Sponge Genes Provide Toolkit for Multicellular Life

Read more about me, the humble sponge!

Sponges are primitive creatures with a body plan unlike that of any other living organism. They are also our most distant animal cousins. Now that their genetic make-up has finally been sequenced, it could explain one of the greatest mysteries of evolution: how single-celled organisms in the primordial oceans evolved into complex multicellular animals with the spectacular diversity of body plans we see today.

The sponge genome confirms that sponges share much the same genetic tool kit for multicellularity as the rest of the animal kingdom. This means that all the key genetic prerequisites for modern animals made up of trillions of cells were in place well before sponges split from other animals 600 million years ago. What's more, the sponge genome reveals the very ancient origin of genes involved in cancer, which is caused by a derailing of cell replication and is the signature disease of multicellularity.

We had already gained some insights from studies comparing the genomes of single-celled protozoans with those of other primitive animals. But there was a crucial gap, occupied by the sponges. "Sponges really were the last missing piece of this puzzle," says Mansi Srivastava, an evolutionary biologist at the Whitehead Institute in Cambridge, Massachusetts.

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