Princeton University - Council of Science & Technology

POPE PRIZE

Essay 1
The Smartest and the Fastest: Investigating the limits of nature
Charles Graham Wells

Essay 2
Oldfield Mice, Theoretical Biology and the Search for True Love
Sarah Helen Labun

Essay 3
John Horton Conway, John von Neumann Distinguished Professor of Mathematics
Lillian Beatrix Pierce

The Smartest and the Fastest
Investigating the limits of nature

On March 11, 2001, the London Sunday Telegraph reported that geneticists at a lab in India intend to clone the Asiatic cheetah, in hope of preventing the animal's extinction. It's nothing special, I suppose-we have presided over other clonings, and other extinctions. But I find it interesting that we, who are capable of inserting cheetah DNA into a leopard's womb, were careless enough to kill so many cheetahs in the first place. And there is something else that struck me, something about the very fact that we are trying to bring a large carnivore back into the game. I can imagine a time when cats and men were in competition: the cats killed the same grazing ungulates that we might have wanted, and occasionally even killed us. But now we feel safe-so insulated from the jungle world, that, having nearly eliminated a species, we are trying to revive it. It seems that in the competition between brains, and claws, and wings, and teeth, brains have won.

Still, it is shocking how close the cheetah has come to extinction. Cheetah! The world's fastest animal, a perfect arrangement of muscle and bone, an organic land missile. He is four feet long, with another three feet of tail, stands two and half feet at the shoulder, and is lightly built-hardly more than a hundred pounds. He has coarse fur, tan to sandy yellow, with half-inch black spots to break up the long lines of his body, and black streaks to disguise his face. He has loose skin, which bunches and folds over his high shoulders.

Every component is optimized for speed. For example, his paws: other cats have strong, sharp claws, which they use to climb trees and catch prey, and which slide into sheathes when they walk. But claws cost speed. The cheetah could not run with them extended-picture track shoes with four inch spikes-but he could not run with them retracted either, because he would not have adequate traction. Instead, his paws resemble dogs' paws, small pads tipped with blunt nails.

The force of his speed would shatter most bodies, but his is built for it. His short collarbones do not attach to any joint-the impact would crack them-but are buried in knots of muscle. And while horses run with stiff backs, the cheetah's trunk is powerfully elastic; it folds and extends in tandem with her rear legs. He has small teeth, because his large nostrils and nasal ducts do not leave room in the skull for the long roots needed to anchor big teeth.

The result of this specialization is astonishing speed. Ironically, in spite of the cheetah's scarcity, his explosive hunt has become familiar, because he is a star of the Animal Channel. He begins the chase at a trot, and once spotted, gives an accelerated push that propels him ten feet forward. His loose skin stretches taut, and his long tail extends. His back legs, which look awkwardly long when he walks, now stretch out behind him in lean streaks of yellow. His strides span thirty feet, and he takes four per second, so in two and a half seconds he covers one hundred yards. He catches seventy percent of the things he chases, twice what lions manage.

But the cheetah has not been seen in India for over fifty years. There are only 250 Asiatics left in the world, and fewer than 5,000 African cheetahs. Now, we are not fully responsible: cheetah cubs are vulnerable to predators, because their parents cannot protect them. And diseases hit the species hard, because it is genetically homogenous, probably as a result of a population bottleneck sometime in the past. Still, we have made a significant contribution to the cheetah's decline. We have been hunting the cat since before the time of Christ. The Mogul emperor Akbar is said to have kept thousands, and in India cheetahs were used to hunt blackbuck as late as the last century. In the fight to survive, we have beaten the cheetah. But to an observer 100,000 years ago it might not have been obvious that this would happen. After all, it seems that if humans wandered the bush, we would be at the top of a big cat's menu: 100-plus pounds-a respectable meal, laughable speed, nonexistent defense. How did we outrun the fastest animal on Earth?

We have sacrificed speed and strength to pay for our brain, which, in terms of oxygen consumption, is an expensive organ. Now, a brain is a mass of neurons, and it is easy to explain how a mass of neurons evolves. It evolves in exactly the same way the cheetah's paws evolved: random mutations of the genotype prove helpful, and the animal survives to reproduce. What is hard is to explain exactly why our mass of neurons has proved to be so helpful. The cheetah's paws are obvious enough, but what exactly is our big brain doing for us?

