Published online 3 May 2010 | Nature | doi:10.1038/news.2010.215

Column: Muse

Our genome won't win any design awards and doesn't speak well of the intelligence of its 'designer', as Philip Ball explains.

Helena: They do say that man was created by God.

Domin: So much the worse for them.

This exchange in Karel Capek's 1921 play R.U.R., which coined the word "robot", is abundantly vindicated by our burgeoning understanding of human biology. Harry Domin, director general of the robot-making company R.U.R., jeers that "God had no idea about modern technology", implying that the design of human-like bodies is now something we can do better ourselves.

Whether or not that is so, the human body is certainly no masterpiece of intelligent planning. The eye's retina, for instance, is wired back to front so that the wiring has to pass back through the screen of light receptors, imposing a blind spot.

Now John Avise, an evolutionary geneticist at the University of California at Irvine, has catalogued the array of clumsy flaws and inefficiencies at the fundamental level of the genome. His paper, published this week in the Proceedings of the National Academy of Sciences of the USA1, throws down the gauntlet to advocates of Intelligent design, the pseudo-scientific face of religious creationism. What Intelligent Designer, Avise asks, would make such a botch?

Occasional botches are, by contrast, precisely what we would expect from Darwinian evolution, which is blind to the big picture and merely tinkers short-sightedly to wring incremental adaptive advantage from the materials at hand. Just as in technology, this produces 'lock-in' effects in which strategies that are sub-optimal from a global perspective persist because it is impractical to go back and improve them.

Unintelligent design

Intelligent design does not have to deny that evolution occurs, but it invokes a God who steps in to guide the process, constructing biological devices allegedly too "irreducibly complex" to have been assembled by natural selection, such as (ironically) the eye, or the flagellar motor of bacteria2.

As Avise points out, Intelligent design is problematic in purely theological terms. Were I inclined to believe in an omnipotent God, I should be far more impressed by one who had intuited that a world in which natural selection operates autonomously will lead to beings that function as well as humans (for all our flaws) than by one who was constantly having to make adjustments.

“Occasional botches are precisely what we would expect from Darwinian evolution, which is blind to the big picture.”



But Intelligent design must also confront the issue of theodicy: the evident fact that our world is imperfect. Human free will allegedly absolves God of responsibility for our evil acts — but what of innocent deaths caused by disease or natural disaster? Infelicities in the course of nature were already sufficiently evident in the eighteenth century for philosopher David Hume to imply that God might be considered a "stupid mechanic". And in the early twentieth century, the physician Archibald Garrod pointed out how many human ailments are the result not of God's wrath or the malice of demons but of "inborn errors" in our biochemistry3,4.

Many of these "errors" can now be pinpointed to genetic mutations: at a recent count, around 75,000 of them are disease-linked5. But the "unintelligent design" of our genomes, Avise says, goes well beyond such blemishes.

The ubiquity of introns — sequences that must be expensively excised from transcribed genes before translation to proteins — seems to be a potentially harmful encumbrance. And numerous regulatory mechanisms are needed to patch up problems in gene activity; for example, by silencing or destroying imperfectly transcribed mRNA — the template for protein synthesis. Regulatory breakdowns may cause disease.

Flawed perfection

Why design a genome so poorly that it needs all this surveillance? Why are there so many wasteful repetitions of genes and gene fragments, all of which have to be redundantly replicated in cell division? And why are we plagued by debilitating, chromosome-hopping 'mobile elements' in our DNA?

These design flaws, Avise says, "extend the age-old theodicy challenge, traditionally motivated by obvious imperfections at the levels of human morphology and behavior, into the innermost molecular sanctum of our physical being".

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Avise wisely avers that this catalogue of errors should deter attempts to use religion to explain the minutiae of the natural world and return it to its proper sphere as a source of counsel about how to live.

But his paper equally demolishes the secular tendency to reify and idealize nature through the Panglossian view that natural selection creates "perfect" products, which exerts a dangerous tug in the field of biomimetics. We should be surprised that some enzymes seem indeed to show the maximum theoretical catalytic efficiency6, rather than imagining that this is nature's default condition.

However — although heaven forbid that this should seem to let ID off the hook — it is worth pointing out that some of the genomic inefficiencies Avise lists are still imperfectly understood. We should be cautious about writing them off as 'flaws', lest we make the same mistake evident in the labelling as 'junk DNA' genomic material that seems increasingly to play a biological role. There seems little prospect that the genome will ever emerge as a paragon of good engineering, but we shouldn't too quickly derogate that which we do not yet understand.