A study published in the journal Proceedings of the National Academy of Sciences, describes the analyses showing that two of the 5 species studied appear to have carried out a primitive form of photosynthesis, another appears to have been able to produce methane gas, and two others appear to have consumed and used methane as a feedstock to build their cell walls.
In other words, almost 3.5 billion years ago we already had a complex living system. In addition to this, previous work by the same group of researchers responsible for this new study also showed that sulfur-consuming beings existed 3.4 billion years ago.
According to the researchers, this evidence that such a diverse group of organisms had already evolved so early in Earth’s history (our planet is about 4.6 billion years old), along with scientists’ knowledge of the vastness of galaxies and stars in the Universe, and that so many of these stars have multiple planets orbiting them, greatly strengthen the case that life exists in several other places in the Universe. since it would be extremely unlikely that life would have formed and evolved so fast on Earth and not have arisen anywhere else in the cosmos.
The results also suggest that life must have begun much earlier, perhaps more than 4 billion years ago, and show that it was not difficult for primitive life to form and evolve into more complex living organisms. This also supports another recent and controversial paper detailing fossils that may be around 4.28 billion years old.
The new study is the most detailed ever conducted on microorganisms preserved from such ancient fossils, which were first described in the journal Science in 1993 and explored biologically in a 2002 Nature publication. And now we have an in-depth breakdown of the type of organisms, what their metabolism was based on, and how biologically advanced or primitive they were.
The new research work analyzed the fossilized microorganisms with modern technologies called ‘secondary mass spectrometry’ (SIMS), which reveals the ratio of carbon-12 to carbon-13 (isotopes of the element carbon), information that scientists can use to determine how these beings lived, especially in metabolic terms (photosynthetic bacteria, for example, have different carbon signatures in relation to methane producers and consumers).
The fossils analyzed were formed at a time when there was very little oxygen in the atmosphere and it is likely that complex photosynthesis had not yet evolved. Gaseous oxygen actually emerged in the Earth’s atmosphere about half a billion years later, with its atmospheric concentration rising rapidly about 2 billion years ago. From there, molecular oxygen would have poisoned these microorganisms and killed them.
Organisms with primitive photosynthesis today are relatively rare because of two conditions necessary for their survival: minimal lighting and lack of oxygen. Generally where there is light, there is plenty of oxygen, mainly because of modern photosynthesizing organisms (capturing light and releasing gaseous oxygen, such as phytoplankton and plants).
