On the benefits of Mutual Restraint.
-Richard Dawkins, The Greatest Show on Earth
“In a typical mature forest, the canopy can be thought of as an aerial meadow, just like a rolling grassland prairie, but raised on stilts. The canopy is gathering solar energy at much the same rate as a grassland prairie would. But a substantial portion of the energy is ‘wasted’ by being fed straight into the stilts, which do nothing more useful than loft the “meadow” high in the air, where it picks up exactly the same harvest of photons as it would –at far lower cost– if it were laid flat on the ground.
And this brings us face to face with the difference between a designed economy and an evolutionary economy. In a designed economy there would be no trees, or certainly no very tall trees: no forests, no canopy. Trees are a waste. Trees are extravagant. Tree trunks are standing monuments to futile competition- futile if we think in terms of a planned economy. But the natural economy is not planned. Individual plants compete with the plants, of the same and other species, and the result is that they grow taller and taller, far taller than any planner would recommend. Not indefinitely taller, however. There comes a point when growing another foot taller, although it confers a competitive advantage, costs so much that the individual tree doing it actually ends up worse off than its rivals that forgo the extra foot. It is the balance of costs and benefits to the individual tree that finally determines the height to which trees are pressed to grow, not the benefits that a rational planner could calculate of the trees as a group. And of course the balance ends up at a different maximum in different forests. The Pacific coast redwoods have probably never been exceeded.
Imagine the fate of a hypothetical forest- let’s call it the Forest of Friendship – in which, by some mysterious concordant, all the trees have somehow managed to achieve the desirable aim of lowering the entire canopy to 10 ft high instead of 100 ft. From the point of view of a planned economy, the Forest of Friendship is more efficient as a forest than the tall forests with which we are familiar, because resources are not put into producing massive trunks that have no purpose apart from competing with other trees.
But now, suppose one mutant tree were to spring up in the middle of the Forest of Friendship. This rogue tree grows marginally taller than the agreed norm of 10 feet. Immediately, this mutant secures a competitive advantage. Admittedly, it has to pay the cost of the extra length of trunk. But it is more than compensated, as long as all other trees obey the self-denying ordinance, because the extra photons gathered more than pay the extra cost of lengthening the trunk. Natural selection therefore favors the genetic tendency to break out of the self-denying ordinance and grow a bit taller, say to 11 feet. As the generations go by, more and more trees break the embargo on height. When, finally, all the trees in the forest are 11 feet tall, they are all worse off than they were before: all are paying the cost of growing the extra foot. But they are not getting any extra photons for their trouble. And now natural selection favors any mutant tendency to grow to, say 12 feet. And so the trees go on getting taller and taller. Will this futile climb towards the sun ever come to an end? Why not trees a mile high, why not Jack’s beanstalk? The limit is set at the height where the marginal cost of growing another foot outweighs the gain in photons from growing that extra foot.
We are talking individual costs and benefits throughout this argument. The forest would look very different if its economy had been designed for the benefit of the forest as a whole. In fact what we actually see is a forest in which each tree species evolved through natural selection favoring individual trees that out-competed rival trees a mile high, whether of their own or another species. Everything about trees is compatible with the view that they were not designed …”