They’ve gone back ad forth with the Western Australian stromatolites (= life/not life) but recent evidence suggests life. Our physics color commentator Rob Sheldon, author of Genesis: The Long Ascent (Vols 1 & 2), offers some background:
Kranendonk has been doing stromatolite work since at least 2003, so he’s not a newcomer to the field. Generally speaking, everyone acknowledges that stromatolites are fossilized blue-green algae communities that have grown pillars over a couple of centuries. Shark Bay Australia is a famous site of stromatolites that are still growing.
Usually the debate circles around whether an old rock is an authentic stromatolite or not. Some less reputable astrobiologists have claimed that striated cherts from Australia were 3.85 billion year old stromatolites, but I don’t think that claim has held up.
Kranendonk is really happy to have isolated some organic compounds from a 3.5billion year stromatolite. His academic page at New South Wales university says that the paper is “in press”. I could not locate it from Google Scholar or arXiv.org. My best guess is that he has found something organically simple such as polycyclic aromatic hydrocarbons (PAH), if only because 3.5 billion years is a long time for organics to survive, and PAHs are the sort of keratonized (turned into keragen) that is stable. But then he says he found it under the electron microscope, which measures only atomic abundances. So I’m guessing these PAHs are found as a “carbon sheath” or layer surrounding fossilized blue-green algae, which just happens to be the same discovery as Richard Hoover on meteorites.
Well, keep digging!
See also: Stromatolites from 3.5 bya really ARE microbial life, say researchers.This doesn’t leave a lot of time for Darwinian evolution (natural selection acting on random mutation). Not nearly enough, in fact.
A bit of history (life to non-life, then back to life):
Researchers Suggest: Life Began On Land Not Sea. And Nearly 600 Mya Earlier Than Thought (2017)
World’s “Oldest Microfossils” Are Not Life Forms After All (2015)
Microbial Mats Show Fossil Structures From 3.5 Billion Years Ago (2014)
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