Scientists have uncovered a pair of 1.6 billion-year-old fossils, that appear to contain red algae, in uniquely well-preserved sedimentary rocks at Chitrakoot in central India.
These fossils could be the oldest plant-like life discovered on Earth.
Until now, the oldest known red algae was 1.2 billion years old, said the paper in the journal PLOS Biology.
Scientists often debate the question of when complex life began on Earth, but they generally agree that large multi-cellular organisms became common about 600 million years ago.
This discovery could lead experts to rewrite the tree of life, said lead author Stefan Bengtson, Professor Emeritus of palaeo-zoology at the Swedish Museum of Natural History.
The scientists found two kinds of fossils resembling red algae.
One type is thread-like, the other one consists of fleshy colonies.
The scientists were able to see distinct inner cell structures and so-called cell fountains, the bundles of packed and splaying filaments that form the body of the fleshy forms and are characteristic of red algae.
The earliest traces of life on Earth are at least 3.5 billion years old.
These single-celled organisms, unlike eukaryotes, lack nuclei and other organelles.
Large multi-cellular eukaryotic organisms became common much later, about 600 million years ago, near the transition to the Phanerozoic Era, the “time of visible life.”
Discoveries of early multi-cellular eukaryotes have been sporadic and difficult to interpret, challenging scientists trying to reconstruct and date the tree of life.
The oldest known red algae before the present discovery are 1.2 billion years old.
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.
The research group was able to look inside the algae with the help of synchrotron-based X-ray tomographic microscopy.