Darwin's principle of natural selection leads to the prediction that the proper way to analyze any evolutionary development is to see the new features as adaptive to environments. And that's a perfectly good principle. The problem is that there are many evolutionary biologists who view everything that happens in evolution as directly evolved for adaptive benefit. And that just doesn't work. Whenever you build a structure for adaptive reasons, the structure is going to exhibit properties that have nothing to do with adaptation. They're just side consequences.

The world, unfortunately, rarely matches our hopes and consistently refuses to behave in a reasonable manner.

It is the things we think we know - because they are so elementary or because they surround us - that often present the greatest difficulties when we are actually challenged to explain them.

Taxonomy (the science of classification) is often undervalued as a glorified form of filing-with each species in its folder, like a stamp in its prescribed place in an album; but taxonomy is a fundamental and dynamic science, dedicated to exploring the causes of relationships and similarities among organisms. Classifications are theories about the basis of natural order, not dull catalogues compiled only to avoid chaos.

I was lucky to wander into evolutionary theory, one of the most exciting and important of all scientific fields. I had never heard of it when I started at a rather tender age; I was simply awed by dinosaurs. I thought paleontologists spent their lives digging up bones and putting them together, never venturing beyond the momentous issue of what connects to what. Then I discovered evolutionary theory. Ever since then, the duality of natural history-richness in particularities and potential union in underlying explanation-has propelled me.

I like to summarize what I regard as the pedestal-smashing messages of Darwin's revolution in the following statement, which might be chanted several times a day, like a Hare Krishna mantra, to encourage penetration into the soul: Humans are not the end result of predictable evolutionary progress, but rather a fortuitous cosmic afterthought.

Biological determinism is, in its essence, a theory of limits. It takes the current status of groups as a measure of where they should and must be ... We inhabit a world of human differences and predilections, but the extrapolation of these facts to theories of rigid limits is ideology.