Running with the Pack by Mark Rowlands Page B

sort of thing I am. But what if it yields no such thing? What if, instead, my biological history reveals me to be a confused melange of many different things, and the resulting whole only barely viable and coherent? Sometimes people have the idea that if evolution comes up with something — arses, legs, feet and so on — then whatever this is will be perfectly designed for the job at hand. This forgets that evolution is not so much life’s architect as its handyman; a handyman of dubious competence and numerous mistakes who, in addition, finds himself working for a penny-pinching client. He can slap a bit of paint on here, slap a bit of paint on there. But he is never allowed to tamper significantly with the existing structure. That’s the position evolution always finds itself in. The penny-pinching client is known as survival. You tamper too much with the existing structure — an extant creature — then survive is precisely what it is not going to do. The hurricane that is life is going to make short work of temporary scaffolding put in place while major structural changes are being made. The changes must always be small: gradual accretion of the minor is the game.
    So, for example, evolution is presented with a fish. It used to swim happily in the ocean, but current vicissitudes of the environmental situation suggest that spending long periods of time lying camouflaged in the sand might be a good policy to adopt. So the fish lies on its side and gradually, for purposes of easy camouflaging, becomes flatter and flatter. What do you do about the eye, the one that lies buried in the mud all day? It is of no use where it is. And all things beingequal — which, in the grand evolutionary scheme of things, they hardly ever are — it would be better if the fish had two eyes it could use to watch for predators and prey. So evolution has two options. The first: develop a new eye. But that will cost you. Lots of bodily and neural resources have to be put into that strategy. The second: deploy the unused eye that you’ve already got. Much cheaper. And so that is what evolution did. The grotesquely twisted features of the flatfish’s face are testimony to its evolutionary history and to this parsimonious solution embodied in it. The eye that used to reside on the ventral side of a fish that swam for a living now twists around and relocates to what is now the dorsal side of a fish that spends most of its time in the sand. Evolution works like this. No one ever gives it a blank slate; it can only tinker with whatever is already there.
    So we have to assume that there was an arboreal creature that, presumably due to the affordances or exigencies of environmental circumstance, began to spend more and more time on hazardous, but potentially profitable, terrestrial journeys. No one really knows why this was. Some speculate that the sorts of food offered by trees — leaves, sometimes fruit — no longer provided adequate sustenance. Others argue that we simply became too big for trees to offer us adequate protection from predators. The sorts of branches that could bear our weight would also support theirs. But, for whatever reason, a niche opened up that afforded opportunities for an ape willing to travel overland. At first living on the edge of riparian woodlands, our hominin ancestors gradually expanded their range. In this gradual expansion, those of our ancestors with bigger, more powerful legs — and what good are big legs without the big arse that powers them and provides ballast — survived at greater rates than those with weaker legs andsmaller arses. And so the gene for a big arse multiplies and is passed down to us today.
    But here is the snag. The big arse is still the point of connection between two essentially simian legs, on the ends of which are two essentially simian feet. Evolution is a handyman, not an architect. It has to work with what it is given. Admittedly, it has