The tyranny of design
How could sophisticated mechanisms such as the flagellar motor or the adaptive immune system have evolved without some guiding hand? Henry Gee finds his answer to the argument of Intelligent Design in the lamprey.
We are accustomed to thinking of ourselves as peaks of perfection, and the arrangements of more "primitive" creatures as similar to our own, only cruder. It's a nice idea. Until along comes the sea lamprey to challenge our preconceptions.
Researchers have found that the lamprey (Petromyzon marinus) has a has a sophisticated system of adaptive immunity, that is entirely different to our own. Many organisms have a kind of natural immunity, but the adaptive immunity of mammals was supposed to be something special. By dint of a kind of controlled chaos, specialized parts of our genomes rearrange themselves to produce antibodies, custom-built proteins that are then selected to target any kind of foreign molecule the world can throw at us.
One of the great mysteries of immunology is how and when this remarkable system originated. For many years, immunologists looked for its beginnings in lampreys, sucker-mouthed creatures that represent the earliest flourish of vertebrate evolution more than 500 million years ago. Lacking jaws and paired fins, lampreys are almost as primitive as a vertebrate can get. They seem to have adaptive immunity, but scientists haven’t found even a glimmer of any antibodies.
The fact that the work seems so surprising exposes another, more dangerous conceit that scientists are prone to. Dangerous, because it leaves science wide open to the temptations of so-called ‘Intelligent Design’. Advocates of this view object to evolution by invoking what Richard Dawkins has called the ‘Argument from Incredulity’ – that is, if I don’t believe that something is possible, it cannot happen. Philosopher William Paley in his Natural Theology famously used this argument when he compared the delicate designs of nature with a pocket watch. Pocket watches are not made spontaneously, so if the existence of a functioning, integrated watch implies a watchmaker, then the same must surely apply to a living creature.
More than a century later, proponents of Intelligent Design use the same reasoning when they marvel at the intricate design of, say, a bacterial flagellar motor. How can one ever give credence to the view that the sophisticated mechanism of the flagellar motor could have evolved to such precision without a guiding hand, when the tiniest of changes to its apparently irreducible complexity might render it useless?
I was discussing the problem with two polymathic friends of mine, reproductive biologist Jack Cohen and mathematician Ian Stewart, co-authors of Figments of Reality, Evolving the Alien and The Science of Discworld. They are working on their next book, Appearance of Design (to be published by Penguin next year) and Cohen sent me a draft chapter containing a devastating response to the challenge of Intelligent Design. It arrived on my desk at about the time that the work on the lamprey immune system was making waves in the Nature office, so it struck a particular chord with me.
But before we as scientists allow ourselves to be too smug, we should consider how our own attitudes are over-welcoming of Intelligent Design. Generations of biologists and medics have gone through school and college being exposed to a parade of ‘types’. We learned to dissect The Dogfish, The Frog, The Rat, as if each one was the only possible example of its kind. Diversity falls as an easy casualty of efficient learning, and grand generalizations of evolution are extrapolated from The Fly, The Worm, The Mouse and The Zebra-Fish.
Granted, this does make things simpler. But the unthinking adoption of this idea by many scientists gives the Intelligent-Design school an easy target and is the reason why concepts such as The Bacterial Flagellar Motor are not immediately laughed off stage.
The only way to gain a realistic understanding of how life works is to give students hands-on experience of the diversity that exists. I was lucky – at school I trawled the countryside for natural history specimens, rocks and fossils, while at college I had hands-on experience of the outsides (and insides) of all kinds of exotica. But the triple tyranny of risk assessment, cost and politically-correct squeamishness has now seen off such activities for all but a few.
I believe that unless biologists have dissected real animals or experienced natural diversity for themselves, they are not worthy of the name. It was this same exposure that sowed the seeds of evolution in the mind of the young Darwin, turning him away from the theoretical, typological views of German Naturphilosophie that resonate still in those who argue for the presence of a designing hand. The artificial environment of the lab rat is as rarefied as the thoughts of Plato and Aristotle, the philosophy from which this idea derives. It no coincidence that it is in these very environments that Intelligent Design finds its most willing converts.
- Pancer Z. et al. Nature, 430, 174 - 180, (2004).