Daniel Dennett writes in Consciousness Explained, "the fundamental purpose of brains is to produce future…brains are, in essence, anticipation machines" (177). Of course, it is possible to survive without an anticipation machine: trees do it all the time. But it can be helpful to have some way to respond to the environment. With the most rudimentary neurons, clams, for example, can close when poked. As the number of neurons gets bigger, and the neurons connect to more sophisticated sensory organs, they can begin to trigger a muscle at the mere approach of a poker-no contact necessary. As number of neurons increases further, the animal can have such detailed awareness of its environment that it reaches a state we call consciousness. Now, it has always seemed strange that the magical qualities of being awake can be explained in terms of neural connections, and the mystery of this prompted philosophers to postulate a sort of ethereal mind stuff. But many things are both strange and true. It is strange that ordered layers of silicon are all that constitute modern computers, but we should probably accept it. Do we really want to claim that, once we slide the cover on, there appears a ghost in the machine?

It is the brain that makes us conscious, but it is not consciousness that makes us unique-cheetahs are conscious too. To make the question as precise as possible, we might say this: chimpanzees are genetically closer to humans than they are to gorillas, and they shared a common ancestor with us only 6 million years ago. But the chimpanzee's role in the natural world is much closer to the cheetah's role than to ours. What, then, is the difference between human beings and chimpanzees? Hint: size matters. After men split from chimps, brain sizes on our branch of the evolutionary tree grew four times as large as theirs. It is controversial exactly what caused this. It does seem clear that the growth was largely complete 150,000 years ago, which means that it could not have been driven by the development of language, because it predated language.

If the cause is obscure, the result is clear: our bigger brains allowed us to take advantage of what James Baldwin identified in 1896 as "a new factor in evolution," a factor which, unlike familiar Darwinian evolution, does not depend on genetic change. Suppose you have a small toolbox, with only a few tools. When you come upon a problem that you cannot fix with the tools you have, you must make a new tool. This takes a long time. If you must build the tool using Darwinian evolution-natural selection acting on genetic mutations-then it may take millions of years. But if you have a large toolbox with many tools, you can solve unfamiliar problems by using the tools you already have in new ways. In the context of evolutionary time, this happens instantaneously. The human brain is the well-stocked toolbox. It contains such a complex network of neurons that it can accommodate radical changes in our knowledge and cognitive abilities without any changes in our genome. Thus the brain of Homo sapiens did not grow as he learned to talk about the weather. There was no increase in skull size, no significant genetic change. But there were physical changes: neurons in his brain began to connect in new ways. Thus it was the brain's complexity, the sheer number of neurons, that made it flexible, and flexibility allowed it to expedite its own evolution. And this flexibility is still with us. Dennett again: "People are extraordinarily good at overcoming brain damage, and it is never a matter of 'healing' or the repair of damaged circuits. Rather, they discover new ways of doing the old tricks" (197-198).

Of course, this does not explain how physical changes which are not expressed in the genome can be passed to daughter generations. Our children do not inherit our calluses; why do they inherit our thoughts? The short answer is, each generation shares its tricks with the next. French children hear French spoken, and their brains respond: neural connections develop so that the child begins to process, and eventually produce, the language. And the brains of French children are measurably different from those of English children. It is highly plausible that this is the way language developed in the first place: the hardware was intact, and when a person or group of people learned a helpful way to use the hardware, they passed it on to their neighbors and children. The helpful uses accumulated until they became a mature language.

The general term for this sort of skill development is cultural evolution, and again, because it does not depend on natural selection of genetic mutations, it happens extremely quickly. Stephen Jay Gould writes, "The obvious main difference between Darwinian evolution and cultural change clearly lies in the enormous capacity that culture holds-and nature lacks-for explosive rapidity….Everything that we have accomplished in the unmeasurable geological moment of the last ten thousand years…has been built upon the capacities of an unaltered brain." Thinking that 10,000 years sounded a bit conservative, I asked Stanford biologist Paul Ehrlich what would happen if we plucked a baby girl out of the distant past, and dropped her into a family in suburban New Jersey. He replied, "I suspect that if you plucked one from as long ago as 80,000 years, and maybe much longer, she'd grow up to be indistinguishable from a random person from Plainsfield."

It is our universal science fiction fear that mankind will create a robot which can improve itself, ultimately taking power away from us. It's funny we fear that, because in the natural world man is that robot. Intelligence has trumped the other weapons: it is the claw that sharpens itself. But it can be more than a claw, and we can be more than destroyers. It is unclear whether we will bring the cheetah back into the world. Perhaps we can't. But we know that even failure can be hopeful, because we will learn from our mistakes. We have to, as the cheetah has to run. There is no difference: it's the steady drive of nature.

Bibliography

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Ehrlich, Paul. E-mail to author. 1 May 2002.

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