New research suggets that certain gut bateria passed down to us over million of years since before we were human
A huge collection of microbes live in and on human body and a new research suggests some of those microbes have been with us even before we evolved into human.
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Science says humans, gorillas and primates like chimpanzees and bonobos evolved from single common ancestor called African apes. Around 10 million years ago, the three diverged from their original source and with them some of our gut bacteria too.
A combined team of researchers from The University of Texas at Austin and University of California, Berkeley analyzed the gut microbes of humans and compared them with human close relatives chimps and bonobos as well as gorillas and found that some of the bacteria in our gut passed down to us since before we became human.
“We are showing that some human gut bacteria are the direct descendents of gut bacteria that lived within our common ancestors with apes,” said lead researcher Andrew Moeller from UC Berkeley’s Museum of Vertebrate Zoology. “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 findings reflect that bacteria in our guts are not just determined by our environment or external factors like food, geography and medicine but also by our origins. These microbes have been co-evolving inside humans for a long time and the relationship between us and bacteria in our intestine is much older than we thought – at least 15 million years old.
"We've known for a long time that humans and our closest relatives, the great apes, harbor these bacteria in our guts," said Moeller, "and the biggest question we wanted to answer is, where did these bacteria come from? Did we get them from our environment or from our evolutionary history? And how long have they persisted in host lineages?"
To find the answers, researchers collected the feces samples from 24 gorillas living in Cameroon, 47 chimps from Tanzania, 24 wild bonobos from Democratic Republic of Congo as well as 16 people from Connecticut.
By analyzing the DNA of the microbes thriving in these feces, researchers were able to reconstruct the evolutionary tree of the bacteria and found that two of the major groups of bacteria in gut named Bacteriodaceae and Bifidobacteriaceae exactly matched the evolution of their hosts. In short, just as we share common ancestors, our gut bacteria too share same ancestry with the microbes carried by their original source.
“Once we calibrated the molecular clock, we were able to date the split of human and chimp bacteria at around 5.3 million years ago and the human-gorilla gut bacteria split at around 15.6 million years ago, which are roughly in line with what we know from fossil and genomic data of the hosts,” said Moeller.
“What’s most exciting to me is the possibility that this codiversification between bacteria and hosts could extend much further back in time. Maybe we can trace our gut microbes back to our common ancestors with all mammals, all reptiles, all amphibians, maybe even all vertebrates. If that's true, it's amazing."