Read Darwin's Dangerous Idea Online
Authors: Daniel C. Dennett
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might evolve—a "prediction" stunningly confirmed by the subsequent stud-displays, territoriality, and the like in nonhuman species should be tarred ies of the amazing South African naked mole rats (Sherman, Jarvis, and with the same brush as the more flagrant oversteppers in human sociobiology Alexander 1991). This was such an astonishing triumph of adaptationist is both a miscarriage of justice and a serious misrepresentation of science.
reasoning that it deserves to be more widely known. As Karl Sigmund But neither "side" has done its duty. Unfortunately, the siege mentality has describes it, Hamilton's ideas
made the best of the sociobiologists somewhat reluctant to criticize the shoddy work of some of their colleagues. Though Maynard Smith, Williams, led to a most remarkable discovery when, in 1976, the American biologist Hamilton, and Dawkins can often be found in print firmly setting aright R. D. Alexander lectured on sterile castes. It was well known that these various innocent flaws in arguments and pointing out complications—in existed for ants, bees, and termites, but not for any kind of vertebrate.
short, making the corrections that are the normal topics of communication in Alexander, in a kind of thought experiment, toyed with the notion of a all science—they have largely eschewed the deeply unpleasant task of mammal able to evolve a sterile caste. It would, like the termites, need an pointing out more egregious sins in the work of those who enthusiastically expandable nest allowing for an ample food supply and providing shelter misuse their own good work. Donald Symons (1992 ) is a bracing exception, from predators. For reasons of size, an underbark location [like that of the however, and there are others. I will point to just one
major
source of bad presumed insect ancestors of termites] was no good. But underground
burrows
replete with large tubers would fit the bill perfectly. The climate thinking that is ubiquitous in human sociobiology, and is seldom carefully should be tropical; the soil ( more than a hint of Sherlock Holmes here!) addressed by sociobiologists themselves, perhaps because Stephen Jay Gould heavy clay. An ingenious exercise in armchair ecology altogether. But after has made the point in criticism, and they would hate to concede that he is his lecture, Alexander was told that his hypothetical beast did indeed live right about anything. He is right about this point, and so is Philip Kitcher in Africa; it was the naked mole rat, a small rodent studied by Jennifer (1985b), who develops the criticism in much more detail. Here is Gould's Jarvis. [Sigmund 1993, p. 117.]
version, which is a little hard to understand. (At first, I didn't see how to read it sympathetically, and had to ask Ronald Amundsen, an excellent Naked mole rats are surpassingly ugly and strange, a thought experiment philosopher of biology, to explain to me what Gould was getting at. He of Mother Nature's to rival any of the fantasies of philosophy. They are succeeded.)
genuinely eusocial. The single queen mole rat is the sole female breeder, and she keeps the rest of the colony in line by releasing pheromones that suppress The standard foundation of Darwinian just-so stories does not apply to the maturation of the other females' reproductive organs. Naked mole rats are humans. That foundation is the implication: if adaptive, then genetic—for coprophagous—they regularly eat their own feces—and when the the inference of adaptation is usually the only basis of a genetic story, and grotesquely swollen pregnant queen cannot reach her own anus, she begs Darwinism is a theory of genetic change and variation in population.
feces from her attendants. (Had enough? But there's much, much more,
[Gould 1980c, p. 259]
highly recommended to all whose curiosity exceeds their squeamish-ness.) A bounty has been learned from the study of naked mole rats, and other What does this mean? Gould is not saying, as he may seem at first to be nonhuman species, using the techniques of Darwinian reverse engineering—
saying, that adaptationist inference does not apply to humans. He is saying using adaptationism, in other words—and there is surely more to come. E. O.
that since in the case of humans ( and only humans ) there is always
another
Wilson's own important work on social insects (1971) is deservedly world possible source of the adaptation in question—namely culture—one cannot famous, and there are literally hundreds of other fine animal sociobiologists.
so readily
infer that there has been genetic evolution for the trait in question.
