What was the first animal: The jelly or the sponge?

Comb Jelly

That depends on whose phylogenetic research you support.

Two papers published in April 2017, one in Current Biology and the other in Nature Ecology & Evolution, argued to have resolved this issue, but each papers conclusions pointed to different animals, the sponge and the comb jelly repetitively.  

How did they come to two different conclusion? They both used different genomic data sets and phylogenetic approaches.

The Current Biology paper by Simion colleagues used a huge genetic dataset of 1,719 taxas to determine the sponge is the oldest animal. While the Nature Ecology & Evolution by Shen and colleagues focused their research on “contentious relationships”, which is significantly smaller dataset, to claim the comb jelly as the earliest animal.

Sponge

Theses two papers highlight the difficulty of phylogenetic reconstruction even with large genomic data employed.

I would also like to point out that of theses two studies the Nature paper received more news coverage.

For more review see the Smithsonian Magazine article on these two papers.

-Kristen Tuosto