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: