Evolution of the human hand

NPR played a really cool story this morning on the evolution of the human hand. As we know, the human thumb is one of our greatest evolutionary boons. James Noonan at Yale has been doing comparative genetics - he looks at the sequences in humans, mice, chickens, dogs, and chimps - and sees if there have been sequences that have been evolutionary stable over evolutionary time in some species and whether that same location has mutated in humans. I think it's evolved so that we can raise our horns, but that's neither here nor there.

It's sort of like comparing musical themes. A whole bunch of people can know "Twinkle, twinkle little star" and in one person, you might find that they have embellished it - essentially written a variation on the theme by, perhaps, ornamenting it trills or other embellishments, adding a chordal harmony to it, or adding counterpoint. You can still trace the tune back to the original by Mozart.

And so Noonan found a regulatory element that was odd, injected it into a mouse egg, and discovered that the mouse embryo spouted a thumb where a mouse would have a thumb. Over the course of evolution, this gene came to regulate when, where, and how the thumb's bones, tendons, and muscles develop. Chalk one more up for evolutionary biology discovering more about what makes us human.

I haven't seen anything else on it circulating this morning at New Scientist, Science Daily, or Eurekalert.