The series of mysterious spherical fossils were found in the Doushantuo Formation of southern China. Originally, researchers had believed them to simply be the remnants of bacteria or single-celled protists but this theory is becoming less viable since their discovery in 1998 after researchers began treating them differently, namely slicing them ultra-thin for examination.
New way of looking at these fossils
“The real value of these fossils is that we now have some direct evidence about how this transition from single-celled organisms to things like animals and plants occurred in the evolutionary past,” said study researcher Shuhai Xiao, a geobiologist at Virginia Tech in Blacksburg.
The fossils measure just 0.03 inches across and researchers believe they likely came from a shallow marine environment. The bizarre fossils, are known as Megasphaera.
Once researchers sliced the fossils they were able to shine light through them in order to see structures that hadn’t seen before. The then used microscopy and by so doing observed multiple cells in round clusters. The cells were both differently shaped and of different sizes suggesting different cellular functions. As a result of this treatment of the samples, it’s know believed that these are possible signs of very early plant life or ancient animal embryos.
Algae or animals?
“That is a telling sign of the complexity of multicellular organisms that you don’t find in bacteria or protists,” said Xiao.
“The bottom line is that they are multicelled and that they have cellular differentiation and that they have separation of reproductive cells from sterile somatic [body] cells,” Xiao said. “This is a big thing, because if you look at modern multicellular organisms, including animals, this is a critical step towards very complex multicellular organisms.”
The finding, however, is no guarantee of early animal life as the fossils’ anatomy is also reminiscent of algal life forms.
“We will have to be open-minded in terms of what can be expected,” Xiao said. “From the living animal point of view, we only have a certain morphology to go with. But there are extinct animals or even offshoots of the lineages leading to animals that could be rather different from what we know as animals living today.”