In 1969, in an attempt to bring some order to the growing inadequacies of classification, an ecologist from Cornell University named R. H. Whittaker unveiled in the journalScience a proposal to divide life into five principal branches—kingdoms, as they are known—called Animalia, Plantae, Fungi, Protista, and Monera. Protista, was a modification of an earlier term, Protoctista, which had been suggested a century earlier by a Scottish biologist named John Hogg, and was meant to describe any organisms that were neither plant nor animal.

Though Whittaker's new scheme was a great improvement, Protista remained ill defined. Some taxonomists reserved it for large unicellular organisms—the eukaryotes—but others treated it as the kind of odd sock drawer of biology, putting into it anything that didn't fit anywhere else. It included (depending on which text you consulted) slime molds, amoebas, and even seaweed, among much else. By one calculation it contained as many as 200,000 different species of organism all told. That's a lot of odd socks.