Fossils dating back 2.1 billion years and having all the characteristics of multicellular organisms. This was discovered by an international team Abderrazak El Albani hydrase Laboratory ( CNRS -University of Poitiers ), in a clay quarry exploited black Franceville in the south – eastern Gabon.

Around 250 fossils of 10-120 mm long, were excavated. All are made of pyrite , ie iron disulfide (FeS₂ ) . This composition is consistent with a process of fossilization in an environment rich in iron , produced by bacteria derive their energy from sulfate reduction. The analysis of isotopes of carbon and sulfur showed that the samples represented an entity of organic origin in the sediment. Above all , the microtomography ( CT ) at high resolution highlighted in different specimens developed an internal organization . This center features more high pyrite around which lamellae which appear to have been fairly flexible . But this type of structure has never been observed for mineral occurrences , including the internal appearance is quite regular and uniform.

According to the researchers , these multicellular organisms lived in the sea at 20 or 30 meters deep . They breathed oxygen . Indeed, the low iron content of reactive sediments suggests that they are deposited in a hydrogen peroxide, which is consistent with the fact that, at this time oxygen concentration increased already since 300 million years . Oxygen, a new energy source , would facilitate cell growth and the large size of aerobic organisms.

Was it bacterial colonies or eukaryotic multicellular organisms , the cells with a nucleus containing the DNA ? ” It is likely that bacterial colonies can be fossilized in the natural environmentSays A. El Albani. We do not know of any other colony in the Precambrian fossil bacteria . These organisms were most certainly eukaryotes . ” Another argument in this sense , researchers have found sterol derivatives , the steranes in the sediment. Now they are regarded as biomarkers of eukaryotes .

Fossils of Franceville , dated from a period called the Precambrian Paleoproterozoic thus represent the ancestors of eukaryotic multicellular organisms whose diversity has “exploded “with the first animals , or metazoans , the Neoproterozoic to the late Precambrian and Cambrian , That 600-500000000 years .