Thursday, February 14, 2008

Evolution’s Engine

The ongoing wars over the teaching of evolution (particularly in the US) have elevated into public consciousness an unlikely topic: molecular microbiology. Modern day creationists, rebranding themselves as ‘Intelligent Design theorists’, have made sweeping, not to say unfounded, claims about the limits on the power of evolution on the basis of a tiny nanomachine called the bacterial flagellum.

This complex structure, made of about 40 interacting proteins, is essentially an outboard motor that powers bacteria through their watery environment. At the heart of the flagellum is a rotary motor that drives a long, whip-like tail, which propels the bacterium as it spins round. It is a magnificent work of molecular engineering (see below).

For ID theorists, it is more than just awe-inspiring in its complexity and elegance. To them, it speaks of intelligent design. For tactical reasons the nature of this designer is often left unspecified. Yet the context of these claims makes it clear that a notion of a creator, of the kind found in Judaeo-Christian cosmologies, is lurking behind the scenes.

In essence, ID is a resurrection of an idea with an old pedigree: the ‘argument from design’ that the apparent plan and purpose in nature call for divine explanation. The most famous incarnation of this argument was bequeathed to us by English philosopher William Paley in 1802. Paley suggested the following thought experiment. Imagine that, walking across a heath, you stumble upon a pocket watch, and ask yourself “How did this object come into existence?”. A mechanical watch is a complex, highly engineered device, whose interacting parts contribute to the overall purpose of accurately telling the time. It is clearly massively unlikely that the components of the watch achieved their specific forms through natural processes, and then just happened to come together by chance – and then work to serve a useful purpose. No, the existence of watches requires the existence of skilled watchmakers. And by analogy, the wonders of nature reflect the efforts of a thoughtful, intelligent, purposeful creator*.

Of course, for evolutionary biologists there is no cosmic engineer or molecular draftsman drawing up plans as part of some biological hobby. The cumulative power of descent with modification — Darwin’s theory of natural selection, in other words — is the ‘blind watchmaker’ of evolution. No cosmic designer needed, thank you. As such, evolutionary-minded microbiologists, geneticists and molecular biologists have felt the need to step up to the charge that the bacterial flagellum is ‘irreducibly complex’, unevolveable, and in need of an intelligent designer to explain how it can exist.

The topic — explaining functional biological complexity at the molecular level — is, of course, of much broader interest. From a purely academic angle, irrespective of the political campaigning of IDists (or IDiots, as some say), the bacterial flagellum is exactly the sort of system we should be looking at the test and refine ideas about the various mechanisms, and specific routes, by which biological complexity arises.

And this is just what scientists have been doing in recent years. In this week’s New Scientist, I have a feature on what has been found, and what remains unclear, in flagellar research. Scientists do not claim to have wrapped up the story on flagellum evolution. But what is more interesting is the way recent scientific debates about the flagellum highlight the intellectual bankruptcy of ID theory. If you took the ID case seriously, you’d say “OK, the flagellum is irreducibly complex and could not have evolved – done.” You might then move onto the next difficult issue in evolutionary biology, and say the same.

The scientists I spoke with, by contrast, have a rather different epistemological approach. Yes, the evolution of complex molecular machines poses difficult questions, but that’s what makes them interesting and rewarding to study. And it’s not that evolutionists just want to club together to shout, “Look, the flagellum evolved – job done!”. They want to get some real explanatory purchase on the problem.

This concern with actually working out the details inevitably throws up different ideas, which other scientists then critically evaluate. Analyses are criticised, hypotheses scrutinised and conclusions questioned. This is the sign of healthy science in action; it leads to real insights and refined understanding. In short, the evolutionary approach is a genuinely testable theory, and a viable research programme. Falling back on ID, on the other hand, reveals an intellectual lack of nerve. Where evolutionary biologists face up to the mysteries the universe presents, and are prepared to put in the hard work required to crack them, IDists give up on trying to reach any sort of understanding whatsoever.

*’But who created the creator?’, you should rightly ask. We may reasonably suppose that a creator of biological splendour would be as complex and apparently ‘planned and purposeful’ as the biological ‘creations’ we want to explain. If so, the existence of this creator also needs explaining. To side step this in issue reflects an outrageous double standard: that complexity and apparent purposefulness and design in one domain (nature) require explanation – so much so that might even feel compelled to infer a cosmic creator from them — but that in another (creator gods) such features are a given. It’s no better than when someone points out one of our own double standards, and we weakly try to justify the inconsistency between the standards we apply to others and those deployed in our own conduct by saying “But you see, in my case it was different….”

For more on the flagellum, see:
http://www.millerandlevine.com/km/evol/design2/article.html
http://www.pandasthumb.org/archives/2007/04/flagellum_evolu_1.html

8 Comments:

Anonymous Mike from Ottawa said...

Good article, thanks, Dan.

However, a nit: that's no outboard motor. It's an inboard motor. Only the 'propeller' and part of the 'propeller shaft' is outside the cell wall. The parts that produce the rotary motion are inside the cell.

4:45 pm GMT  
Blogger Dan Jones said...

Fair point Mike - though if we're being really picky, we might say that the flagellum is neither an inboard motor nor an outboard motor, as the rotary engine part is not strictly inside or outside the cell, but embedded in the membrane of the cell (by analogy, this would be like a motor that was neither outside a boat’s hull, not inside it, but built into the hull wall). In any case, glad you like the article!

D.

2:59 pm GMT  
Blogger Spidergrackle said...

