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Miller on Art, Altruism and Sexual Selection 1
The Bowerbirds and the Bees: Miller on Art, Altruism and Sexual Selection
Catherine Driscoll*†
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: [email protected]
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
reciprocate, while altruists can continue to benefit. This is because they receive more benefit overall from engaging
Miller on Art, Altruism and Sexual Selection 4
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
O's relatives.
Miller on Art, Altruism and Sexual Selection 5
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.
2. What is sexual selection?
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
process of runaway sexual selection can drive traits to surprising extremes.
Miller on Art, Altruism and Sexual Selection 6
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
sexual selection occurs because there is, in effect, a feedback loop between male traits and
Miller on Art, Altruism and Sexual Selection 7
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.
2.4. The problem of female choice
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,
they pass on those negative traits to their sons; their preferences therefore give their sons a
Miller on Art, Altruism and Sexual Selection 8
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.
So why do females that choose extreme traits out-compete females that choose sensible
Miller on Art, Altruism and Sexual Selection 9
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.
3. Miller’s argument
Miller identifies himself as an evolutionary psychologist. Evolutionary psychologists try
to detect adaptations - traits that are present in the population due to the past action of natural
selection - by looking for two basic sets of characteristics in the traits which they are interested
in accounting for. Generally, evolutionary psychologists look for good design in psychological
mechanisms (Cosmides and Tooby 1987, Tooby and Cosmides 1992). When they find good
design in a trait T, evolutionary psychologists will argue that they have good evidence that T is
an adaptation. The reason is that natural selection is the process most likely by far to produce
good design in traits. In other words evolutionary psychologists are making an argument to the
best explanation; that natural selection is the best explanation for traits that are optimal or welldesigned.
Miller is using a similar sort of strategy in his argument that art and altruism are sexual
adaptations. Traits with a certain suite of characteristics are most likely to have been produced by
sexual selection; when we find those characteristics in a trait we have some good reason to think
Miller on Art, Altruism and Sexual Selection 10
that the trait in question was produced by sexual selection (Miller, 2000, p.132-3). Sexual
selection produces different sets of characteristics in the traits it acts upon than does standard
natural selection. In his book, Miller identifies five central characteristics that he thinks are
unique to sexually selected traits. These are as follows: 1) implication in courtship, since such
involvement is necessary if the trait is to be used as a criterion for mating decisions; 2) having a
high energy or fitness cost, so that the trait can act as an indicator of overall fitness; 3) high
sexual differentiation, since usually a sexually selected trait is used by one sex as a way of
deciding between the members of the other sex; 4) having a high degree of variance, allowing
the trait to be used as a means of distinguishing between members of a sex; and 5) having a high
degree of heritability, so that the possessor reliably passes on the trait to its offspring. Where
one can determine that a trait has these characteristics, one has reason to think that the trait in
question was produced by sexual selection. Miller’s argument is, in essence, that art and altruism
in humans possess just these characteristics – therefore they are likely to be sexual adaptations.
In that case there are clearly two main ways to criticize Miller’s argument. First, we can
attack his claim that “art” and “altruism” really do possess his five characteristics. Second, we
can show that there is another process that is equally likely to produce those five characteristics
in human behavioral traits. In Sections 5 and 7 I will follow these two lines of attack in turn.
First however, we need to decide what kind of traits Miller has in mind when he uses the terms
“art’ and “altruism”.
4. What are “Art” and “Altruism”?
One of Miller’s difficulties in his book is that he is not clear about what exactly his
hypothesis is – in particular, what kind of adaptations he has in mind by “art” and “altruism”.
Miller on Art, Altruism and Sexual Selection 11
The sexual adaptations for art and altruism could be some kind of psychological mechanisms that
produce art and altruism; they could be artistic or altruistic behavior; or they could be the
products of altruistic and artistic behaviors – altruistic gifts and works of art. Whatever it is
Miller does have in mind – behavior, artifact or mechanism – it has to be the kind of thing that
can actually possess the five identifying characteristics of sexual adaptations.
