Re Darwin’s finches not a good example of Darwinian evolution? (Because they are so heavily hybridized): David A. DeWitt writes to say:
When considering the ‘evolution’ of the finches, we also need to take into account hidden genes. These are genes that, while present in the population, are not linked to an observed phenotype. For example, I crossed a brown mouse and a white mouse and the offspring were all grey. When the grey mice were crossed, the next generation included mice that were white, brown, white with brown spots, white with grey spots, a grey/brown mix, and one that was yellow. All of these varieties were derived from the same ancestral pair, yet all of these coat color traits were hidden and only showed up in successive rounds of inbreeding and within 2 generations. There were no mutations, just different combinations of genes.
The same thing is likely happening with finches, with Ensatina salamanders, Hawaiian honeycreepers and a variety of other populations of organisms.
See the issue is some genes will mask the expression of others. Two of my daughters have red hair, but my wife and I both have brown hair. That means we both have genes for red hair but you can’t tell. If we married other people, we would be passing on genes for red hair in the population, but you couldn’t tell unless our children happened to marry and then voila: red hair.
So what might look like evolution (change in gene frequency over time) may simply be fluctuation in the expressed genes that are part of the variation in the population from the beginning.
It strikes a layperson that a variety of genetic patterns that do not display in a given generation could help account for the tenacity of life forms such as the mouse—in a world where thousands of species are on the endangered list. But not mice. Never mice. (Never rats either, worse luck.)
Readers may remember neuroscientist deWitt from: Contemplating Bill Nye’s 51 skulls slide, where the discoveries mad in Nye’s absence are more informative than those made in his presence.
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