Geobiologist Shuhai Xiao of Virginia Tech and his colleagues suspect that these fossils might represent a transition from simple single-celled life to more complex multicellularity in the world's oceans 600 million years ago.
The cells in these matryoshka cluster are smaller than the cells in the rest of the fossil and appear to have been fossilized in the midst of dividing and growing. Xiao and his colleagues believe that these matryoshkas may be clusters of reproductive cells, segregated from the somatic, or body, cells of the organism.
The findings are consistent with some kinds of algae or early animal embryos. However, adult animals to produce these embryos have yet to be found.