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.
These specimens were discovered and studied by an international multidisciplinary team of researchers coordinated by Abderrazak El Albani of the Laboratoire “Hydrogéologie, Argiles, Sols et Altérations”. Their work, due to be published in Nature on 1st July, will feature on the cover of the journal.
The first traces of life appeared in the form of prokaryotic organisms, in other words organisms without a nucleus, around three and a half billion years ago. Another major event in the history of life, the “Cambrian explosion” some 600 million years ago, marked a proliferation in the number of living species. It was accompanied by a sudden rise in oxygen concentration in the atmosphere. What happened between 3.5 billion and 600 million years ago though?
Scientists have very little information about this era, known as the Proterozoic. Yet, it is during this crucial period that life diversified: to the prokaryotes were added the eukaryotes, single or multicelled organisms endowed with a more complex organization and metabolism. These large-sized living beings differ from prokaryotes by the presence of cells possessing a nucleus containing DNA.
While studying the paleo-environment of a fossil-bearing site situated near Franceville in Gabon in 2008, El Albani and his team unexpectedly discovered perfectly preserved fossil remains in the 2.1 billion-year-old sediments. They have collected more than 250 fossils to date, of which one hundred or so have been studied in detail. Their morphology cannot be explained by purely chemical or physical mechanisms.
These specimens, which have various shapes and can reach 10 to 12 centimeters, are too big and too complex to be single-celled prokaryotes or eukaryotes. This establishes that different life forms co-existed at the start of the Proterozoic, as the specimens are well and truly fossilized living material..!
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.