Consider first what Miller might mean by “art”. In the production of art, on his view,
something like the following occurs. First of all, humans possess a suite of sensory-motor
capacities, which are involved in both the production of art and in other kinds of behavior. Miller
claims that high quality sensory motor skills are likely to be well correlated with fitness and
clearly intends these skills to be the fit properties that the artistic sexual adaptation must indicate
(p.281). On Miller’s view humans also possess some sort of psychological mechanism(s) that
give them the desire and motivation to produce art. The interaction of this psychological
mechanism with the sensory motor capacities produces artistic behavior. The consequence of
artistic behavior is sometimes an independent artwork; sometimes the behavior itself counts as
the artwork (e.g. singing, dancing, acting). So is the artistic adaptation the mechanism, the
behavior or the artwork?
If Miller has in mind the psychological mechanisms for art, then he has a problem, since
it is clear that psychological mechanisms per se cannot be used by potential sexual partners as
fitness indicators, since they do not vary as a function of the quality of the sensory motor skills
that are supposed to be correlates of fitness. Instead, the psychological mechanism interacts with
those sensory-motor skills to produce artistic behavior or artworks – which do vary in the
appropriate way. This leaves us artistic behavior and the artworks themselves as the only
possible candidates for sexual adaptations. A similar problem arises in the case of altruism –
Miller on Art, Altruism and Sexual Selection 12
Miller is not clear whether he is trying to identify a psychological mechanism for altruism,
altruistic behavior, or the altruistic gifts themselves. Nor is it clear exactly what beneficial trait or
traits Miller thinks are indicated by the altruistic sexual adaptation. One possibility Miller might
have in mind is that altruism, some of the time, is the consequence of the interaction of
psychological mechanisms for altruism together with, in some cases, practical resources – e.g.
money, food, etc. - to produce certain sorts of behavior. Since the type and extent of altruistic
behavior produced by the mechanism, and the absolute gifts themselves depend on the available
resources, altruistic behavior and altruistic gifts will both vary as resources vary. If this is what
Miller means, then the fitness property for which altruism is a fitness indicator is really the
possession of those resources. Just as in the case of art, a psychological mechanism for altruism
is not what is indicating the presence of those resources because it doesn’t vary as a function of
those resources. Rather, it is the altruistic behavior or gifts that indicate fitness. Hence if the
altruistic sexual adaptation is to indicate fitness, then it must either be altruistic behavior, or it
must be the altruistic gifts themselves.
Consequently, Miller’s choices for his artistic and altruistic sexual adaptations are either
artistic and altruistic behaviors or artworks and altruistic gifts per se. Miller occasionally
suggests that the latter is what he has in mind (Miller, 2000, p.270-1). However, the idea that
artworks or gifts are in themselves traits of human beings and, what is more, sexual adaptations,
is somewhat strange. The alternative is for Miller to accept that artistic and altruistic behavior is
itself a sexual adaptation. This looks like the most plausible of the possible hypotheses available
to Miller. However, Miller identifies as an evolutionary psychologist, and as such might want to
resist the idea that behavior is the appropriate level of description at which to direct evolutionary
explanations, as have others in his field (e.g. Cosmides and Tooby, 1987). I think this would be
Miller on Art, Altruism and Sexual Selection 13
a mistake. Either way, Miller needs to be clearer about what exactly his hypothesis is.
5. Do art and altruism have the five characteristics?
In order for Miller to make his argument he must offer reasonable evidence that art and
altruism do in fact possess his five characteristics. In the sections that follow I am going to argue
that there are serious problems with this claim. In particular, I am going to argue that Miller’s
case is much weaker for altruism than it is for art, and hence an explanation for altruism in terms
of some other kind of process might be justified.
5.1. Lack of evidence of courtship involvement in art and altruism
It is arguable that of the five characteristics Miller identifies, the involvement in courtship
is the most clearly indicative of the activity of sexual selection. If art and “showy” altruism are
sexual adaptations, it must be the case that being a good artist or altruist is likely to allow you to
attract more or better sexual partners than those who are not good artists or altruists. This is, I
think, the most difficult part of Miller's case; at least partly because when studying humans it is
difficult to show that possessing some trait increases a person's sexual success.
