Summary: He says that on the molecular level th speed is probably relatively constant and much faster than anyone would naively expect. However, since the mapping from DNA bases to amino acids, the mapping from amino acids to protein geometry, and the mapping from protein geometry to phenotypic properties are all many-to-one mappings, the massive but relatively constant mutation rate on the molecular level can lead to a very wide range of mutation rate in the phenotypic level, from the relatively negligible to the astoundingly fast.
I should have read that before starting to watch it. I loved his kitschy shirt, though
Honestly, though, that doesn't really clarify the issue for me, just Dawkins's view. I'm still not sure he's presenting PE as it was presented, and I'm not sure Eldridge/Gould lacked an understanding for the chemical processes behind evolution when they proposed their theory--Did they?
I take issue with the idea of an evolutionary "speed". Mutations occur at a generally constant rate, regardless of the phenotypic effect. What happens in punctuated equilibrium is that a very rare mutation (or series of sequential mutations -- see the recent paper on citrate metabolism in E. coli) gives a large selective advantage to an individual. Evolution appears to "speed up" because selection is so strong towards the new phenotype, but the underlying mutations are still occurring at the same speed.
Yeah, exactly, and I didn't think that's what PE described. Variation doesn't stop, I was under the impression that PE suggested that under certain conditions a population can dramatically "change" rather quickly, or rather their environment can select for a trait (perhaps from a mutation as dramatic as frame shift) bringing about changes very quickly, say bony fins and maybe elbows
I thought PE was just a theory to explain "explosions" in speciation following some event wiping out the dominant life forms.
Me too, man!
yeah but mutations dont' always lead to a change in a species (if it's not a beneficial mutation, the mutated individual has a lower chance of suvviving and passing on the mutation) - and evolution usually means a change in a species.. right?
so when you say "speed of eovlution" you're usually referring to how fast a species is changing over time, no matter the fact that mutations happen at the same rate (ie. one per generation)
Yeah, that's a much better way of putting it than what I wrote above.
Evolutionary biologists don't usually think of evolution in terms of speciation. The term "species" is so loosely defined that it's hardly useful in anything but colloquial use.
Then I'll use more precise language: A certain, identifiably unique, new trait (we're talking on an organism level, I don't think I could accept the suggestion that the traits of the whole organism are irrelevant just because of a constant rate of mutation at the cellular level) that provides an advantage to the survival of the changed species.
Dawkins put it well in the video Nihilistic posted, just got to this part. Speaking of punctuated equilibrium: "[...] Even very slight selection pressures could give rise to evolutionary change so rapid that it would be indistinguishable from instantaneous on the fossil record." Dawkins went on to say "[...] Sometimes evolution goes so rapidly that it doesn't show on the fossil record,
particularly when it happens in another place, as it so often does." Does this sound accurate? Is PE more about accounting for what seems like sudden change or gaps in the fossil record?
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I prefer Neil Degrasse Tyson, if I had to pick a prominent scientist. At least he's cuddly and has a nice mustache 