Bald Monstrosity

Olivia Judson's latest New York Times column/blog called The Wild Side talks about "hopeful monsters."

The term was introduced in the 1930s by a geneticist called Richard Goldschmidt. He was interested in the question of how radical changes in morphology evolve.
As an example of radical change, he gave flatfish — the flounder and its relations. These are descended from fish with the usual fishy symmetry: the same left-right symmetry that we have. Larval flounders have it, too. But as adults, flounders have a profound asymmetry — one side has been completely flattened. What’s more, they have deformed, twisted skulls, and an eye that has migrated from one side of the face to the other. It’s as though you had both eyes on the same side of your nose. How did they get this way?
Goldschmidt speculated that big changes like this could be caused in one step by a mutation acting on the developing embryo. Most such mutations, he suggested, would produce individuals that were plain monstrous, and doomed to die without issue. But every so often, one of these mutations would happen in an environment where it could be beneficial. Then, the individual sporting it would be a hopeful monster, because it might have an evolutionary future as the founder of a new lineage.

The idea came into disrepute because the probabilities didn't look right, and the steps looked to big. Evolutionary development had to be gradual, it was thought.

Judson wants a revival, and her starting point is the featherless head of the vulture. She is inspired to her view by the fact that there seems to be a point mutation of chickens that produces a featherless head.

She mentions some other examples, including some that are well-known to evo-devo, but not perhaps to her. In particular she talks about the classic case of the flatfishes, which, it happens, were very nicely discussed in some detail by PZ Myers, evidently taking a brief break from his frothings on religion.

It's an interesting topic, and an interesting blog, though I would like to have seen a more detailed discussion of the evo-devo, and especially, some mention of the critical role of genetic switches. Go to PZ for that.