Were We Sponges or Slime?

New research suggests that placozoans, amoeba-like, multicelled organisms, are ancestors to sea sponges, thought to be the most ancient ancestor of all animals, says a blog post at Discover magazine. In work published this week, scientists performed molecular phylogenetic analysis of animals from 24 taxa, generating a new tree of life that placed placozoans, sponges, and jellyfish on one line and more complex animals on another. While their work suggests that placozoans, and not sponges, were the original ancestors of all animals, critics argue that it's not exactly the case, since they are not directly related to the more complex Bilataria. Additionally, the methods used may have been flawed. "I am tired of these molecular papers that don't make sufficient controls to check the reliability of the phylogenetic inferences," says molecular phylogenist Hervé Phillippe in a story at Nature.