A few days ago I posted pictures of the telegram notifying Francis Crick that he had won the Nobel Prize [Wellcome Trust Images]. The photos were from the Wellcome Images website.Since then, a number of bloggers have commented on a brief note that Crick wrote on the back of a letter in 1989. I deliberately skipped that image last week because I thought it was embarrassing. I still do, in spite of the fact that the famous PZ Myers has declared it a nice quote [That's a nice quote].
What's so nice about it? It looks pretty stupid to me. What is there about DNA that gives support to evolution by natural selection—or even just "evolution" for that matter? Are my fellow bloggers just mesmorized by the juxtaposition of Francis Crick's name with the words "evolution" and "natural selection"?
Remember that 1989 corresponds to Crick's dotty period in La Jolla.
[Some people will argue that the sequences of various DNA's from different species lend support to evolution. Of course that's true but it's not what Crick wrote and I doubt very much it's what he meant. He was probably thinking about the beauty of the DNA molecule and it's appearance of "design" by natural selection.]
Ahh, yes. Glad someone else views Crick's interests at the Salk in a similar fashion. I always think this is one of the primary examples of people thinking they are brilliant at everything, just because they are acclaimed for some other bit of brilliance. The "Astonishing" hypothesis was anything but...
ReplyDeleteSome people will argue that the sequences of various DNA's from different species lend support to evolution. Of course that's true but it's not what Crick wrote and I doubt very much it's what he meant. He was probably thinking about the beauty of the DNA molecule and it's appearance of "design" by natural selection
ReplyDeleteNo, I think Crick very much meant DNA sequences. Crick was the father of molecular phylogeny (even before Zuckerkandl and Pauling). Read this incredible, prophetic quote of his from 1958.
"Biologists should realize that before long we shall have a subject which might be called 'protein taxonomy' -- the study of amino acid sequences of proteins of an organism and the comparison of them between species. It can be argued that these sequences are the most delicate expression possible of the phenotype of an organism and that vast amounts of evolutionary information may be hidden away within them."
-- Francis Crick "The biological replication of macromolecules" (1958).
(Yes, you may argue he was talking about proteins and not DNA in this quote -- but that's because Sanger had shown how to sequence proteins in 1955 and it wasn't until much later that DNA sequencing methods developed.)
Discovery of the structure of DNA made it clear how the mechanism of heredity worked -- and similarly, the mechanism of mutational change. This finally connected old-fashioned population genetics (the previous incarnation of mutation+selection) up with the molecular mechanisms and showed that, yes, it could all work.
ReplyDeleteI don't think there is more to it than that...what's your beef, exactly?
I wonder if Crick was thinking that DNA boosts evolutionary theory because it's possible to see how the specific DNA language that our genes use could have evolved. It's easy to make up DNA-codes that don't have this quality, but we don't use any of those codes. To a biochemist it could look like the ultimate test of evolution's plausibility: if every other piece of evidence said "evolution yes" but the genetic code itself said "evolution no," it would still be a theory-killer.
ReplyDeleteBadger: you say Crick was the father of molecular phylogeny. Then what was George Henry Falkiner Nuttall? Chopped liver?
ReplyDeleteWell, not to deny Nutall's contributions to science, but considering serum based studies like Nutall's to be "molecular" is really stretching the definition of "molecular" beyond what is generally understood by the term. Unless you mean something other than his serum work that I don't know about.
ReplyDeleteMostly I'm amazed by Crick's quote because textbooks and review papers generally present Zuckerkandl and Pauling's "Molecules as Documents of Evolutionary History" (1965) as being the origin of the idea of molecular sequence phylogeny.
And it shows Crick wasn't just some chuckle-headed structure wonk who was into the "beauty of the DNA molecule" as Larry suggested he was, but rather someone who really thought deeply about the implications of molecular biology for phylogeny.
Of course we shouldn't be using Larry's page for a discussion, and I totally agree with your assesment of Crick. I guess we'll have to disagree on whether serum-based studies are "molecular". I believe they are, because at base the antibodies are responding to molecular structure. You may not, because Nuttall didn't conceive of them in that way, as far as I know.
ReplyDeleteEither way, I think we can both agree that Zuckerkandl did not originate the idea.
Jonathan Badger,
ReplyDeleteAnd it shows Crick wasn't just some chuckle-headed structure wonk who was into the "beauty of the DNA molecule" as Larry suggested he was, but rather someone who really thought deeply about the implications of molecular biology for phylogeny.
Francis Crick is one of my heros. I got to meet him on several occasions when he was in his prime and I was awed to be in his presence. He was one smart cookie when it came to theorizing about how life worked at the molecular level.
However, his understanding of evolution left a great deal to be desired. He was a firm, and naive, adaptationist who was much more comfortable with the ideas of Richard Dawkins than Jacques Monod.
Crick started his biological career in in a lab where Sanger and his group were sequencing insulin back in the 1940's. He kept in touch with them throughout the 1950's. The idea that proteins from different species would reflect evolution was very common back then. Everybody knew that some genetic diseases were due to alteration in the sequence of amino acids.
Zuckerkandl and Pauling did not come up with the idea but they were the first to publish a widely read paper where multiple sequences were combined to produce a phylogenetic tree.
I still think that Crick was not thinking of DNA sequences when he said that "the most significant aspect of DNA is the support it gives to evolution by natural selection." If he was, then he's dead wrong because those sequences do NOT support natural selection. They may provide support for "evolution" but most of that evolution is by random genetic drift.
Since the comment was made in 1989, I think what Francis Crick was referring to was the idea of the Central Dogma, which emerged almost directly from understanding the structure of DNA. This idea is that information in the biological system can go from DNA to RNA and RNA to protein, but not from proteins to RNA or DNA. (note, information, not action) This idea, which was very clearly articulated by a Crick in his review "On Protein Synthesis", explained why evolution must happen by natural selection and not by lamarckian means. He referred to this explicitly in the review.
ReplyDeleteAlso, I would object to points referring to his time at Salk as fruitless. I would strongly urge you to read his papers on Consciousness. One clearly sees that while they did not come with even a partial theory, they did not claim to either. The approach he and Koch suggested is clearly the most logical and sensible one, and has led to productive research into the field. Crick made several predictions while at Salk, which have turned out to be correct. One was the molecular mechanism of memory that he proposed. The second was the theory that spines twitch. Both of these have been empirically verified.