Some of the greatest moments in the history of biology slip from the world's memory, their anniversaries hardly noticed among the wars, bankruptcies and celebrity detoxifications. But before this month passes, let us stop to remember one of those great moments that came 30 years ago, in November 1977: the death knell of the animal kingdom.

The animal kingdom's decline came in the form of a three-page paper that appeared in the Proceedings of the National Academy of Sciences. Its lead author, Carl Woese, had spent the previous few years trying to find a way to figure out the relationship of all living things, including microbes. A taxonomist can classify a giraffe, a bat and a human as mammals simply by looking at them. They have hair, for example, and they nurse. But microbes are harder to make sense of. They might simply look like a rod or a sphere.