Today, the journal Nature printed a remarkable letter reporting the discovery in Gabon, in western Africa, of a substantial number of specimens of complex multicellular life forms more than two billion years old. (The abstract for the letter appears here.)
If confirmed, as now appears likely, the find will represent the oldest known fossil remains of multicellular life forms, preceding the familiar “Cambrian explosion” of complex life forms by nearly one-and-a-half billion years, and the previous oldest known such specimens by some 200 million years.
The discovery is described in some detail in a press release ”Discovery of a Complex Multicellular Life From Over Two Billion Years Ago” on the website of the French Centre National de la Recherche Scientifique:
“The discovery in Gabon of more than 250 fossils in an excellent state of conservation has provided proof, for the first time, of the existence of multicellular organisms 2.1 billion years ago. This finding represents a major breakthrough: until now, the first complex life forms (made up of several cells) dated from around 600 million years ago. These new fossils, of various shapes and sizes, imply that the origin of organized life is a lot older than is generally admitted, thus challenging current knowledge on the beginning of life.”
As the authors of the release further indicate, “by studying the sedimentary structures of this site, which is remarkable both for its richness and quality of conservation, the scientists have shown that these organisms lived in a shallow marine environment (20 to 30 meters), often calm but periodically subjected to the combined influence of tides, waves and storms. In order to be able to develop 2.1 billion years ago and become differentiated to a degree never attained previously, the authors suggest that these life forms probably benefited from the significant but temporary increase in oxygen concentration in the atmosphere, which occurred between 2.45 and 2 billion years ago. Then, 1.9 billion years ago, the level of oxygen in the atmosphere fell suddenly.
“Until now, it has been assumed that organized multicellular life appeared around 0.6 billion years ago and that before then the Earth was mainly populated by microbes (viruses, bacteria, parasites, etc.). This new discovery moves the cursor of the origin of multicellular life back by 1.5 billion years and reveals that cells had begun to cooperate with each other to form more complex and larger structures than single-celled organisms. Several research avenues now need to be explored: understanding the history of the Gabonese basin and why the necessary conditions were gathered to enable this organized and complex life to exist; further exploring the site to enhance the collection of fossils; but also comparing the history of the Earth’s oxygenation with the mineralization of clays. The most urgent task, however, remains the protection of this exceptional site.”
For further information concerning this important discovery, see the very brief Fossilized Cell Blobs Could Be Oldest Multicellular Life in New Scientist, this slightly longer discussion in Discover which emphasizes the implication that “multicellular life could be nearly half as old as the Earth itself,” this good summary in The Scientist, and “‘Cookie-Shaped’ Fossils Point To Multicellular Life” in the BBC News.