New research analysing huge amounts of data suggests that the comb jelly split off from sponges before other multicellular organsisms and went on to develop a nervous system independently of other animals.
(Image from University of California Museum of Paleontology)
You can read about it at Science Daily:
This finding challenges the traditional view of the base of the tree of life, which honored the lowly sponge as the earliest diverging animal. “This was a complete shocker,” says Dunn [no first name given]. “So shocking that we initially thought something had gone very wrong.”
But even 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 tissueless, nerveless sponge.
The presence of the relatively complex comb jelly at the base of the tree of life suggests that the first animal was probably more complex than previously believed, says Dunn.
While cautioning that additional studies should be conducted to corroborate his team’s findings, Dunn says that the comb jelly could only have achieved its apparent seniority over the simpler sponge via one of two new evolutionary scenarios:
- the comb jelly evolved its complexity independently of other animals, after it branched off onto its own evolutionary path; or
- the sponge evolved its simple form from more complex creatures — a possibility that underscores the fact that “evolution is not necessarily just a march towards increased complexity,” says Dunn. “This scenario would provide a particularly dramatic example of that principle.”
For earlier research on the origin of the nervous system, see “Nervous system originated in sponges.”