[C]ontingency is a thing unto itself, not the titration of determinism by randomness. - Stephen Jay Gould

It's his last book. He wrote in in 1881, the year before he died, and usually we expect that in old age, just before death, that a great scientist will write a pontificating philosophical treatise on the nature of reality. And Darwin... wrote a book on worms. ...He was interested in worms because they were... a metaphor for his larger world-view. The worms that slowly churn the topsoil of England... that work literally beneath our feet, that we never notice, that we think are insignificant because they're so small and lowly, are in fact producing the very soil that is the basis of agriculture. And therefore Darwin uses it as a metaphor for the importance of apparently tiny things when you extend them over long periods of time. And that's what evolution is, the extension of small change (to Darwin) over vast periods of time. So the worms become a metaphor for evolution and for the whole process of temporal change, a very fascinating book.

We do not inhabit a perfected world where natural selection ruthlessly scrutinizes all organic structures and then molds them for optimal utility. Organisms inherit a body form and a style of embryonic development; these impose constraints upon future change and adaptation. In many cases, evolutionary pathways reflect inherited patterns more than current environmental demands. These inheritances constrain, but they also provide opportunity. A potentially minor genetic change […] entails a host of complex, nonadaptive consequences. The primary flexibility of evolution may arise from nonadaptive by-products that occasionally permit organisms to strike out in new and unpredictable directions. What “play” would evolution have if each structure were built for a restricted purpose and could be used for nothing else? How could humans learn to write if our brain had not evolved for hunting, social cohesion, or whatever, and could not transcend the adaptive boundaries of its original purpose?

I do not see why we should reject all genetic engineering because its technology might, one day, permit such a perversion of decency in the hands of some latter-day Hitler—you may as well outlaw printing because the same machine that composes Shakespeare can also set Mein Kampf. The domino theory does not apply to all human achievements. If we could, by transplanting a bacterial gene, confer disease or cold resistance upon an important crop plant, should we not do so in a world were people suffer so terribly from malnutrition? Must such a benefit imply that, tomorrow, corn and wheat, sea horses and orchids will be thrown into a gigantic vat, torn apart into genetic units, and reassembled into rows of identical human servants? Eternal vigilance, to recombine some phrases, is the price of technological achievement.