'Missing link' microbes may help explain how we evolved from single cells

Newly discovered microbes can explain evolution of animals from single-celled organisms.

Uppsala University scientists have discovered a "missing link" between the two main life-forms on earth that could help to explain the evolution of organisms with complex cells like those found in all animals including humans, the Independent reported.

Until now the division between the simple cells of microbes such as bacteria from the more complicated cells of animals and plants has been so abrupt and absolute that it was difficult to see how one could have evolved from the other.

However, researchers have now found a new microbial species that sits between the two branches of life, and which appears to be a living descendent of the last common ancestor of both the simple microbial life-forms and the complex life we see all around us.

Team leader Thijs Ettema said that they've identified an organism that seems to represent a very distant cousin of humans and in doing so it tells them something about their own dark past.

Ettema added that they are looking at the origin of complex life which occurred sometime after the origin of life itself. This discovery puts the origin of complex life in the spotlight.

It is believed that life on earth originated more than about 3.5bn years ago but about 2bn years ago it began to evolve into two broad branches, "prokaryotes" like the simple cells of bacteria and the "eukaryotes" with complex cells containing a nucleus and other intricate internal structures.

In the study, the researchers found a new organism with the genes of both groups. It was found in sediment samples retrieved from the seabed about 10km (6.2 miles) away from a volcanic hydrothermal vent called Loki's Castle situated in the mid-Atlantic between Greenland and Norway at a depth of 2,352 metres.

The study is published in the journal Nature.