Miller's main evidence that art is implicated in courtship comes from the natural world;
that the closest thing to "artistic" behavior in animals does seem to have a courtship function. His
example is the nest building behavior of male bowerbirds. Male bowerbirds build bowers that
have no function beyond attracting the attention of females; females mate with males who build
the bowers they like the best, and they appear to make these choices on purely aesthetic grounds
(Miller, 2000, p.267-70). However, although it might be clear that the "artistic" behavior of
bowerbirds has a function in courtship, it is not so clear this is true in humans. Part of the
Miller on Art, Altruism and Sexual Selection 14
problem is the sheer difficulty of demonstrating a connection between (good) artistic behavior
and sexual success - how would one go about demonstrating that good artists on average do
better sexually than bad, or those who are not artistic at all? At best there is anecdotal evidence
that individuals find talented artists attractive, and Miller does facetiously refer to the notorious
sexual success of Picasso, Gauguin and Modigliani (p.274).
Miller does argue that the courtship requirement is not a very challenging criterion; that
"it was not necessary for hominids to favor great artists over great hunters or great
mothers…only for them to favor those who showed taste and talent in their everyday self
ornamentation over those who did not, all else being equal" (p.274.) However, body
ornamentation is very different from, say, painting or sculpture – if we had evidence that body
ornamentation was employed in courtship, this would not be clear evidence that the same was or
is true of paintings and sculptures. Nevertheless Miller purports to explain the latter as well as
the former via sexual selection. Clearly Miller needs to address this problem more carefully.
Just as in the case of art, Miller cites examples from the natural world where altruism is
used as a form of courtship display; one example he uses is Amotz and Avishag Zahavi's (1997)
study of Arabian babblers. These birds live in large groups in which a few of them behave in
ways that are conspicuously altruistic. They share food with non-relatives and help with
unrelated offspring; they act as sentinels - give alarm calls to warn of approaching predators and
mob the predators if they come too close. Since the birds help non-kin, and actually compete
rather than avoid the sentinel job, this does not seem to be a case of either reciprocal altruism or
kin selection. What is more, only birds that are very fit and in good condition are able to take
over this role - Zahavi believes that the altruism is a form of sexual display employing the
handicap principle. Is altruism amongst humans the same?
Miller on Art, Altruism and Sexual Selection 15
Miller uses evidence regarding the hunting behavior of men in foraging societies to claim
that altruism may be used in courtship in humans (Miller, 2000, p.308-14). In these societies men
usually spend their days hunting. Their behavior seems odd for several reasons. First, men
usually spend most of their time going after really big game that are hard to catch and unreliable
sources of food. Second, men using this method have a (sometimes much less than) 10% chance
of bringing home food each day. Third, when men are successful and bring something home,
they tend to share the food with the whole tribe. The reason for this behavior might be some sort
of reciprocal exchange of food, since if everyone eats whenever a man catches something,
everyone eats some meat more often and the meat supply is more stable. In practice this is not
how it works, since reciprocity depends on men being equally good hunters; for reciprocity to
work, one person has to be able to pay the other back as much as was given, but where hunting
ability varies considerably this cannot be the case. A poor hunter cannot reciprocate properly
with a good hunter. And in fact, men do vary in their hunting ability (see Kristen Hawke’s
(1993) discussion of the hunting practices of men in hunter-gatherer societies). Miller claims that
these successful hunters are in fact making a sexual display; they feed everyone in a costly way
and they are able to have more or better sexual partners as a consequence. Miller argues that this
pattern of sexual display may have evolved partly by group selection, since groups with this
practice do better than groups with other sexual selection practices. The problem with this
example is that although altruistic sharing is involved in this case, it seems that altruism is
indicating hunting ability– and hence it is not clear whether this is evidence of how extreme
altruism might have evolved in cases where altruism has to indicate something other than
hunting.
Miller also cites David Buss's (1990) study of sex preferences across 37 cultures, where
Miller on Art, Altruism and Sexual Selection 16
"kindness" was the single most important feature desired in a sex partner by both men and
women in every culture; more important than beauty, intelligence and status. Miller takes this as
evidence that altruism is a trait that is sexually desirable across cultures (Miller, 2000 p.292). If
individuals really do look for altruism when choosing a partner, then there may be some reason
to think that individuals might want to flaunt altruism during courtship. While this may be good
evidence that kindness is a trait that is used in courtship display, it is not clear that the “kindness”
referred to on Buss’s study is “altruism” in the biological sense – engaging in behavior that
involves taking on a fitness cost for others. Nor is it obviously the extreme, showy altruism that
Miller wants to explain.
