Clues to the origin of life in nearly 4 billion-year-old fossils

An international team of researchers has discovered traces of microorganisms dating back at least 3,770 million years, providing direct evidence of one of the oldest forms of life on Earth.

Haematite tubes from the NSB hydrothermal vent are evidence of the oldest microbial fossils and life on Earth. Photo: Matthew Dodd.

Tiny filaments and tubes formed by bacteria living on iron were found in quartzite layers in the Nuvvuagittuq Supracrustal Belt (NSB), Quebec, Canada, Phys.org reported on March 1.

The NSB contains some of the oldest sedimentary rocks on Earth, likely part of an iron-rich deep-sea hydrothermal vent system that provided habitat for the first life forms to emerge 3,770–4,300 million years ago.

"Our findings support the hypothesis that life emerged from hot hydrothermal vents on the seafloor shortly after Earth's formation. The rapid emergence of life on Earth is consistent with other evidence of 3,700 million-year-old sedimentary mounds shaped by microorganisms," said lead author Matthew Dodd, a PhD student at the University of California, Los Angeles.

The study, published yesterday in the journal Nature, describes the discovery and detailed analysis of the fossils. Prior to this discovery, the oldest microbial fossils found in Western Australia were 3.46 billion years old, but some scientists thought they might be non-biological artifacts on rocks.

Researchers have systematically considered how the filaments and tubes made of haematite, a form of iron oxide or rust, could form through non-biological means such as changes in temperature and pressure in the rock as the sediment is buried, but all possibilities are unlikely.

Haematite structures with the same characteristic iron-oxidizing bacterial clade commonly found near hydrothermal vents today occur alongside graphite and minerals such as apatite and carbonate associated with biological material including fossil bones and teeth.

The team also found that the fossils contained minerals with spherical structures contained in younger rocks, suggesting that haematite likely formed when bacteria oxidized iron for energy and fossilized it.

"This discovery indicates that life evolved on Earth at a time when Mars and Earth had liquid water on their surfaces, raising many interesting questions about extraterrestrial life. Therefore, we hope to find evidence of past life on Mars 4,000 million years ago. If not, Earth may be a special exception," Dodd concluded.

According to VNE