Evidence for Early Origin of Life on Earth

[BillTre]

Science news reports:
(original report abstract here)
Eleven micro-fossils though to be the remains of bacteria (some dispute this) from Australia dated to 3.5 billion years ago have been analyzed with secondary ion mass spectrometry (SIMS).
This has revealed different ratios of different weight carbon atoms suggesting they represent 5 different kinds of organisms.
"Two types of microfossils had the same carbon ratio as modern bacteria that use light to make carbon compounds that fuel their activities—a primitive photosynthesis that did not involve oxygen. Two other types of microfossils had the same carbon ratios as microbes known as archaea that depend on methane as their energy source—and that played a pivotal role in the development of multicellular life. The ratio of a final type of microfossil indicated that this organism produced methane as part of its metabolism."

The authors argue that this:
1) supports the claims that the fossils are biological in origin,
2) that bacteria and archaea have both evolved (diverged) prior to the formation of the fossils, and
3) supports claims or an earlier origin of life (perhaps 4 billion years ago).

#3 would support claims that life is not so difficult to get started (at least on earth).

 

[jim mcnamara]

If you accept that those are bacterial fossils, it does provide a strong assertion that abiogenesis is a frequent occurrence through out the universe. Our big problem right now is no first hand evidence for another non-Earth place where life evolved. Unless an alien intelligence makes itself known to us or we find early life some place like Enceladus, then we are stuck without any substantive proof of a second instance of life.

 

[Greg Bernhardt]

Our big problem right now is no first hand evidence for another non-Earth place where life evolved.

Just out of curiosity, is evolution to more complex forms guaranteed or could it be that abiogenesis although common throughout the universe, the conditions for supporting complexity are more rare and most life doesn't progress past bacterial size forms.

 

[BillTre]

Seems common enough on earth.
I am sure there people who would argue it should be.
Don't really know elsewhere though.

Arguments might use ideas like complexity will build on complexity (predators on non-predators, predators on those, etc.) or chnages in an environment will provide new niches for new forms.

 

[jim mcnamara]

I think the implication of the paper we're looking at is that very simple life forms may be found in many places. More advanced forms, no comment really. Advanced cell respiration would probably modify the original atmosphere, example: the Great Oxygenation Event on Earth. The advancements in terms of cell efficiency are due to organisms developing aerobic respiration which was only possible when free oxygen became available. This is one of the reasons why everyone is intensely interested in exoplanet atmospheres. Methanogenesis is another reason.