ORIGINS Animal Eve: Sponges

photo of sponges
Origins: Animal Eve, a newly revised chapter from The Shape of Life book, is a comprehensive resource on sponges.

For most of human history we weren’t even sure that sponges were animals. Two thousand years ago, they were listed among Aristotle’s ‘Intermediates,’ somewhere between plants and animals. His confusion is understandable to anyone who has ever seen, but not looked too closely at a sponge, which has no head, no brain, no bones, no mouth, and no internal organs. Sponges come in an astonishing variety of shapes that to us look like cups, fans, tubes and colorful, crusty smears on rocks and coral. They range in size from a few millimeters wide to more than a meter tall, like the great barrel-like glass sponge that lives in Antarctic waters. All sponges are aquatic, tied permanently to the water by their lifestyle and body plan. Of the 10,000 species alive today, only 150 live in fresh water, the rest in the ocean. Read the full chapter...