Submitted by AmTheHobo t3_1175pzi in askscience
CharlesOSmith t1_j9a8geg wrote
When an organism is adapted to its environment, and the environmental pressures are not changing, there will appear to be very little evolution going on. In actuality, the alleles of genes will continue to mix and recombine in new ways during sexual reproduction which means that with each new generation the organism is still putting out new versions of itself.
The DNA polymerase is also hardwired with a certain error rate which is very low, but just high enough to allow for a change in DNA here and there. Just rare enough to not really change much, but to allow for change to be possible. These changes too are put out in each new generation.
Typically if the species is excellently adapted to its environment, and the environment doesn't change all, these genetic changes in each new generation aren't likely to provide an improvement so you don't see much change. This is known as stabilizing pressure.
But as soon as a new selective pressure appears, it will become clear that that species never actually retired from the evolution game.
ArbutusPhD t1_j9akdec wrote
Essentially, the rate of mutation in individuals may remain constant, but without some environnemental pressure exerting a selective effect on individuals with advantageous mutations, there is no reason for those mutations to become reinforced each generation.
If 1/1,000 people randomly have slightly longer fingers, but there is no pressure in the environnement that grants long-fingered people an advantage reproducing, you won’t see an increase in long-fingered people over time; there will remain a roughly 1/1,000 chance that anyone you meet is long-fingered.
[deleted] t1_j9c4a9w wrote
[removed]
mrshulgin t1_j9c52ui wrote
Given your explanation, would it be fair to say that species like that are "evolving in place?"
That is, they're still actively mutating, but the mutations are "undone" in successive generations.
I know I've simplified things a lot, but is this still a serviceable explanation of the concept?
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