Mystery of how life evolved in oceans has been solved

1 Dec 2015

A missing link between the evolution of our planet, its formation of water and how life evolved in it has, after decades of mystery, been solved, and it’s all down to one very, very small microbe.

When it comes to how life evolved in oceans, there has been a number of known facts, with scientific understanding saying that the Earth’s oceans only became oxygenated 800m years ago when two-thirds of these oceans were colonised by the microorganism phytoplankton.

The sheer number of these microorganisms helped fill oceans with the oxygen necessary to spur on the life that has led to almost all animals living on Earth today, but it was not the first microorganism to produce oxygen.

Herein lied the mystery for scientists, who could not figure out why a more ancient microorganism known as cyanobacteria that existed 2,700m years ago that produced oxygen through photosynthesis did not lead to the creation of life on a grander scale?

Without this, our planet would be lifeless

Led by Dr Patricia Sánchez-Baracaldo from the School of Geographical Sciences at the University of Bristol, a team of researchers says the answer lies in cyanobacteria’s affinity with being a landlubber, or at least a near-land-lubber.

Publishing the findings in Scientific Reports, the team traced back the origins of the cyanobacteria to developing first in freshwater habitats like rivers, lakes and coastal inlets for millions of years, before moving into oceans where they only then began to thrive.

“By producing oxygen in vast quantities,” Dr Sánchez-Baracaldo said, “these cyanobacteria enabled the development of complex life in our oceans. These biological events are linked – they help explain why it took so long for complex life to evolve on our planet. Cyanobacteria needed to colonise the oceans first.

“The genomic revolution has hugely improved our understanding of the tree of life of cyanobacteria. Without cyanobacteria, complex life on our planet as we know it simply would not have happened.”

Bacterial bloom in water image via Shutterstock

Colm Gorey was a senior journalist with Silicon Republic