A new study mapping the evolutionary history of animals indicates that Earth’s first animal – a mysterious creature whose characteristics can only be inferred from fossils and studies of living animals – was probably significantly more complex than previously believed.
The study, funded by the National Science Foundation in the US, was the cover story of the April issue of . Using new high-powered technologies for analysing massive volumes of genetic data, the study defined the earliest splits at the base of the animal tree of life. The tree of life is a hierarchical representation of the evolutionary relationships between species that was introduced by Charles Darwin.
Among the study’s surprising findings is that the comb jelly split off from other animals and diverged on to its own evolutionary path before the sponge. This finding challenges the traditional view of the base of the tree of life, which honoured the lowly sponge as the earliest diverging animal. “This was a complete shocker,” says Casey Dunn of Brown University. “So shocking that we initially thought something had gone very wrong.”
But after Dunn’s team checked and rechecked their results and added more data to their study, their results still suggested that the comb jelly, which has tissues and a nervous system, split off from other animals before the tissue-less, nerve-less sponge.