«The Bowerbirds and the Bees: Miller on Art, Altruism and Sexual Selection Catherine Driscoll*† Dept. of Philosophy North Carolina State University ...»
Miller on Art, Altruism and Sexual Selection 1
The Bowerbirds and the Bees: Miller on Art, Altruism and Sexual Selection
Dept. of Philosophy
North Carolina State University
*Many thanks to Stephen Stich and Walter Sinnott-Armstrong for many comments on earlier
drafts of this paper; and to Iris Oved and the participants in the Rutgers graduate seminar on the
Evolution of Cognition for their feedback on some earlier versions of ideas I discuss here.
†Address for correspondence: Department of Philosophy, North Carolina State University, Campus Box 8103, Raleigh NC 27695-8103. Email: firstname.lastname@example.org Miller on Art, Altruism and Sexual Selection 2 The Bowerbirds and the Bees: Miller on Art, Altruism and Sexual Selection Abstract Geoffrey Miller argues that we can account for the evolution of human art and altruism via the action of sexual selection. He identifies five characteristics supposedly unique to sexual adaptations: fitness indicating cost; involvement in courtship; heritability; variability and sexual differentiation. Miller claims that art and altruism possess these characteristics. I argue that not only does he not demonstrate that art and altruism possess these characteristics; one can also explain the origins of altruism via a form of group selection and traits with the five characteristics in terms of a process I call “cultural sexual selection.” Miller on Art, Altruism and Sexual Selection 3 The Bowerbirds and the Bees: Miller on Art, Altruism and Sexual Selection
1. Introduction Explanations of the origins of human psychological and behavioral traits in terms of sexual selection have not been very common in the evolutionary behavioral sciences. Sexual selection is a process by which the sexual choice of individuals and/or the competition between individuals for mates drives the evolution of characters within a population. The question Geoffrey Miller addresses in his book "the Mating Mind" (2000) is whether such a process could account for some of the elements of "human nature" that have eluded other kinds of evolutionary explanations up to this point.
Miller believes that human psychological mechanisms for producing art and/or artistic behavior are very good candidates to be sexual adaptations (i.e. traits present in a population because of the action of sexual selection); he believes the same is true for the more extreme forms of human altruism1 - in particular those that involve making grand and wasteful altruistic gestures that are not easily explained using standard models of reciprocal altruism2 and kin 1 The biological definition of an altruistic act is an act "where an animal behaves in such a way as to promote the advantages of other members of its species not its direct descendents at the expense of its own" (Hamilton, 1963) i.e. altruistic acts involve taking fitness costs for oneself as a consequence of acting to benefit other member(s) of one's species.
2 Reciprocal altruism can be explained as follows: if the participants in any trade of costs and benefits are going to meet more than once, and if the interaction will lead to greater benefits to the recipient than costs to the donor (i.e. if the interaction is non-zero sum), then reciprocal altruism can evolve. If a participant's involvement in any given interaction is dependant on having received cooperation from the other participant in their previous interaction, then altruists who pay back the benefits they have derived from previous interactions are more fit than selfish individuals who do not. The selfish individuals are rapidly excluded from the benefits of altruistic interaction since they do not
selection3 (nepotistic altruism). There are five main characteristics of sexually selected traits that are more or less unique to such traits. Miller claims that art and altruism show many or all of these characteristics, and are therefore likely to be sexual adaptations.
My thesis in this paper is that Miller’s case for the origin of these two traits via sexual selection, although original, is problematic. Miller’s argument faces a variety of different problems, and these fall into three main classes. First, there is the problem of what kinds of traits he has in mind by “art” and “altruism” – are these psychological capacities that humans possess, or certain types of behavior in which human beings engage, or indeed the products of artistic activity(e.g. paintings, sculptures, etc.) as the ‘extended phenotypes” of the artist? Second, it is not clear that art and altruism possess the five characteristics that Miller thinks identify sexually selected traits. Third, Miller’s argument relies on there being no other process that could explain the presence of the five characteristics as well as sexual selection, but there is at least one cultural process that can also reliably generate traits with those characteristics. Finally, it appears from the literature that there is a much better explanation for the origin of altruistic behavior than sexual selection.
In this paper I will proceed as follows. In Section 2 I describe the process of sexual selection. Section 3 will describe Miller’s argument, including the five main characteristics that identify sexually selected traits. Then in Section 4 I will present the problems relating to Miller’s definition of “art” and “altruism”. Section 5 attacks Miller’s claim that art and altruism possess in reciprocal interactions than selfish individuals who cannot.
3 Kin selection occurs where genes for assisting relatives tend to increase themselves - close relatives of an organism that possesses a gene for helping relatives are likely to possess copies of the same genes. Thus an organism O that possess a gene for helping relatives G will tend to increase the survival or reproduction of other copies of G in the
the five characteristics. Section 6 will discuss an important alternative explanation for altruism and offer reasons for thinking this account is better than Miller’s; in Section 7 I will present an alternative explanation for the origins of traits with Miller’s five characteristics in terms of cultural evolution.
