Sponges are an ancient group, with fossils dating back at least 650 million years. They are thought to have been the first group of animals to branch from all the others. Therefore, genes shared by sponges and other animals must have been present in the common ancestor of all metazoans. This ancestor would have evolved mechanisms to coordinate cell division, growth, specialization, adhesion and death; this suggests that early sponges already had a developmental set of tools similar to those in metazoans today, said Putnam, an assistant professor of ecology and evolutionary biology.
Read more on Astrobiology magazine