Where are multicellular organisms found

Evidence of early animal lineage discovered

Blacksburg - In the geological epoch of the Cambrian, about 541 to 485 million years ago, a development took place that researchers, without exaggeration, describe as a species explosion. The first representatives of almost all of today's animal phyla emerged within a few million years.

Before that, comparatively simple unicellular microorganisms populated the earth, especially cyanobacteria. When and how exactly the transition from unicellular to multicellular life took place and ultimately led to the Cambrian species explosion is one of the great puzzles in evolutionary history. The attempted explanations are almost as numerous as the fossil finds of earlier living things.

Functions of higher life forms

Researchers led by geobiologist Shuhai Xiao from the Virginia Polytechnic Institute in Blacksburg are shedding new light on this old question with a discovery: In the journal "Nature" they describe extremely well-preserved fossils that could represent the earliest lineage of multicellular animal life.

The finds from the southern Chinese Doushantuo Formation date from around 60 million years before the beginning of the Cambrian explosion, from the Ediacarian period. According to the researchers, the 600 million year old remains are embryos shortly after the first steps in cell division. They would show signs of cell differentiation in germ and body cells and programmed cell death, properties that would be clear indications of early multicellular organisms.

New hypotheses

The fossils are so well preserved that they can be identified as so-called Ediacara organisms and thus dated, according to the researchers. Similar fossils have already been found in the past, but so far mostly interpreted as bacteria, unicellular eukaryotes, algae or early stages of the ancestors of modern animals.

If the assumptions of Xiao and colleagues are confirmed and the finds actually belong to the earliest lineage of animal life, some previous assumptions about the origin of multicellular life on earth must be rejected. (dare, derStandard.at, 25.9.2015)