Nov/Dec 2004 The Science Pages Features

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Simon Conway Morris is a distinguished scientist with a professorship in evolutionary paleobiology at Cambridge University. In Life's Solution, he enters the debate on the direction of evolution. Is it indeed a random affair that might well have turned out differently, as many orthodox Darwinians argue, or was the emergence of intelligent, self-reflective beings built into the process from the start? Conway Morris' answer is suggested by his subtitle: "Inevitable Humans in a Lonely Universe."

The central theme of Life's Solution is biological convergence. "Convergence" here refers to a counterintuitive result from evolutionary biology. When organisms share some feature, the first impulse of evolutionary biologists is to attribute the similarity to evolution from a common ancestor. Similarity is thus explained as a common inheritance.

Not every feature of biological similarity, however, can be attributed to descent from a common evolutionary ancestor. Indeed, biologists have shown that organisms can share a feature of similarity and yet have no common ancestor that exhibited that feature. This means that in the evolution of organisms sharing such a feature, the feature had to be reinvented separately on a number of occasions. This is biological convergence, and Conway Morris documents many fascinating examples of it (in addition to a general index, Life's Solution includes a five-page, double-columned index devoted strictly to convergences).

Biological convergence becomes downright astonishing when the similarity verges on identity. One of the best-known examples of striking convergence is the evolution of the camera-eye in vertebrates and cephalopods (e.g., human and octopus eyes respectively). These eyes are highly complex ...