Evolution of vascular systems


Once upon a time, in Paris in 1830, Etienne Geoffroy St. Hilaire debated Georges Léopole Chrétien Frédéric Dagobert, Baron Cuvier on the subject of the unity of organismal form. Geoffroy favored the idea of a deep homology, that all animals shared a common archetype: invertebrates with their ventral nerve cord and dorsal hearts were inverted vertebrates, which have a dorsal nerve cord and ventral hearts, and that both were built around or within an idealized vertebra. While a thought-provoking idea, Geoffroy lacked the substantial evidence to make a persuasive case—he had to rely on fairly superficial similarities to argue for something that, to those familiar with the details, appeared contrary to reason and was therefore unconvincing. Evolutionary biology has changed that — the identification of relationships and the theory of common descent has made it unreasonable to argue against origins in a common ancestor — but that difficult problem of homology remains. How does one argue that particular structures in organisms divided by 600 million years of change are, in some way, based on the same ancient organ?

One way is sheer brute force. Characterize every single element of the structures, right down to the molecules of which they are made, and make a quantitative argument that the weight of the evidence makes the conclusion that they are not related highly improbable. I'll summarize here a recent paper that strongly supports the idea of homology of the vertebrate and arthropod heart and vascular systems.

Continue reading "Evolution of vascular systems" (on Pharyngula)


Rather sad to see that this post hasn’t got any comments, but I can’t really say much about it either because I never knew there was an Etienne Geoffroy St. Hilaire until I read it.

Proving the origins in a common ancestor and tracking its evolutionary branching is exactly the kind of detail that kills Intelligent Design. Yet, not many people have anything to say about it here.

Off topic: PZ, have you ever thought about writing a book similar to the kind that Dawkins and Harris have written? Something that you could give a title like “Religion is a Psychosis,” (fit in their with “God Delusion”). Consider:

1) The Dawkins and Harris books have sold well. (Money to make there) 2) You’ve accumulated enough material on your Pharyngula blog already. (All those posts on Chopra, creationist nuts, etc.) 3) Promotion for the book would add to your blog readers and visa versa. 4) You’ve got more scientific credibility than Harris, though not quite as much as Dawkins. 5) You’ve got an angle in your blog they don’t have.

If you want any help, email me at [Enable javascript to see this email address.]. I just recently gave Chris Mooney a hand on his new book, “Storm Planet.”

Sometimes I expect PZ’s science posts draw fewer comments over here* just because they tend to draw plenty of comments–and often from the same bunch as would otherwise weigh in here–over on Pharyngula

________ *And, of course, some of us over here are just so unswervingly loyal to Lenny’s memory that we couldn’t be bothered to comment no matter how excellent PZ’s science commentary was. And no matter how many blog awards he racks up. And no matter how righteously he rousts those IDers. And no matter how…

Alas, poor Geoffroy.

Science posts get relatively little comment anywhere, here or at Pharyngula, because they generally aren’t controversial, the IDiots notwithstanding.

I am working on a book. I’m looking forward to the coming holiday break when I hope to make some substantial progress on it. My working title so far is “Natural Revelation”. The theme isn’t so much “gee, you religious people are psychotic” as “gee, you religious people are missing out on the most exciting stuff.”

Oh, and Lenny was an addlepated twit with nothing to say.

Anybody around here some fellow called Mark “Stud-Duck” been seeing?

My goodness, they are so squirrely being, these little trolls!

PZ sure does love to start them flamewars.

(Pours a considerable quantity of an oddly-colored liquid out of a brown bottle bearing a cheaply-photocopied label showing a hugely-grinning guy sporting hairy “Rat Fink” eyeballs and also wearing a dented helmet sprouting cow’s horns: Hissss!)

So much foah flame-wahs, dahlin’!

PZ wrote:

My working title so far is “Natural Revelation”.

Mmmm… sounds like it’ll sell as numerously as the comments on your science posts.

I suspect marketing will want a more in your face title – and your posts on Ken Ham and Dembski have been really in your face stuff.

Have you talked to a publisher? (I’d bet “The God Delusion” wasn’t Dawkins first choice for a title.)

The theme isn’t so much “gee, you religious people are psychotic” as “gee, you religious people are missing out on the most exciting stuff.”

Why not a bit of both?

Anybody around here some fellow called Mark “Stud-Duck” been seeing?

“Mark Studdock” is a character from C.S. Lewis’s Christian polemic “That Hideous Strength”. He’s an atheist and a social climber who is always seeking to be in the “inner circle”; this leads him into an evil organization, “NICE” (National Institute of Coordinated Experiments). The troll, by calling himself “Mark Studduck FCD” is equating NICE with FCD (Friends of Charles Darwin). These are the sorts of games these corrupt Creationists play.

Oh, and Lenny was an addlepated twit with nothing to say.


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This page contains a single entry by PZ Myers published on December 19, 2006 6:00 PM.

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