Scientists have discovered 1.8 billion-year-old fossil microorganisms in fossilized deep-sea mud from Western Australia. It appears that the sulfur-cycling microbial community is almost identical to microbial fossils from 2.3 billion-years-ago, and to modern communities found off the coast of South America.

The stability of these communities could be evidence of a long-term lack of evolution, which reflects the lack of change in their environment. This would be an example of a theory known as evolution’s “null hypothesis.” When an environment is stable, and there are no pressures to cause natural selection, the population of microbes that live in the environment should be stable as well. Further study could help confirm if these mud-inhabiting organisms are an example of this important aspect of evolutionary theory.

The study was supported by the Astrobiology Program and the NASA Astrobiology Institute and published in the Proceedings of the National Academy of Sciences.

For more information, check out this press release from the University of California, Los Angeles