This article has been reviewed according to Science X's editorial process and policies. Editors have highlighted the following attributes while ensuring the content's credibility: We often think of microbes as organisms that live around us, like the Salmonella bacteria and flu viruses that cause illness. But some of our most intimate relationships are with the microbes living inside us.
Incredibly, about half of the cells in the human body are microbial inhabitants. Scientific attention to the microbiome has helped us understand how many of them support our health, for example, by helping us digest food or supporting our immune system. Elsewhere in the animal kingdom, microbes forge even more remarkable partnerships with their hosts.
They help generate energy for coral and deep-sea tube worms and break down stubborn molecules like cellulose and lignin within animals as varied as cows and termites. They even help squid camouflage themselves. But how long have such partnerships existed?
New research led by Zhenfei Wang and Yongbo Peng from Nanjing University, on which I was a co-author, has found evidence of these close relationships between animals and microbes in a 550 million-year-old fossil from southern China. The research is published in the Proceedings of the National Academy of Sciences. Previously, the earliest evidence of symbiosis was documented in fossils 100 million years younger.
Tracing animal-microbe symbiotic relationships back hundreds of millions of years is extremely challenging. The fossil record has been altered, is incomplete and is biased toward organisms and environments that preserve well. Even exceptionally preserved fossils rarely retain evidence of the microbes that once lived within an animal.
This makes ancient symbiotic relationships very difficult to identify. Given these challenges, our international research team sought to explore geochemical fingerprints of past microbe-animal interactions. We specifically focused on the tubular fossil Conotubus that lived during the Ediacaran period, which extends from approximately 635 million to 541 million years ago.
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