The Shape of Life . Origins

What was the first animal? How do we know? (Barrel sponge pumping)

For the first time ever, scientists believe they have gathered substantial evidence that points to a single animal group of creatures that gave rise to all animals, including humans. Researchers such as Cristina Diaz and Mitch Sogin think that the most likely candidate for this "Animal Eve" is a group of creatures that still exist: the sponges.

Sponges, members of the phylum Porifera, are considered the oldest living animal phylum. The name Porifera means "pore bearer" in Latin. Sponges are the only animals that if broken down to the level of their cells can miraculously reassemble and resurrect themselves. These seemingly inanimate creatures are also fantastic pumps, filtering tons of water to harvest just a few ounces of microscopic food.

How do we know sponges were our ancestors? It turns out that all organisms in their genes carry clues to their evolutionary history -- a unique set of acquired genetic changes passed on through countless generations. This fact allowed Mitch Sogin to compare and contrast specific sets of genetic differences between sponges, flies, fish, frogs, humans and other organisms. He discovered that sponges, indeed, were the start of the animal kingdom and laid the foundation for all animals to follow.

Searching for the First Animal Biologist Cristina Diaz studies sponges in the waters off Indonesia. How do sponges pump water? How do we know they're really animals?		Finding Proof of the First Animal Molecular biologist Mitch Sogin uses DNA sequencing to prove that we're all descendants of the sponge.

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