Sexual selection is often invoked to explain traits that arise in nature that are strange, extreme or otherwise costly to the organism that possesses them. Sexual selection is a process by which sexual choice or competition for mates among individual animals leads to certain traits increasing in the population; i.e. those traits which make the individuals that possess them more likely to win sexual competitions or to be preferred by members of the opposite sex. Sexual selection's most interesting characteristic is that it can cause a trait T to evolve even where T is otherwise not very fit - i.e. beyond its assistance in the competition for sexual opportunities, T does not help or even inhibits an animal's survival and reproduction. Thus sexual selection is often implicated in the evolution of big, showy, extravagant traits that seem as though they ought to reduce the fitness of the organism that possesses them. An example of such a trait would be the peacock's tail - it is big and showy, and it makes the peacock both more visible to predators and less agile and able to escape those predators. However, peahens like the tail; and this preference drives the tail's evolution.
Sexual selection comes in two main forms: sexual selection by competition for mates and sexual selection by (usually female) choice. I will describe these two, and then explain how the
2.1. Sexual selection by competition Sexual selection by competition occurs in species where members of one sex compete among themselves for access to the other (usually males compete for females). Males that possess traits which allow them to win the sexual competition against other males gain access to more females or to fitter, healthier females than those that do not have these traits; they then pass on these successful traits to their (more numerous or healthier, more likely to survive) offspring.
This can lead to these traits increasing in frequency in the population. A classic example would be the competitions between male red deer, who “battle” each other using their antlers. The winners of these battles – usually the strongest males - gain mating access to herds of females.
2.2. Sexual selection by mate choice Sexual competition by mate choice occurs where the members of one sex choose mates from among the members of the opposite sex. Because females bear the greater part of the burden of reproductive investment they generally are the ones that choose which males to mate with. In species where there is monogamy, males may also choose which females to pair up with;
this can lead to some sexual selection on females as well. Usually these choices take place on the basis of the female's preference for some male trait T; males with T will gain greater access to females than males without T. Therefore T will increase in prevalence in the population.
2.3. Feedback loops and "runaway sexual selection" The way in which sexual selection has the potential to produce the strange evolutionary phenomena I described earlier is via the phenomena of runaway sexual selection. Runaway
female preferences. The phenomenon of runaway sexual selection was described by R. A. Fisher (1930). His point was that sexual preferences are self-reinforcing, because when a female has a preference for a certain male trait, and mates preferentially based on that trait, she passes on both that male trait to her sons, and her own preference for that trait to her daughters, thereby increasing both the representation of the trait in the population and the representation of the preference for that trait. This "feedback loop" can make sexual selection proceed very rapidly.
Runaway sexual selection has particularly noticeable effects where females prefer a trait that comes in degrees and where they prefer more of that trait to less of it. For example, suppose females like elaborate crests, and the more elaborate the crest the better. Every time a new, more extreme version of the trait arises, females choose males with that variant and the feedback loop drives the new version to fixation very quickly. It is this sort of runaway sexual selection that is likely to be responsible for some of the more extreme traits possessed by male animals - for example, the extremely elaborate plumage of male birds of paradise.
So far I have described what sexual selection is supposed to be and some of the ways in which it can operate. I now want to briefly describe a major problem for sexual selection and its potential solution.
As I described earlier, it is clear that in many cases sexual selection is acting against natural selection in that females are choosing traits that would, without the sexual preference, be clearly harmful to the males that possessed them - e.g. the peacock's tail. The problem here is that when females choose traits that may have a negative effect on the males that possess them,
fitness disadvantage. In other words, one could object that surely female choice is also capable of being the target of natural selection, and if so, extreme female choice must surely be selected against. Females that prefer males with traits which do not threaten the male's well being must have sons that are better off in non-sexual ways (and hence will probably live longer to participate in more sexual competitions). Since the mother also creates a feedback loop by passing on sensible preferences to her daughters, her sons have as much sexual success as those males whose mothers choose extreme traits, and they live longer because they are not burdened with a cumbersome sexual adaptation. Thus sensible female preferences must out-compete extreme female preferences. In other words, if we are to explain why extreme and costly traits arise in nature, we need more than merely ordinary sexual choice to be operating.
2.5. The handicap principle Amotz Zahavi (1975) proposed a solution to the problem of female choice. He claimed there was a way in which females who chose extreme traits in their mates could end up producing fitter sons. The idea is that extreme traits are good indicators of the overall fitness of the male that the female is choosing. Although an extreme trait may itself be detrimental to the male's fitness, he can only produce a complex or extreme trait really well if he is otherwise sufficiently genetically and physically sound. Sickly or genetically inferior males do not produce extreme traits or produce extreme traits that are less spectacular. This means that a female can use the quality of an extreme trait as an index of the male's overall genetic or physical health and this is especially useful where there is no other way for a female to determine the overall quality of a male.
traits? If a female chooses a male who has a superficial trait that is fitter - i.e. it is not extreme and costly - she is, in effect, passing on one positive trait to her sons. If a female chooses a male with a really extreme trait, she is passing on multiple positive traits to her sons, because she is choosing a male who has overall higher genetic quality. Extreme traits may individually have high fitness costs, but they are often good indicators of the overall quality of the male the female is choosing - they are good "fitness indicators". Miller claims that art and altruism have evolved as sexual adaptations in humans, as just these sorts of fitness indicator traits. I will now examine how Miller proposes to support this claim.