Scientists stumble on complex life form

LONDON - 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 organised 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 multi-disciplinary team of researchers led by Abderrazak El Albani of the Laboratoire “Hydrogéologie, Argiles, Sols et Altérations” (CNRS/Université de Poitiers), Paris.

The first traces of life appeared in the form of prokaryotic organisms or organisms without a nucleus, around three-and-a-half billion years ago.

Another major event in the history of life, 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 organisation 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 100 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 centimetres, are too big and too complex to be single-celled prokaryotes or eukaryotes, said a CNRS release.

This establishes that different life forms co-existed at the start of the Proterozoic period, as the specimens are well and truly fossilised living material.

These findings featured on the covers of the Thursday edtion of Nature.