Good Science Writers: Richard Lewontin

 
Richard "Dick" Lewontin (1929 - ) is Alexander Agassiz Research Professor at Harvard University (Boston, USA). He is a well-known geneticist and the discoverer of extensive variation in organisms at the molecular level, with John Hubby [Citation Classic]. (See The Cause of Variation in a Population.)

Lewontin is also one of the authors of the textbook Modern Genetic Analysis. It's impossible to tell who wrote what in that textbook but I strongly suspect that Lewontin is responsible for the material on Random Genetic Drift and Population Size that I quoted last year.

He is the co-author (with Stephen Jay Gould) of The spandrels of San Marco and the Panglossian paradigm: a critique of the adaptationist program, one of the most important papers in evolutionary biology [Citation Classic]. If you haven't carefully read that paper then you should do so right now.

In addition to his genetics textbook, Lewontin has also written books on The genetic basis of evolutionary change (1974), Human diversity (1995) and The Triple Helix: Gene, Organism, and Environment (2000). He is probably best known for his crusade against genetic determinism as described in Not in Our Genes: Biology, Ideology and Human Nature (with Steven Rose and Leon Kamin) as well as other books. Like several of his colleagues, Lewontin is a frequent contributer to the New York Review of Books and some of his best work has been republished in It Ain't Necessarily So: The Dream of the Human Genome and Other Illusions (2000).

Richard Dawkins did not choose anything from Richard Lewontin for The Oxford Book of Modern Science Writing. I can't imagine why.

The first selection is from Biology as Ideology: The Doctrine of DNA (1991) based on a series of lectures he gave at the University of Toronto in 1990. I was there.

The subject is sociobiology and genetic determinism. He has just finished explaining why there's no such thing as universal human nature—at least not the sort that is postulated by evolutionary psychologists and sociobiologists.

The final step in the sociobiological argument is to say that the genes we possess for universal human nature have been established in us through evolution by natural selection. That is, once upon a time human beings varied genetically in the degree to which they were aggressive, xenophobic, indoctrinable, male dominant, and so on, but those individuals who were most aggressive or most male dominant left more offspring, so the genes that were eventually left in us as a species were the ones that now determine those traits. The argument of natural selection seems a fairly simple and straightforward one for some kinds of traits. For example, it is argued, the more aggressive of our ancestors would leave more offspring because they would swoop down on the less aggressive and eliminate them. The more entrepreneurial would have appropriated more resources in short supply and starved out the wimps. In each of these cases, it is easy to make up a plausible story that would explain the superior reproductive abilities of one type over another.

There are, however, some traits that are said to be universal and that do not lend themselves so easily to this story of individual reproductive advantage. An example, and one that is discussed a great deal by sociobiologists, is altruistic behavior. Why should we be cooperative under some circumstances, and why should we sometimes give up what appear to be immediate advantage for the benefit of others? To explain altruism, sociobiologists advance the theory of kin selection. Natural selection for a trait does not require that individuals possessing it leave more offspring but only that the genes coding the trait be represented in larger numbers in future generations.

There are two ways to increase the representation of one's genes in future generations. One is to leave more offspring. The other is to arrange that even if one does not leave more offspring, one's relative's do so, since close relatives share genes. So, a person could sacrifice his reproduction completely, provided his brothers and sisters left many more children. Thus, his kind of genes would increase indirectly through his relatives and, in this indirect way, he would leave more offspring. An example of this phenomenon is the occurrence of "helpers at the nest" in birds, in which it is said that nonreproductive birds help out their close relatives, who are then able to raise more than the ordinary number of offspring and in the end more family genes are left. To make kin selection work, a sufficient number of excess offspring must be left by relatives. For example, if an individual gives up its own reproduction, its brothers and sisters must have twice as many offspring as ordinarily, but one can at least tell a story that might make this plausible.

We are then left with those traits that do not even benefit relatives differentially, for example, a general altruism toward all members of the species. Why are we good to strangers? For this phenomenon, the sociobiologist provides the theory of "reciprocal altruism." The argument is that even if we are unrelated, if I do you a favor that costs me something, you will remember that favor and reciprocate in the future, and by this indirect path I will succeed in advancing my own reproduction. An example often given is that of a drowning person. You see someone drowning and jump in to save that person even at the risk of your own life. In the future, when you are drowning, the person whose life you have saved will remember, and save you in gratitude. By this indirect path you will increase your own probability of survival and reproduction over the long run. The problem with this story is, of course, that the last person you would want to depend on to save you when you are drowning is someone whom you had to save in the past, since he or she is not likely to be a strong swimmer.