(See, e.g., the classic anthologies, Clutton-Brock and Harvey 1978, Barlow Even in the case of nonhuman animals, the inference from adaptation to and Silverberg 1980, King's College Sociobiology Group 1982.) genetic basis is risky when the adaptation in question is not an anatomical Unfortunately, they all work under a cloud of suspicion, raised by the feature but a behavioral pattern which is an obviously Good Trick. For then escalation of greedy claims by a few human sociobiologists (through their there is another possible explanation: the general
nonstupidity
of the species.
megaphones, as Kitcher suggests), which is then echoed by the escalation of As we have seen so often, the more obvious the move, the less secure the blanket condemnations from their opponents. This really is an unfortunate inference that it has to have been copied from predecessors—specifically fallout, for, as in any other legitimate area of science, some of this work is carried by the genes. Many years ago, I played my first computer "video great, some is good, some is good but false, and some is bad— but none of it game" at the AI Lab at
is evil. That serious students of mating systems, courtship 486 ON THE ORIGIN OF MORALITY
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MIT: it was called Maze War, and more than one person could play it at once, biologists as signs of a special "instinct," when in fact it was just their each at a separate terminal linked to a central time-sharing computer. On the general intelligence that led them again and again to hit upon the same bright screen you saw a simple perspective line drawing of a maze, in which you, idea. The problem of interpretation for
Homo sapiens
is multiplied many the viewer, were situated. Corridors could be seen up ahead leading off to left times over by the fact of cultural transmission. Even if some individual and right, and by pressing keys on the keyboard you could move forward and hunters are not bright enough to figure out for themselves that they should back, or turn ninety degrees to the left or the right. Another key on the throw the pointy end first, they will be told to do so by their peers, or will keyboard was the trigger of your gun, which fired straight ahead. All the just notice their practice, and will appreciate the results immediately. In other other players were in the same virtual maze, wandering around, looking for words, if you are not totally idiotic, you don't need a genetic basis for any someone to shoot, and hoping not to be shot. If one of the other players adaptation that you will pick up from your friends in any case.
crossed your path, he would show up as a simple cartoon figure, whom you It is hard to believe that sociobiologists can make the mistake of ignoring would hope to shoot before it turned, saw you, and shot you. After a few this omnipresent possibility, but the evidence is striking that they have done minutes of frantic play, in which I was "shot" from behind several times, I so, again and again ( Kitcher 1985 )• Many instances could be listed, but I will found my mounting paranoia so uncomfortable that I sought relief: I found a concentrate on a particularly visible and well-known case. Although E. O.
cul-de-sac in the maze, backed myself into it, and just sat there, relatively Wilson (1978, p. 35) states clearly that the human behaviors to be accounted calmly, with my finger on the trigger. It struck me then that I had adopted the for by specific genetic hypotheses should be the "least rational of the human policy of a moray eel, patiently waiting in its well-protected hole for repertoire— In other words, they should implicate innate, biological something strike-worthy to swim by.
phenomena that are the least susceptible to mimicry by culture," he goes on Now, does my behavior on this occasion give us any reason to suppose (pp. 107ff.) to claim, for instance, that the evidence of
territoriality
in all there is a genetic predisposition to moray-eel behavior in
Homo sapiens?
Did human cultures (we human beings like to call a bit of space our own) is clear the stress of the occasion dredge up some ancient policy, lying dormant in proof that we, like very many other species, have a genetic predisposition my genes since the days when my ancestors were still fish? Of course not.
wired in at birth for the defense of territory. That may be true—in fact, it The strategy is just too obvious. It felt like a forced move, but it was at least a would not be at all surprising, since many species manifestly do exhibit innate Good Trick. We would not be surprised to find Martians backing themselves territoriality, and it is hard to think of what force there might be to remove self-protectively into Martian caves, and the likelihood that Martians had such a disposition from our genetic makeup. But the ubiquity of territoriality morays for ancestors would presumably not be adjusted upwards from zero in human societies is
by itself no
evidence at all for this, since territoriality by the discovery. It is true that I am distantly related to moray eels, but the makes so much sense in so many human arrangements. It is, if not a forced fact that I found this strategy in this environment is surely just a matter of its move, close to it.
