RE: The code that is DNA
December 29, 2019 at 7:10 am
(This post was last modified: December 29, 2019 at 7:31 am by John 6IX Breezy.)
(December 29, 2019 at 2:26 am)LadyForCamus Wrote: I don’t see what is so hard to understand about the idea that enough small changes from generation to generation will eventually render the “first” and the “last” generation in the series reproductively incompatible. That the changes are small and slow doesn’t render them insignificant, because they’re cumulative.
I understand the idea; it's just not a good one. It's better to disassociate many of these variables from one another. For example, if polyploidy occurs in a plant, doubling the set of chromosomes, then within a single generation you might have reproductive isolation. Then there are extant species like the horseshoe crab, which have accumulated much genetic variation over vast periods of time, but are otherwise morphologically and reproductively the same.
So we see that slow and small cumulative changes alone doesn't make the first and last generation of horseshoe crab sexually incompatible (not that it's possible to test). But a sudden and large non-accumulated change, like polyploidy in plants, can. Those two narratives contradict what you just said.