Discovery prompts evolutionary history rethink

The discovery of fossilised algae suggests that advanced multicellular life evolved much earlier than previously thought.

Scientists from the Swedish Museum of Natural History have found 1.6bn year old fossils of red algae, a multicellular eukaryotic organism, in well-preserved sedimentary rocks in Chitrakoot, central India. The researchers observed distinct inner cell structures and cell fountains – bundles of packed and splaying filaments that are characteristic of the algae.

Stefan Bengtson, Professor emeritus at the Museum, said: “You cannot be a hundred per cent sure about material this ancient, as there is no DNA remaining, but the characters agree quite well with the morphology and structure of red algae”.

The earliest traces of life are single celled organisms at least 3.5bn years old, which lack nuclei and other organelles. Larger multicellular eukaryotes were not common until about 541m years ago at the beginning of the Phanerozoic Era, also known as the ‘time of visible life’.

However, while earlier discoveries of these early multicellular eukaryotes have been made, they have proven difficult to interpret – meaning dating the tree of life has been a challenge. For example, the oldest known red algae – before the present discovery – are 1.2 billion years old. Now, The Indian fossils, 400 million years older and by far the oldest plant-like fossils ever found, suggest that the early branches of the tree of life need to be recalibrated.

Professor Bengtson said: “The 'time of visible life' seems to have begun much earlier than we thought.” The fossils thought to be red algae lies embedded in layered sheets of cyanobacteria, called stromatolites and were discovered using synchrotron-based X-ray tomographic microscopy.

The study was published in PLOS Biology.