5.2. Does artistic behavior act as a fitness indicator?
As well as having problems with how art fits the courtship involvement criterion for
being a sexual adaptation, Miller also needs to account for the serious problem about how far
real artistic behavior acts as a fitness indicator. As I explained in Section 4, the most obvious
way to understand Miller’s hypothesis that art is a sexual adaptation is to take artistic behavior or
artworks to be fitness indicators for underlying sensory-motor capacities. Miller thinks the
fitness indication of artistic behavior is to be found in the nature of the psychological, perceptual
and physiological capacities necessary to produce good artistic behavior. He argues that human
aesthetic preferences find most beautiful those things that are most demanding on the producer that require large quantities of "health, endurance, hand-eye co-ordination, fine motor control,
intelligence, creativity, access to rare materials, the ability to learn difficult skills and lots of free
time (p.281). He goes on to argue that there is evidence that creativity is well correlated with
intelligence; and that it may have other kinds of fitness value (p.409).
Miller on Art, Altruism and Sexual Selection 17
This is all very well – clearly artistic behavior could act as an indicator trait. However,
Miller now has a new problem. Quite a lot of real artistic behavior, especially within the modern
avant-garde, is not meant to be a show of beauty and/or technical skill (except perhaps
intelligence and creativity). In fact, the point of certain forms of art (for example, DaDaism) is to
flout human beings’ conceptions of what aesthetically pleasing things ought to be like. If so, how
can this kind of artistic behavior are accounted for as a sexually selected indicator trait? Miller
tries to get around this problem by making a distinction between the kinds of art he is trying to
explain (simpler early forms of ornamentation, representation, singing, etc,) and the art produced
as a consequence of modern cultural institutions. Miller claims that the rise of conceptual and
avant-garde art is permitted by the presence of cultural institutions for art that permit forms of
artistic production and behaviors that are not entirely connected to the original adaptations for
producing and judging works of art. Being part of an artistic institution now confers status,
especially on insiders who "understand" new forms of art (p.284-5). I take it that Miller means
that artistic behavior produced by many of those participating in these institutions is a cultural
rather than a biological phenomenon, though one that borrows from human beings’ biological
heritage; nevertheless it is pursued out of a (biological) desire for high status.
Miller claims that this shift away from the original function of artistic behavior as an
indicator of fitness is evidenced by the responses of "ordinary folk" to the works of the artistic
avant-garde. Their confusion reveals that they are looking for a display of skill on the part of the
artist (p.284-5). Miller also thinks that the modern desire for handmade imperfection in objects
rather than mass-produced perfection is evidence of the fact that human beings are looking for
works that really express human skill (p.286-8). This explanation, however, does weaken his
argument since it is a concession that not all art can be explained by the sexual selection
Miller on Art, Altruism and Sexual Selection 18
hypothesis.
5.3. The reality of sexual differentiation in art
Another area where Miller has serious trouble making his case is in regard to the sexual
differentiation in the traits he is studying, particularly in the case of art. Do only men have sexual
adaptations to produce artistic behavior, or at least stronger adaptations to produce artistic
behavior than women do? Up to the present century, with its new freedoms for women - but also
its development of new and complex artistic institutions - men were the main producers of art4.
This might mean that artistic behavior is purely a sexual adaptation in men, and that artistic
behavior in women is either a side effect, or the result of cultural changes that encouraged
women to involve themselves in artistic institutions; i.e. artistic behavior in women is a cultural
rather than a "biological" phenomenon. Or the higher production of art by men might be due to
the cultural oppression of women.
There are three possible ways for Miller to respond to this piece of evidence without
undermining his argument. The first is to accept the sex differentiation, and claim this as
evidence that artistic behavior really is a sexual adaptation - for men. Miller, understandably,
wants to resist this conclusion, and to argue that women's capacity for artistic behavior is real,
whilst still maintaining that artistic behavior is a true sexual adaptation. This is not just because
Miller wants impeccable feminist credentials, but also because women do make art now and at
least some of the time in the past. It would be very surprising if a costly indicator trait were
4
Of course, this observation may simply be due to a tendency to focus on the forms of art (such as painting,
sculpture, classical music, etc.) that were primarily produced by men, rather than the forms of painting and
(particularly household) ornamentation produced by women.
