Galapagos Diary: Neo-Darwinism Lecture, Part 1
Richard gave his first of two lectures on Neo-Darwinism after our visit to the young island of Fernandina (account of this coming up) on Sunday (Mother's Day). This is where he first introduces the neutral theory (at 41:11) , and I ask a question about that (at 53:50) during the Q&A.
Here are some of my notes on the lecture, which also includes a brief history, that I will not reproduce here, of the evolution (sorry) of Darwin’s ideas through Mendel’s observations, the Neo-Darwinian Synthesis, and Punctuated Equilibrium, up to the present day:
The title of Darwin’s sixth edition of On the Origin of Species by Means of Natural Selection should have included and All Sorts of Other Things. The first edition is closer than the sixth and last edition to our modern view of Darwinism. Darwin was pressured into adding the words “breathed by the Creator into,” but the first edition the phrase was just “breathed into.”
Darwin explained both diversity and adaptation. Natural selection is the only theory that can, in principle, explain adaptation. The only “rivals” are design and Lamarckanism.
The neutral theory doesn’t explain adaptation. The premise is that many mutations are neutral – not useless, but equivalent to the original codon. Any amino acid can be coded for by more than one codon, resulting in synonymous mutation.
Synonymous mutation equals zero mutation.
The majority of evolution is neutral. However, phenotypic change is not neutral to a field naturalist (ethologist).
The coding of an amino acid effects a phenotypic change only insomuch as it affects the shape of the protein, which has an enzymatic effect.
Here are some of my notes on the lecture, which also includes a brief history, that I will not reproduce here, of the evolution (sorry) of Darwin’s ideas through Mendel’s observations, the Neo-Darwinian Synthesis, and Punctuated Equilibrium, up to the present day:
The title of Darwin’s sixth edition of On the Origin of Species by Means of Natural Selection should have included and All Sorts of Other Things. The first edition is closer than the sixth and last edition to our modern view of Darwinism. Darwin was pressured into adding the words “breathed by the Creator into,” but the first edition the phrase was just “breathed into.”
Darwin explained both diversity and adaptation. Natural selection is the only theory that can, in principle, explain adaptation. The only “rivals” are design and Lamarckanism.
The neutral theory doesn’t explain adaptation. The premise is that many mutations are neutral – not useless, but equivalent to the original codon. Any amino acid can be coded for by more than one codon, resulting in synonymous mutation.
Synonymous mutation equals zero mutation.
The majority of evolution is neutral. However, phenotypic change is not neutral to a field naturalist (ethologist).
The coding of an amino acid effects a phenotypic change only insomuch as it affects the shape of the protein, which has an enzymatic effect.
Labels: Dawkins, evolution, Galapagos Diary
posted by Kristine | Thursday, June 28, 2007
7 Comments:
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You got to ask him a question and he addressed you by name! Ooooh!
Interesting follow-up to your question:
Richard said that a mutation that changes an amino (ah-my-no) acid might still create a functionally equivalent protein (because it folds the same way) that is invisible to natural selection. This is quite true; there are different versions of the "same" protein existing in many populations in nature.
What's interesting is that opposite can also be true. For example, it's plausible (I say plausible because the study of microRNA's is so new that I think that there isn't any experimental evidence yet to back up my claim) that a mutation to a codon could code for the exact same amino acid, therefore generating the same exact protein, yet its mRNA and tRNA would behave differently towards the regulatory microRNA and hence cause a phenotypic change. Just something to think about.
Well, that's a new one on me (as was the neutral theory itself).
So I wonder what precisely determines a change or not in the phenotype? I have been thinking about it. It's a real puzzler.
This illustrates how infantile the creationist's claim is that "nobody has seen" macroevolution, etc., when here, as with many if not all things, change is not visible. The effects of change are, and we can say that they have occurred. And this goes for personal change, too - we become the person that we are by a series of small steps - there's no one point where we suddenly "change" (although that's the idea behind religious conversion, which sets people up for disappointment, I think).
Richard is a very good lecturer, a good teacher. He probably gets the same questions time and again and he's patient; he obviously wants people to get this stuff; he doesn't withhold anything or try to manuever people.
So I wonder what precisely determines a change or not in the phenotype?
I'm guessing that from a molecular biologist's point of view, there are so many competing reactions going on that predicting the phenotypic effects would be futile (as of today). Although as a big fan of chaos theory, I'd like to think that while individual phenotypic effects might be unpredictable, a general (and symetric) pattern should emerge from out of the chaos.
The creationist idea that there is an inherent difference between species (as we know them today) and that therefore a change must require a speciation event is inherently ridiculous. In fact, despite creationist's protests to the contrary, Gould's punctuated equilibrium is perfectly compatible with what Richard was saying. ie. a field biologist taking careful measurements would be unable (in his lifetime) to know whether he were living in an era of equilibrium or one of punctuation.
Richard is a great lecturer (as well as author), but I bet he hasn't had the microRNA question yet. (I confess that coming up with novel questions is kind of a point of pride for me.)
~Javier
ps---Did anyone ask him an evo-devo question?
You know, when I e-mailed him almost a year ago I asked him your question, but that was just before he launched the website and foundation, and I think it got lost in the shuffle. I thought of it on the ship, but from talking with and watching him I get the sense that his passion is animal behavior. Plus, he kept talking about ideas for his next book and I didn't want to change the subject! ;-)
I'm going to the AAI conference this fall (yep, all I need to do right now is spend more money!) so maybe I'll ask him then, if I can get near him with hundreds of people there. I hope he remembers me then. :-) I don't know how he can keep so many people straight. I got a glimpse of what it is like to be very well known, although too, people on the ship were respectful and polite. But there were times when I thought, "Geez, if that were me I'd probably snap someone's head off at this point, or just go hide!" and of course he never did.
cool blog...loved the dawkins lectures, as well as his books!
keep it up!
Thank you for visiting, BluntDissector. There's more to come!
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