"And it’s not that evolutionists just want to club together to shout, "

Please don't use the word "evolutionists" to describe members of the the scientific community. It's bad enough that we have the creationists trying to rewrite the language to make acceptance of ET look dogmatic: we don't need folks on our side of the aisle helping them in blurring the line between blind faith and scientific certainty.

/rant

Chuck C

9:11 pm GMT  
Blogger Dan Jones said...

Why does 'evolutionist' imply blind faith any more than ‘biologist’ or ‘physicist’ does? I used the term to denote those that study evolution and accept it as a natural process that has played out over the last 4 billion years on Earth – not on blind faith, but on theory and evidence. As for scientific certainty, many biologists are as certain that evolution occurred, and that natural selection is key mechanism effecting evolutionary change, as they are of any other scientific theory. Again, this is not dogmatism or blind faith, but an attitude supported by more than 150 years of theory development and evidence gathering.

12:22 pm GMT  
Blogger dobson said...

Why does 'evolutionist' imply blind faith any more than ‘biologist’ or ‘physicist’ does?

"Biologist" and "Physicist" are words that denote scientific professions. So is "Evolutionary Biologist", on the other hand the word "Evolutionist" merely means somebody who accepts the theory of evolution. It's a category mistake to lump this word with the other two.

I used the term to denote those that study evolution and accept it as a natural process that has played out over the last 4 billion years on Earth – not on blind faith, but on theory and evidence.

The problem with adopting the creationist term "Evolutionist" when referring to the overwhelming majority of biologists who accept the Theory of Evolution is that we have adopted what is essentially a creationist framing device.

The creationists would like to frame the argument as an even-sided dispute between the "Evolutionists" and the ID proponents.

By using their word you are implicitly accepting this false-balance.

6:13 pm GMT  
Blogger Dan Jones said...

OK, there seems to be a bit of confusion about the word ‘evolutionist’. Dobson agrees with me that the word simply means someone who “believes in or advocates the theory of evolution; and expert in or student of evolution” (OED). In which case it implies no more blind faith than speaking of an entomologist etc – that was all I was saying, not that being an evolutionist is a profession like being a biologist. Saying that the term ‘evolutionist’ implies no more faith than ‘biologist’ is not to make a category mistake in any case (that would be more like being shown around the various Oxford Colleges – All Souls, Baliol, Brasenose etc – and then asking, “Yeah, but where’s Oxford University?”).

To be honest, I didn’t think that the term would be perceived as a concession to creationist terminology. And I don’t think I’m alone in that. Giants of evolutionary theory such as G. G. Simpson and Ernst Mayr described themselves as evolutionists; more recently, Richard Morris had a short book out about current debates in evolution (not specifically creationism, and written from a scientific perspective) called ‘The Evolutionists’; and Darwin@LSE – which used to be an important intellectual salon for airing Darwinian ideas in the UK – had a series of online interviews (with people such as E.O. Wilson, Richard Dawkins, John Maynard Smith and George William) conducted by ‘The Evolutionist’ (http://www.lse.ac.uk/collections/darwin/evolutionist/index.htm).

So contra Spidergrackle and Dobson, I think being afraid to self-apply the term evolutionist – which, as we’ve said, is merely to acknowledge that you accept the theory of evolution - is to concede at least one semantic battle with creationists. Why let them make ‘evolutionist’ a dirty word? But really, I’m not particularly fussed about using the word, so if it makes peoples’ ears prick up, then it is perhaps best avoided. Thanks for tipping me off to this possibility.

7:01 pm GMT  
Blogger dobson said...

So contra Spidergrackle and Dobson, I think being afraid to self-apply the term evolutionist – which, as we’ve said, is merely to acknowledge that you accept the theory of evolution - is to concede at least one semantic battle with creationists. Why let them make ‘evolutionist’ a dirty word? But really, I’m not particularly fussed about using the word, so if it makes peoples’ ears prick up, then it is perhaps best avoided. Thanks for tipping me off to this possibility.

Were it not for the ID types who are trying to re-define our language we would all be proud to self-apply the word "evolutionist". It is as you say a good summary of beliefs.

On the other hand, we need to recognize that Intelligent Design is not science but a form of culture-war being waged against what it's soldiers see as "materialist culture" and "secularism".

This is why a purely scientific critique of ID ideas will never be sufficient - you have to engage at a political level because that is what they are doing.

The big problem I have is to strike a balance between recognizing the problem and not adding fuel to the fire. Your article on Flagellum evolution is interesting in it's own right (regardless of the interpretations for ID), however we can be sure that somewhere in the "ID Movement" somebody will claim that if the New Scientist is starting to "Debate" ID then there must at least be some merit to their claims.

Sooner or later your own words will be taken out of context to prove a point entirely opposed to what you believe. See how these things work? It's not about the science - it's spin, distortion and politics.

:-)

9:10 am GMT  
Anonymous Anonymous said...

Thank you for the interesting article and I also enjoyed the comments. I study biological anthropology and it is so frustrating to see the term 'evolution' and 'biology' has become so dirty and bad words in social sciences in general and (cultural)anthropology in specific. What they teach in the beginning of the cultural anthropology class is that the wrong idea of cultural evolutionism, and Spencerism which has nothing to do with the original theory of natural selection. It is almost a mental torture to see them teaching students that humans go beyond our 'biological' limits with the power of culture. So I think that the "battle" between the scientific minds and those of religion (or agnosticism)will never end no matter how long human history continues.

9:51 pm GMT  

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