Here is a picture of two of the most famous hands in art history, and they go along with a not-very-famous but super important story about how human hands evolved.
“Nature does not invent very often completely from scratch,” writes evolutionary biologist Sean B. Carroll, “rather, it remodels its existing structures with took kit genes that are already available.” In terms of the progenitors of our hands, there were primordial limbs that developed into wings, antennae, legs, and claws in other animals.
What made a lot of these varied morpholgies possible were DNA “switchers” – part of the gennome’s non-gene “junk” DNA that either turn “on” or “off” a particular coding gene. We can get a sort of snapshot of what the switching DNA does with embryology. The progression of the human embryo often takes on the shapes of earlier phases of our evolution.
For instance, our modern hands have webbing in an embryonic state (see second photo). Thanks to some “switching” DNA, they lose this webbing in utero through programmed apoptosis– our DNA kills off the cells making up the webbing before we are born. Without the switching DNA, humans can have a mutation that causes webbing in between fingers and toes. I didn’t post a picture of that, and you are welcome.
Source(s): Sean Carroll, _Endless forms Most Beautiful_, p. 180 etc, Norton, 2005.
