Small changes in the relative timing and rates of growth of an animal’s parts — a concept called heterochrony — can make an enormous difference in the adult animal’s morphology. For instance, crabs and lobsters are built of essentially the same parts, but in the development of a crab the carapace broadens quickly, while the abdomen grows slowly, while in the lobster the timing is reversed. These differences may require only tiny changes in the genome, but can have big results. A similar source of variation is neoteny, which is the retention of juvenile features in the adult. (Indeed, we modern humans are a good example of that, with our big heads, small jaws, and hairless bodies.)
It seems clearer and clearer that much of the diversity in the living world is due to little variations in important rules, and to tiny adjustments of powerful control systems. Now a group of researchers at Harvard have advanced our understanding by teasing out, from a study of — what else? — Darwin’s-finch beaks, a powerful mathematical generalization of morphological variation, with only three parameters.
Here.
One Comment
Truly blind-mowing. As for this:
“Indeed, we modern humans are a good example of that, with our big heads, small jaws, and hairless bodies.”
Hairless bodies? Speak for yourself, sir.
Kevin