineage that gave rise to us, leaving the chimpanzee and bonobo split until last.
This was not what they expected, and is not how the evolution of gut bacteria is generally assumed to have occurred. It is usually thought that the bacteria that live in us are more likely to be determined by external factors, such as the environment in which we live, our diet, and even the medicines we consume, but instead, it seems, they reflect our evolutionary past. The researchers were surprised to find that the gut microbes that can enter us from many separate sources had continued to evolve in step with us over millions of years, being passed down through hundreds, if not thousands of generations.
“We are showing that some human gut bacteria are the direct descendents of gut bacteria that lived within our common ancestors with apes,” says Andrew Moeller, lead researcher of the study published in Science, in a statement. “It shows there has been an unbroken line of inheritance or transfer from one generation to another for millions of years, since the dawn of African apes.”
The team now plan on extending their study further, looking not only at primates, but getting samples from all major groups of mammals. They hope to identify if – as now seems likely – all mammals have evolved their gut bacteria from a single common ancestor.