A controversy around the possible discovery of the oldest life forms yet

Hematite tubes (Image courtesy Matthew Dodd, University College London)
Hematite tubes (Image courtesy Matthew Dodd, University College London)

An article published in the journal “Nature” describes what might be the oldest life forms discovered so far. An international team led by Matthew Dodd studied tiny filaments and tubes they think were formed by bacteria living on iron and were found in the layers of quartz in the Nuvvuagittuq Belt in Quebec, Canada. However, this research has already raised a controversy.

In August 2016 a research described the discovery of 3.7 billion years old fossil stromatolites but the Nuvvuagittuq Belt contains some of the oldest rocks on Earth. Over the years various dating with different methods were carried out and found that those rocks’s age is between 3.75 and 3.78 billion years. A 4.321 billion years dating raised many doubts. In any case, fossil life forms discoveries within those rocks would be the oldest discovered so far.

The authors of this new research sought to understand if the tubes and filaments could be generated through non-biological processes. They’re made of hematite, a form of iron oxide, and its structures have the characteristics ramifications of today’s iron-oxidising bacteria that can be found near hydrothermal sources. They were found together with graphite and minerals such as apatite and carbonates which may be found in biological materials such as bones and teeth and are often associated with fossils.

The researchers also discovered that the mineralized fossils are associated with spheroidal structures that usually contain fossils in less ancient rocks they think are the product of putrefaction and are mineralogically identical to other rocks that contain fossils. This suggests that the hematite likely formed when bacteria that oxidized iron to get energy got fossilized in the rock.

According to the researchers the set of data obtained from the tests of these tubes and filaments and of the structures associated with them prove that there was a biological activity in a submarine hydrothermal at least 3.770 billion years ago. However, this conclusion has been the subject of dispute soon after the article’s publication.

For example, Professor Martin Van Kranendonk, a world expert on microfossils and among the discoverers of the 3.7 billion year old fossil stromatolites, claims that the rocks where the structures were discovered are strongly recrystallized. This supports the thesis of Professor Malcolm Walter, one of the founders of the Australian Centre for Astrobiology, who claims that the rocks were altered at very high temperatures that destroyed the original structures.

Professor Franco Pirajno, one of the authors of the research, replied that the comparison with fossil stromatolites from 1.8 billion years ago at the Earaheedy Basin and from 3.5 billion years ago at the Pilbara Basin show exactly the same structures examined by him and the other researchers.

A dispute of this level can only lead to further studies of the structures discovered in Quebec. It’s one of the cases in which the difficulties in the analysis of very ancient rocks make the interpretations of results complex. Whatever the end result, this type of research pushes scientists to go beyond the existing limits in the field of paleontology developing their analytical techniques even more.

If the discovery is confirmed, the implications of such ancient life forms would be important: Matthew Dodd noted that at the time when they formed the conditions on Mars were similar to those on Earth so if life forms developed so soon on Earth it’s possible that this happened on Mars as well.

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