Take the spine. It would make more sense, and spare us much Advil, if we had
four cross-braced columns of vertebrae instead of a single vulnerable one. Or the retina: it faces the back of the head rather than the front, burdening us with a blind spot where a clump of wiring gets in the way. We’re a collection of patches and fixes, held together with the biological equivalent of duct tape — the handiwork not of an intelligent designer but of the rough-and-ready processes of evolution.
Evolution “kluges” its solutions because it has only the crudest tools at its disposal: genetic mutations and millions of years. Natural selection can select only from what genetic accidents have made available, and the features it chooses may remain in place not because they are optimal, Marcus writes, but “because evolution just didn’t find a better way.”