Abstract
For several years, paleontologist Douglas Erwin of the National Museum of Natural History in Washington, D.C., has been quietly challenging a central tenet of Neodarwinism: that the biological present is the key to the evolutionary past. The idea is that processes observed today provide analogues to the processes by which life evolved in the past--or, as geneticist Theodore Dobzhansky put it, that a "sign of equality" obtains between "the mechanisms of macro- and micro-evolution" (Genetics and the Origin of Species, 1937, p. 12). Dobzhansky qualified that statement, however, by noting that the equality of micro- and macroevolution could be established only as a "working hypothesis." Today, more than 60 years later, Erwin argues that the unknown processes that brought about the origin of the animal body plans (i.e., the major architectural features distinguishing different kinds of animals), whatever those processes may be, are ones for which we have no modern analogues. For "the simple, empirical fact is that the establishment of new body plans is not a frequent event" (p. 626). Thus Dobzhansky's working hypothesis has been proved false.