3.8-billion-year-old find in Canada offers more evidence that life was around very early after the Earth formed. These structures may not be the remains of ancient bacteria or archea. They may have formed via chemical garden process, the inorganic growth of tubular structures that had a semipermeable membrane at a redox boundary.
“Very similar structures were found before, in deep sea hydrothermal vents”, states Dr. Crispin Little in a paper he co-wrote in 2004. Mr. Little discovered tubular structures in a fault zone that he interpreted as generated by a chemical garden and the place where the oldest known fossils have been discovered.
Oldest known fossils: Fossilized bacteria?
Geologists suspect that the chemical garden phenomena may have played an important role in the emergence of life, that an inorganic semipermeable boundary preceded the organic cell wall, the lipid cell wall replaced the chemical garden. Though, that said, it’s interesting that they found isotopically light carbon, apatite and magnetite associated with the structures. This lends weight to the idea they are fossil bacteria.
A similar, older, study ran up against similar arguments regarding the debate around structural features suspected to be biogenic / abiogenic in origin. Evidence of isotopically light carbon provides strong evidence in support of such arguments, seeing as modern day analogs (micro tubular textures) are structurally identical (modern compared to billion year old fossils).
Could life have come shortly after Earth was formed?
It only takes one convincing example of a fossil from very ancient rocks to support the idea that life arose very quickly after the Earth’s formation. It does not matter if there’s just one example. Up to 15-20 years ago, many scientists thought life arose around 1 billion years after the formation of the Earth, as late as 3.5 billion years ago; that life emerged gradually via a stepwise increase in chemical complexity.
This now seems increasingly unlikely. It is indeed very interesting that life may have formed at little as 0.5 billion years after the formation of the Earth. Also, it’s important to remember that the first 200 million years of Earth’s history were too hot (4.55-4.35 Ga), so that leaves 4.3 billion – 4 billion years as the window of opportunity.
Life wiped out over and over again
But also, that time period around 4 billion years ago, was likely punctuated several great asteroid impacts that serialized the entire Earth, caused by the late heavy bombardment (LHB). Thus, life may have emerged several times, wiped out by giant asteroid impacts. It seems life only took 100 to 200 million years to emerge from non-life. This is a very brief period of time.
This is no doubt an amazing discovery, but dating back to that time period is extremely challenging. As such, I look forward to what rigorous peer reviews will bring us. The time scales are fascinating. It took less that half a billion years for a kind of proto-life to spring up, but then 2 billion more for eukaryotes, and another 1.5 billion for multi-celled life. Seems that life on Earth sprang up almost instantly but only became picturesque rather recently, geologically speaking.