Animal-like embryos came before animals

Nov. 28 (UPI) -- Before the earliest animals diverged from their single-celled ancestors and diversified into a few dozen anatomical shapes, primitive organisms began experimenting with animal-like embryos.

New analysis of 609-million-year-old fossils recovered from China suggests animal-like embryological traits evolved before the emergence of the first animals.

The fossils represent Caveasphaera, a multicellular species. Upon finding the remains preserved in rock formations in South China's Guizhou Province, scientists couldn't decide whether the species should be classified as animal or non-animal.

Using X-ray microscopy, scientists were able to study the Caveasphaera fossils cell-by-cell. The different fossils revealed the organisms at various stages of development, some as single cells, others in multicellular forms.

"We were able to sort the fossils into growth stages, reconstructing the embryology of Caveasphaera," Kelly Vargas, researcher at the University of Bristol, said in a news release.

Researchers shared their analysis of the fossilized embryonic experiments this week in the journal Current Biology.

"Our results show that Caveasphaera sorted its cells during embryo development in just the same way as living animals, including humans," said Zongjun Yin of Nanjing Institute of Geology and Palaeontology of the Chinese Academy of Sciences. "[There is] no evidence that these embryos developed into more complex organisms."

Scientists still aren't sure whether Caveasphaera was an animal or not, but the latest analysis suggests the hard-to-classify species had evolved animal-like embryonic development -- the ability to produce different tissue layers and organs.