Geologists find oldest evidence of life's mobility on Earth

Source: Xinhua| 2019-02-12 05:22:57|Editor: yan
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WASHINGTON, Feb. 11 (Xinhua) -- An international team led by French geologists uncovered the oldest fossilized traces of life's ability to move, tracing back to 2.1 billion years ago.

The study published on Monday in the Proceedings of the National Academy of Sciences showed that certain multicellular organisms in a primitive marine ecosystem in a fossil deposit in Gabon were sophisticated enough to move through its mud, rich in organic matter.

Located in Africa's Franceville Basin, the deposit produced the oldest existing fossils of multicellular organisms that could move, which was more than 1.5 billion years earlier than previously thought.

The previous remnants were dated to 570 million years ago, an estimate that appeared to be confirmed by the molecular clock, according to the study.

The researchers used a non-destructive imaging technique called X-ray computed micro-tomography to analyzed the fossil, and found a tubular structures, with generally consistent diameter of a few millimeters, running through fine layers of sedimentary rock.

Geometrical and chemical analysis revealed that they were biological in origin and appeared at the same time the sediment was deposited.

The traces are located next to fossilized microbial biofilms, and those biofilms formed carpets between the superficial sedimentary layers.

The researchers suggested that the organisms moved in search of nutritive elements and the dioxygen, both produced by cyanobacteria.

They showed that this biodiversity co-occurred with a peak in dioxygenation of the atmosphere, and developed in a calm and shallow marine environment.

It is known that aerobic life has evolved from single-celled bacteria species to complex eukaryotic organisms, depending on the oxidizing power of dioxygen in some metabolic pathways.

The scientists could not describe the exact shape of those living elements, but they speculated that they might be similar to colonial amoebae, clustering together to form a type of slug to forage food when resources become scarce.

The evidence of mobility found in rock that is 2.1 billion years old raised new questions about the history of life, according to the study.

They wondered whether this biological innovation a prelude to more perfected forms of movement, or an experiment cut short by the drastic drop in atmospheric oxygen occurring about 2.08 billion years ago.