Evolving Thoughts

Evolution, culture, philosophy and chocolate! John Wilkins' continuing struggle to come to terms with impermanence... "Humanus sum, nihil humanum a me alienum puto" - Terence

Thursday, November 17, 2005

Not my fault...

Sahotra Sarkar is assigning me the blame for the extension into the Australian body politick of Intelligent Design. All I can do is offer the Bart Simpson defence: I didn't do it, I wasn't there, and nobody saw me do it. Unless there's money in it, in which case email me for the address to send the cheque (no electronic transfers, thanks - I'm still waiting for that $20 million to arrive from South Africa, or was it Nigeria?).

I already assigned blame...

The Mosasaur and the missing link

A new fossil mosasaur, one of a group of non-dinosaurian reptiles that return to marine existence, has been found by an amateur fossil hunter (see? Science can be done by non-professionals) near Dallas Texas, appropriately called Dallasaurus turneri after the location and discoverer Van Turner who found it 16 years ago.

This fossil is interesting because it is one of your classical "missing links". Mosasaurs, which ended up 40 feet long (12m) at the end of the Cretaceous when they and dinosaurs and a whole lot of other life went extinct from a bolide impact, evolved fins from their limbs, and many of the primitive mosasaurs had partial limbs/fins.

D turneri, however, has the complete set of limbs it shared with its reptilian ancestors and cousins. This is interesting for mosasaur specialists of course, but it also allows me an opportunity to talk about two often-misunderstood terms in evolution - "missing link" and "primitive".

Our mosasaur is "primitive" because he (she?) shares the ancestral state rather than the later derived state. "Highly evolved" mosasaurs like the Mosasaurus monster that lived at the Cretaceous end, were not "more complex" or "more advanced" except in the sense that they had changed from the ancestral condition. Had the later mosasaurs re-evolved feet from their fins (and we can be pretty sure they would not be a simple reversion, since so many developmental paths and genes would have been deactivated) then that state would have been "more evolved" or "advanced", and the fin condition "intermediate" and the original feet "primitive". The very word "primitive" means "came first". That's all it means. Only because of a progressionist view of history due to the pre-Darwinians does it mean "less complex" or "less developed" in our ordinary use, and Darwinian evolution does not imply that it had to be simpler.

That brings us nicely to "missing link". In the view of history and being known as the scala naturae, or "ladder of nature", things grade slowly from simple to complex, in a worldview dubbed The Great Chain of Being, after an Alexander Pope poem, Essay on Man (Epistle 1, 1732):
See thro' this air, this ocean, and this earth
All matter quick, and bursting into birth:
Above, how high progressive life may go!
Around, how wide! how deep extend below!
Vast chain of being! which from God began;
Natures ethereal, human, angel, man,
Beast, bird, fish, insect, who no eye can see,
No glass can reach; from infinite to thee;
From thee to nothing.--On superior powers
Were we to press, inferior might on ours;
Or in the full creation leave a void,
Where, one step broken, the great scale's destroyed:
From Nature's chain whatever link you like,
Tenth, or ten thousandth, breaks the chain alike.
If the chain is a continuous gradation as Pope and those who influenced him, all the way back to Aristotle but particularly in the renaissance and after, believed, then a gap means a "missing link". And clearly, if the Great Chain is a temporal sequence, then the earlier is simpler, and the later more complex. So it followed, and this was the way it was understood by Lamarck, the first widely-read evolutionist, that if humans evolved from earlier forms, they were simpler, and there should be no gap in the sequence. Hence, to show that we did evolve over time, there needed to be evidence of our immediately prior, simpler ancestors. If they were missing, they were a missing link.

But that wasn't Darwin's version of evolution. No simple ladder of nature, no chain. Evolution was, for him, a tree, and it didn't follow that any later branch was smarter, stronger, bigger, or more complex. In fact, he documented cases of vestigialism and regression himself, particularly in his barnacles book.

Darwin's tree diagram from The Origin of Species.

So a missing link might in fact be very similar to the earlier and the later forms, or it might be radically different from either one. Moreover, an intermediate form might be a mosaic of two groups rather than a smooth blend, as Archeopteryx and the recent Chinese feathered dinosaurs are between birds and (other) theropod dinosaurs. A smooth blend form is only to be expected on the Great Chain version of evolution. Moreover, if a period of geological history (shown in his diagram as "layers" of strata I...XIV) is not recorded for a branch or lineage of the tree, then there most certainly will be missing links. We expect them.

So I hope this helps explain some of the unintuitive aspects of evolution. Common sense is informed here by centuries of doctrines that we no longer think are true.

Tuesday, November 15, 2005

Past my use-by date

Well, I survived my 50th birthday, and celebrated it by moving house and welcoming my son to stay with me. The rest of the family move up over the next six weeks.

This means that I must lessen the amount of blogging for a while, and work on my ... umm... work. Go read Pharyngula for education and entertainment.

But a couple of points for now:
  1. Intelligent Design has been shown in court to be rebadged creationism, and its leading proponents have been, shall we say, dissembling over that point. We hope that the judge, who has shown a healthy sense of the ridiculous and humour, will rule sensibly. This will not stop the ID movement in any way. They are a political, not a theological or scientific, movement. They aim to control the minds of those who will constitute the next generation of legislators, in order to establish what can only be described as a religious society of intolerance. They haven't lost, but they are very far from winning, and we must remain vigilant to ensure that they don't. One thing that has struck me most of all about this is Steve Fuller's support from ID as "possible science". Fuller is a well-known "sociology of scientific knowledge" (SSK) academic in the UK (although he is originally from the US). His "expert witness" deposition boiled down to "we can't prove it's not science so let it in" which is, as I have said before, epistemic nihilism. It goes to reinforce my prejudices about SSK: they don't actually care about knowledge, but about power relations. It is epistemological democracy gone mad - as if being elite in knowledge production was a bad thing. On reflection, Fuller is a perfect ally for ID, because they both reject the notion that we can actually find out about the world.
  2. The other is that Gavrilets continues to inspire me. I wish that I had sufficient math to be able to follow every equation and work out the implications, but I don't. So my point here kids is: learn your algebra, trig and calculus. Not because it will help you do anything, but because it is the mark of a properly educated person. [Yes, this makes me uneducated, but I knew that already. I'm self-educated, and I blame my teacher. Seriously, I had very many good teachers late in my education, and very many poor teachers early. The reverse would have been much better.] Gavrilets will lead me to make more posts on speciation later.