The real difficulty with the process of explanation that allows direct advantage, or kin selection, or reciprocal altruism when one or the other is useful in the explanation, is that a story can be invented that will explain the natural selective advantage of any trait imaginable. When we combine individual selective advantage with the possibility of kin selection and reciprocal altruism, it is hard to imagine any human trait for which a plausible scenario for its selective advantage could not be invented. The real problem is to find out whether any of these stories is true. One must distinguish between plausible stories, things that might be true, and true stories, things that actually have happened. How do we know that human altruism arose because of kin selection or reciprocal altruistic selection? At the very minimum, we might ask whether there is any evidence that such selective processes are going on at the present, but in fact no one has ever measured in any human population the actual reproductive advantage or disadvantage of any human behavior. All of the sociobiological explanations of the evolution of human behavior are like Rudyard Kipling's Just So stories of how the camel got his hump and how the elephant got its trunk. They are just stories. Science has turned into a game.

The second example is from a review of Darwinism Defended: A Guide to the Evolution Controversies by Michael Ruse. It was first published in The New York Review of Books on June 16, 1983 and reprinted in It Ain't Necessarily So: The Dream of the Human Genome and Other Illusions.

If Darwin's revolution was not in proclaiming evolution as a fact, then it must have been in his theory of its mechanism. And what was that theory? Why, "natural selection," of course, which then makes the theory of natural selection the very essence of Darwinism and any doubt about the universal efficacy of natural selection anti-Darwinian. There is a form of vulgar Darwinism, characteristic of the late nineteenth century and rejuvenated in the last ten years, which sees all aspects of shape, function, and behavior of all organisms as having been molded in exquisite detail by natural selection—the greater survival and reproduction of those organisms whose traits make them "adapted" for the struggle for existence. This Panglossian view is held largely by functional anatomists and comparative physiologists who, after all, make a living by explaining what everything is good for, and by sociologists who are self-consciously trying to win immortality by making their own small revolution. Evolutionary geneticists, on the other hand, who have spent the last sixty years in detailed experimental and theoretical analysis of the actual process of evolutionary change, and most epistemologists take a more pluralistic view of the forces driving evolution.

An occasional philosopher has allied himself or herself with the "adaptationists," who give exclusive emphasis to natural selection., and one such, Michael Ruse, makes a characteristic presentation in Darwinism Defended. Darwinism, the representative of objective modern science, is under ideologically motivated attack. Professor Ruse is alarmed: "'Darwinism,' as I shall refer to Darwin-inspired evolutionary thought, is threatened from almost every quarter." Well, not from every quarter, just the right and left flanks, it seems. First, the fundamentalists, supported by Ronald Regan, make a know-nothing assault from the right. No sooner have real evolutionists wheeled to face this attack than they are fallen upon by subversive elements from the left, "biologists with Marxist sympathies" and their "fellow travelers" among philosophers who argue "that any evolutionary theory based on Darwinian principles—particularly any theory that sees natural selection as the key to evolutionary change—is misleadingly incomplete."

Onto the field, mounted upon his charger perfectly adapted for the purpose, with weapons carefully shaped by selection to spread maximum confusion among the enemy, not to mention innocent civilians, comes Professor Ruse, "trying to rescue ... from the morass into which so many seem determined to drag them," "Darwin's life and achievements." In all fairness to Professor Ruse, he did not invent this version of events. The theory that evolutionary science is being brutally beaten and cut with crosses, hammers, and sickles made its first appearance in E.O. Wilson's On Human Nature as the only plausible explanation he could imagine for the failure of sociobiology to achieve instant, universal, and lasting adherence. The situation of evolutionary theory, however, is rather more complex and more interesting than Professor Ruse's Manichaean analysis suggests....

What vulgar Darwinists fail to understand, however, is that there is an asymmetry in Darwin's scheme. When adaptation is observed, it can be explained by the differential survival and reproduction of variant types being guided and biased by their differential efficiency or resistance to environmental stresses and dangers. But any cause of differential survival and reproduction, even when it has nothing to do with the struggle for existence, will result in some evolution, just not adaptive evolution.

The Panglossians have confused Darwin's discovery that all adaptation is a consequence of variational evolution with the claim that all variation evolution leads to adaptation. Even if biologists cannot, philosophers are supposed to distinguish between the assertion that "all x is y" and the assertion that "all y is x," and most have. This is not simply a logical question but an empirical one. What evolutionary geneticists and developmental biologists have been doing for the last sixty years is to accumulate a knowledge of a variety of forces that cause the frequency of variant types to change, and that do not fall under the rubric of adaptation by natural selection. These include, to name a few: random fixation of nonadaptive or even maladaptive traits because of limitations of population size and the colonization of new areas by small numbers of founders; the acquisition of traits because the genes influencing them are dragged along on the same chromosome as some totally unrelated gene that is being selected; and developmental side effects of genes that have been selected for some quite different reason.

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[Photo credit: The photograph of Richard Lewontin is from (Photographs of Participants in the Molecular Evolution Workshop)]