obvious excellence, given my needs and desires and my own assessment of The very considerations that in other parts of the biosphere count
for
an my limitations at the time. This illustrates the fundamental obstacle—not explanation in terms of natural selection of an adaptation—manifest utility, insuperable, but much larger than is commonly acknowledged—to inference obvious value, undeniable reasonableness of design—count
against
the need
in human sociobiology: showing that a particular type of human behavior is for any such explanation in the case of human behavior. If a trick is that good
,
ubiquitous or nearly ubiquitous in widely separated human cultures goes
no
then it will be routinely rediscovered by every culture, without need of either
way at all
towards showing that there is a genetic predisposition for that genetic descent or cultural transmission of the particulars.11 We saw in particular behavior. So far as I know, in every culture known to chapter 12 that it is the prospect of convergent cultural evolution—
anthropologists, the hunters throw their spears pointy-end-first, but this reinventing the wheel—that plays havoc with our attempts to turn memet-ics obviously doesn't establish that there is a pointy-end-first gene that into a science. The same difficulty besets all attempts to infer genetic approaches fixation in our species.
Nonhuman species can exhibit a similar, if reduced, capacity to reinvent the wheel, even though they lack culture. Octopuses are remarkably intel-11. A useful exercise when considering any such case is to imagine creating a roomful of ligent, and although they show no signs of cultural transmission, they are roughly rational robots ( smart, but with no genetic ancestry at all) and asking yourself if smart enough so that we should not be surprised to discover them individ-they would soon settle into the behavior in question. (If the case is complex, a computer ually hitting upon lots of Good Tricks that had never been posed as specific simulation should be used, as a prosthetic guide to your imagination.) If so, it is not so surprising that human beings everywhere do it, too, and it probably has nothing to do problems to their ancestors. Any such uniformity might be misread by with their primate heritage, their mammalian heritage, even their vertebrate heritage.
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factors from cultural commonalities, and for the same reason. But, although The first and the last, obviously, the same as in the first problem. Why is one Wilson has sometimes noted this problem, at other times he forgets: setting so much easier than the other? Perhaps, you may think, it is the abstractness of the first, the concreteness of the second, or the familiarity of The similarities between the early civilizations of Egypt, Mesopotamia, the second, or the fact that the second involves a conventional rule, not a India, China, Mexico, and Central and South America in these major fea-regularity of nature. Literally hundreds of Wason card-sorting tests have been tures are remarkably close. They cannot be explained away as the products administered to subjects, in hundreds of variations, testing these and other of chance or cultural cross-fertilization. [Wilson 1978, p. 89]
hypotheses. The performance of subjects on the tests varies widely, depending on the details of the particular test and its circumstances, but a We need to look at each remarkable similarity in turn, to see if any of them survey of the results leaves no doubt at all that there are settings that are hard
needs
a genetic explanation, for, in addition to cultural cross-fertilization for almost all groups of subjects, and others that are easy
for the same
(cultural descent) and chance, there is the possibility of reinvention. There
subjects.
But a riddle remained, reminiscent of the riddle of the two black
may
be specific genetic factors operating in many or all these similarities, boxes: what exactly was it about the hard cases that made them hard—or (a but, as Darwin stressed, the best evidence will always be idiosyncrasies—
better question) what was it about the easy cases that made them easy?
quirky homologies—and no-longer-rational survivals. The most compelling Cosmides and Tooby (e.g., Barkow, Cosmides, and Tooby 1992, ch. 2 ) came cases of this sort are currently being uncovered in the marriage of socio-up with an evolutionary hypothesis, and it is hard to imagine this particular biology and cognitive psychology recently going by the name of evolutionary idea occurring to anyone who wasn't acutely aware of the possibilities of psychology (Barkow, Cosmides, and Tooby 1992 ). Highlighting a single case Darwinian thinking: the easy cases are all cases that are readily interpreted as will provide a useful contrast between good and bad uses of Darwinian tasks of patrolling a social contract, or, in other words, cheater detection.