I cannot resist being autobiographical. My own first scientific papers, written while I was turning myself from an engineer into a biologist, concerned animal mechanics. Why do primitive flying animals have long tails? Why is the jaw articulation in carnivores level with the tooth row, but in most herbivores above it? Why are the gaits of mammals as they are? Back in 1950, it was hard to get such papers accepted for publication. Editors did not like functional explanations. I had particular difficulties with my paper on gaits, which may have been the first genuine “optimization” paper in biology. To find the optimal gait, the one that would minimize energy expenditure at a given speed, I wrote down a differential equation: (dw/dj=o). The editor, offended by this attempt to sully a respectable biological journal with mathematics, asked “Why don’t you cancel the d’s?” I fear that this story will amuse only some readers, but I want to get it on record.
Since those early days, I have spent much time studying structures and processes which might be thought to raise difficulties for an adaptive view of life—for example, aging, sex, ritualized behavior. As Theodosius Dobzhansky put it, none of these processes makes any sense except in the light of evolution. Essentially Dennett is right: if there are philosophers out there who think that biology can do without functional explanation, they are just wrong.
Two other Gouldian themes, punctuated equilibria, and the non-repeatability of evolution, can be dealt with more briefly. The tale of punctuated equilibria is an odd one. Its factual basis, commonly reported by paleontologists, is that lineages often change very little for millions of years, and then change rather rapidly. When the idea was first put forward by Gould and Niles Eldredge, it was presented as just what one would expect to see if the orthodox view, that species often arise by rapid evolution in small peripheral populations, is indeed accurate. If only they had left the argument there! Their paper would then have been seen as a useful extension of the picture given in Tempo and Mode in Evolution by George Gaylord Simpson, which was the Darwinian orthodoxy when I was a student. Sometimes, however, Gould appears to be saying that the changes, when they occurred, were not the result of natural selection, but of some other process—genetic revolutions, “hopeful monsters” (large mutational changes), or what you will. Since “sudden” in the fossil record means thousands of generations, there is no reason whatever for supposing any such thing.
The non-repeatability of evolution—the idea that if evolution were to happen again from the same starting point, it would not repeat itself—is true, but not new: it is what most scientists have always thought. But what, Dennett asks, is the significance of these various reservations—anti-adaptationism, punctuated equilibria, non-repeatability? The answer, he suggests, is that Gould is trying to escape from an algorithmic explanation of life. Dennett may be right.
The natural selection of replicators—essentially, of nucleic acid molecules—may explain the evolution of animals and plants, but what about humans? We, surely, are more than the product of our genes. Indeed we are, admits Dennett, but it does not follow that we are anything other than the products of an algorithmic process. At this point, he embraces Dawkins’s notion of a meme. A meme can be anything from the limerick about the young man of Belgrave (mutated in the US, I’m told, to a young fellow called Dave) to the doctrine of the Trinity. A meme is an idea that can lodge in a person’s mind, and can be transmitted, in print or by word of mouth, to other minds. In other words, it is a replicator. What is peculiar about humans is that they can hold ideas in their heads, and transmit them to others: they provide an environment in which a new kind of replicator, memes, can evolve. The human mind is another example of a crane. It evolved by natural selection, without need for an intelligent designer. Once evolved, however, it provides a medium in which a new kind of evolution by natural selection can occur, involving a new kind of replicator, the meme.
My uneasiness with the notion of memes arises because we do not know the rules whereby they are transmitted. A science of population genetics is possible because the laws of transmission—Mendel’s laws—are known. Dennett would agree that no comparable science of memetics is as yet possible. His point is a philosophical rather than a scientific one. We see humans as the joint products of their genes and their memes—indeed, what else could they possibly be?—even if we have no predictive science of meme change. Once a human mind capable of harboring memes evolved, a new kind of evolution, cultural evolution, became possible, more rapid by far than genetic evolution.
What is needed for the harboring and transmission of memes? Essentially, it is language. The past thirty years has seen a debate on the nature of language. For Skinner, the ability to learn a language was just an aspect of our general learning ability. For Chomsky and his students, it is a special faculty, both in the sense of being peculiar to humans and of being peculiar to language. Dennett accepts, and I agree, that this argument has been won by Chomsky: there is indeed a special “language organ” that enables children to learn to talk. I see Chomsky, and I think Dennett would agree, as one of the half-dozen commanding intellects of this century.
I therefore find Chomsky’s views on evolution completely baffling. If the ability to learn a language is innate, it is genetically programmed, and must have evolved. But Chomsky refuses to think about how this might have happened. For example, in 1988 he wrote, “In the case of such systems as language or wings, it is not easy even to imagine a course of selection that might have given rise to them.” This is typical of his remarks on evolution. There is, in fact, no difficulty in imagining how wings might have evolved. Language is difficult because it leaves no fossils; it has evolved just once (unlike wings, which have evolved at least four times); and there is an enormous gap between the best that apes, whales, or parrots can do and what almost all humans can do.
Happily, some Chomskian linguists, notably Steven Pinker, are taking up the challenge.2 It is not hard to think of functional intermediates between ape language and human language, but it is hard to decide what were the actual intermediates. Perhaps more interestingly, new kinds of organs—and the language organ is certainly new—do not usually arise from nothing, but as modifications of preexisting organs with different functions. Teeth are modified scales, legs are modified fins, and, after complex transformations, ears are modified parts of the lateral line organs of fish. What was the language organ doing before it acquired its present function?
