Darwin's Doubt: The Explosive Origin of Animal Life and the Case for Intelligent Design

by Stephen C. Meyer

The logic of these distinct body designs precludes sharing both anatomical characteristics. For this reason, any hypothetical bilaterian common ancestor could only have existed as a kind of lowest anatomical common denominator, or what evolutionary biologists call a “ground plan,” having only those few features that are common to all of the animal forms that allegedly evolved from it. But this creates a dilemma. If a fossilized form is simple enough to qualify as the common ancestor of later highly differentiated bilaterian phyla, then it will necessarily lack most of the important distinguishing anatomical features of those specific phyla. That means that all the interesting anatomical novelties that differentiate one phylum from another must arise along the separate lineages branching out from the alleged common ancestor well after its origin in the fossil record. Heads, jointed limbs, compound eyes, guts, anuses, antennae, notochords, stereoms, lophophores (a tentacled feeding organ), and numerous other distinguishing characteristics of many different animals must come later on many distinct lines of descent. Yet the gradual evolutionary origin of these characteristics is not documented in the Precambrian fossil record. These characteristics do not appear until they arise suddenly in the Cambrian explosion. For this reason, indistinct fossils such as Vernanimalcula—even if we take them as representing a common ancestor of many bilaterians—document little of the Darwinia...