Miller on Art, Altruism and Sexual Selection 19
maintained in a sex that didn't need it to indicate sexual fitness; if women don't need artistic
behavior, it ought to be selected against in women. If artistic behavior continues in women
despite its costs, it might suggest that the origin of artistic behavior was as something other than
a standard sexual adaptation.
This leaves Miller with two possible avenues for argument. First, he can argue that
humans are a largely monogamous species, and this meant that in human history males often
exercised sexual choice in monogamous relationships, and that they preferred artistically talented
women to those women who were not (p.383-6). Hence artistic behavior is a sexual adaptation in
women, as it is in men; male predominance in the arts is just a symptom of a patriarchal culture.
Second, Miller could argue that artistic behavior as a sexual adaptation requires a two way
relationship: producer and consumer (p.375-7). The idea, of course, is that men are the producers
of artistic behavior and women are the consumers. If artistic behavior is to work well as an
indicator trait, then the consumers of art have to be very good at distinguishing good art from
bad; and this will probably require that the consumer have as fine skills of judgment and
intelligence as the producer. Miller claims that the producer-critic distinction predicts that men
(producers) will make more art; and that women (consumers), when they and were they to make
art, would be as good at it as men are.
I don't agree that Miller’s distinction really predicts this. Miller is right that the consumer
producer distinction predicts that consumers and producers must share some of the same
capacities in common – indeed it seems that visual artists, for example, rely on the similarities
between their own perceptual mechanisms and that of their audience to make their point
(Cavanagh, 2005). However, creating art requires the individual to have, among other things,
fine motor skills and creativity, not just certain perceptual abilities; and if being selected for
Miller on Art, Altruism and Sexual Selection 20
being a consumer is to give women the skills to be producers, then being a consumer will have to
require exactly the same abilities as being a producer. It does seem strange to suggest that you
need fine motor skills and creativity to appreciate art. One possible way Miller could turn out to
be right is if appreciating art requires a kind of mental simulation of the task of generating it, so
that motor mechanisms that would be used in production were used “offline” in consumption.
Neuro-imaging could show whether the same systems become active in both production and
appreciation of art. However, Miller does not provide any evidence of this kind.
5.4. Can altruistic behavior act as a fitness indicator?
I think that there is much more serious objection to Miller’s claim that altruism meets his
second criterion, that of being costly in order to act as an indicator of genetic fitness. Not only
does Miller have very little evidence that altruism acts as an indicator trait, he is very unclear
about how altruism acts as an indicator. Miller argues that if showy, extravagant altruism (or
indeed, any kind of altruism) is to act as a fitness indicator, it should not only be costly, but
individuals should take on the cost as publicly as possible, so that potential mates can take note
of it. Obviously, altruism by definition involves taking on a fitness cost to oneself in order to
benefit others; the question is whether taking on this cost is a way of indicating that one is fit or
otherwise in possession of extensive physical and/or genetic resources. Miller argues that in fact,
individuals acting altruistically are more interested in the cost of an altruistic act than they are in
its positive consequences; just as they should be if they were interested in making a display
rather than engaging in a nepotistic or reciprocally altruistic interaction. He uses as his examples
the lack of interest that individuals show in the efficiency of the charities to which they
contribute (p.324). Miller also thinks that wealthy individuals who work in soup kitchens instead
Miller on Art, Altruism and Sexual Selection 21
of giving money are trying to make a successful display; just as are male hunters who go after
big, inefficient prey rather than smaller, easier to catch prey.