The question may not be unanswerable. The best chance may lie in genetic analysis. The Canadian linguist Myrna Gopnik has identified one human gene which, if mutated, causes a limited but specific deficiency in grammatical competence.3 There is a real chance that genetic analysis will, in time, reveal the nature and origin of the human language organ, just as it is already revealing how animal form appears during embryological development.
Why does Chomsky not wish to think about evolution? Dennett, who is as puzzled as I am, has an interesting idea. Chomsky, he suggests, would readily accept an explanation of linguistic competence in terms of some general physical law, but not in terms of messy, ad hoc, contingent engineering design, which is the best that natural selection can do. If so, he is not alone in his taste for general, elegant explanations. My friend Brian Goodwin, the developmental biologist, cannot bear the idea that the explanation for development may be a series of ad hoc contrivances, and another friend, the Japanese evolution theorist Motoo Kimura, sadly now dead, once rejected an idea of mine with the words, “It is possible, but it would be so inelegant.” But I fear that the world is inelegant. There is a lesson which Chomsky’s students, if not the great man himself, will have to learn. Science is a unity. Biology cannot ignore chemistry, much as I wish it could; for the same reason, linguistics cannot ignore biology.
One last point before leaving language. In 1989, Pinker and his student Paul Bloom presented a paper at MIT entitled “Natural Language and Natural Selection,” which argued that the origin of the language organ, like that of other organs, must be explained in Darwinian terms. Dennett tells us that it was the “level of hostility and ignorance about evolution that was unabashedly expressed by eminent cognitive scientists on that occasion” that persuaded him that he could no longer put off writing the present book. I am delighted that he was provoked.
Dennett is critical of sociobiology, or at least of its application to humans. He accuses it of “greedy reductionism,” of trying to reduce human behavior too directly to biology. Our behavior is affected by memes as well as by genes, and the attempt to explain it, as biologists explain much of animal behavior, as a direct adaptation ensuring gene transmission is therefore unjustified. However, he is more sympathetic to the new wave of sociobiology represented by evolutionary psychology. The most interesting claim made by evolutionary psychologists is that the mind contains specialized modules that evolved to perform particular tasks.
This is obviously true of that part of the brain concerned with analyzing visual input, and, if Chomsky is right, it is true of language. It has been proposed that there are also modules concerned, for example, with the detection of cheating and with the identification and classification of living organisms. Of course, even if there are such modules, they cannot be completely isolated. In science, as in other fields, progress often depends on seeing analogies between apparently different processes. For example, my own main contribution has been to see the analogies between human games and the things that spiders, trees, and even viruses do. This would not be possible if the mind consisted of isolated modules. Although he is attracted by the notion of modularity, Dennett warns that the mere fact that humans in different societies behave in similar ways cannot be taken as evidence of genetic determination. People may simply be doing what any intelligent being would do in the circumstances: making a forced move in design space, to use his terminology.
A potentially serious challenge to his position is posed by an argument, put forward by Roger Penrose and others, that Gödel’s theorem can be used to show that human intelligence cannot be algorithmic. The argument goes as follows—Gödel proved that there exist, within any non-contradictory mathematical system, some true statements that cannot be proved. Yet human mathematicians can intuit the truth of some such statements. Since anything that can be proved can, in principle, be proved algorithmically, it follows that humans can do something that algorithms cannot. Dennett replies that, although there is no algorithm that can prove a given statement to be true, there may well be algorithms that can suggest statements that are very probably true. Humans, perhaps, use algorithms of the latter kind. Their intuited mathematical truths may just be very good guesses. By analogy, a computer programmed to play chess cannot, with certainty, find the best possible move, but it does find very good moves. Dennett’s argument on this point should be read with care. I am not sure I have understood it correctly, but I like it, partly because I cannot see what else human intelligence could be, other than algorithmic, and partly, perhaps, because while I am rather good at having mathematical intuitions, I have learned that they are sometimes wrong.
Dennett’s last topic is the evolution of morality. Here it is important to distinguish two questions: “How could humans come to have a sense of right and wrong?” and “What is right and what is wrong?” I do not think the first question is all that difficult. I would expect any intelligent organism that lives in groups to evolve an ability to hold beliefs about right behavior, and to be influenced in those beliefs by myth and ritual. We do not only have beliefs: we make contracts. It is worth asking what cognitive equipment is needed to make a contract. At the very least, it requires language and a “theory of mind”: that is, we must be able to perceive other people as beings like ourselves, with minds like ours. Both these qualities are probably unique to humans.
But is there any way in which we can decide, with certainty, which actions are right? Dennett’s view, which I share, is that there is not, unless you hold that some book, for example the Bible, is the word of God, and that human beings are here to do God’s bidding. If a person is simply the product of his or her genetic makeup and environmental history, including all the ideas that he or she has assimilated, there is simply no source whence absolute morality could come. Of course, this does not exempt us from making moral judgments: it only means that we cannot be sure that we are right.
At the start of his book, Dennett says that he aims to persuade us not only that the world is free of skyhooks, but that we can live happily in such a world. In the last two chapters, he tries to deliver on this second promise. He is surprisingly successful. In essence, he says that, no matter how mindless the processes of evolution may be, they have, in fact, produced a world of astonishing diversity and beauty, which we can enjoy, and ought to protect. It is a conclusion that echoes the final words of the The Origin of Species: “…from so simple a beginning, endless forms most beautiful and most wonderful have been, and are being evolved.”
See Pinker's The Language Instinct: How the Mind Creates Language (HarperCollins, 1994), reviewed in these pages, March 23, 1995.↩
Myrna Gopnik, "Impairment of Tense in a Familial Language Disorder," Journal of Neurolinguistics, No. 8 (1994), pp. 109–133.↩
Language and Evolution February 1, 1996