One possible explanation for the origin of altruism that Miller suggests is via a
combination of sexual and group selection, as in the case of altruistic sharing amongst hunters
that I described earlier. Hunters who share their food are making a sexual display; and as such
the behavior can evolve by sexual selection. Because this form of sexual display is also group
beneficial, groups with this behavior out-competed groups without it. In the hunting case,
altruistic displays indicate hunting ability and the associated skills. However, many altruistic
gestures are not so obviously cases where skills are being displayed. What can we say about
these cases? Since the most obvious cost of altruistic gifts is their dollar cost, one possibility is
that altruistic gestures are supposed to demonstrate the extent of the resources of the altruist. On
this view, altruism is a form of conspicuous waste to show how much money or other resources a
person has available; just as the peacock's tail is a conspicuous waste of the bird's developmental
energy, thus displaying how much energy there is available. Those who are poor or sickly cannot
make such large displays, and therefore they are sexually selected against by members of the
opposite sex. If this “dollar value” view of altruism as a sexual indicator is what Miller has in
mind, then there is at least one serious problem with his view – how do we account for
individuals’ tendency to praise altruistic acts - including extreme altruistic acts - that are not
directed at them? On other theories of the origins of altruism, praise is a reward for altruism,
since praise improves one’s reputation and social standing – it provides some individual benefit
that allows altruism to evolve. However, on Miller’s view there is no need for rewards for
altruistic behavior to allow it to evolve, since altruism should be individually useful, due to its
tendency to increase its possessor’s sexual success. Miller does suggest that moral approbation
Miller on Art, Altruism and Sexual Selection 22
on the part of potential sexual partners is (at least partly) a manifestation of sexual interest.
However, it is unlikely, given the way that altruistic praise operates, that both this view of the
nature of moral praise and the “dollar value” view of altruism can both be true. If altruism is to
act as an indicator of overall wealth, and more importantly, an indicator that can't be faked by
poorer individuals, then altruistic gestures need to be made as a direct proportion of one's
wealth5. So wealthy individuals should give proportionately more than poor individuals, and
large gifts should be proportionately more attractive than small ones. If moral approbation on the
part of potential sexual partners is a reflection of the degree sexual interest, then big gifts should
receive proportionately more praise than small gifts, ceteris paribus. However, it is not clear that
the bigger in dollar terms the act of altruism, the more people praise it – something else seems to
affect the degree of approbation proffered. For example, people do not seem to be more
impressed by a millionaire that gives $110 to charity than a poor person that gives $100.
Nevertheless if art is a straightforward indicator of wealth, the applause for and thus sexual
interest in altruism must be directed at the behavior that shows the highest cost. Another problem
with the idea that altruism acts as a form of "dollar value" fitness indication is that there are
easier ways for a person to find out what a person's wealth and status are than via their altruistic
5
There are three ways that gift size can increase as wealth size. 1) Gift size can be proportional to wealth size; 2)
gift size can increase as a percentage of wealth size as wealth size increases, or 3) gift size can decrease as a
percentage of wealth as wealth increases. Suppose relation 3) is the standard way of indicating wealth. Then for each
dollar a person P gives, it appears that P is disproportionately more wealthy (e.g. suppose you give one dollar for
each of the five first $1000 you own, then one for each of the next five $10000 dollars, etc.) Therefore, since the
wealthier P appears, the more sexual opportunities P gets, it would be worth P’s while to give more dollars than
properly indicates his wealth – to fake – since the fitness costs of paying more dollars will be outweighed by the
fitness benefits of disproportionately more sexual opportunities.
Miller on Art, Altruism and Sexual Selection 23
giving, which may or may not be well correlated with their total net worth. If these more reliable
means of fitness indication are available, why waste time paying attention to altruism?
An alternative way in which the costliness of altruism might act as a fitness indicator is if
by choosing altruists, women are choosing good fathers. This form of sexual choice might work
because altruists are generous - willing to help others, and hence probably their own children
(p.334). However, there is a problem with this idea, too. The best fathers are nepotists, not
altruists, since nepotists and altruists are both nice to their children, but altruists are a little bit too
willing to give away the family wealth to charity. Miller thinks that maybe altruists do better
with stepchildren (an inevitable part of the Pleistocene family) than nepotists. Possibly, but why
should women choose altruists for this reason, when they can just directly choose men who are
good with their children? Indicators are used to tell us about something we cannot directly
observe in the individual we are judging.
So Miller has not established how altruism is supposed to work as a fitness indicator,
even if it is clearly costly. His case that altruism is a sexual adaptation is consequently
considerably weaker than his case for art – after all, it seems clear how art could act in courtship
and as a fitness indicator, even if Miller’s evidence that it does is not very strong. In the next
two sections I will consider the serious alternatives to Miller’s claim that art and altruism are
sexual adaptations. Altruism, which does not seem likely to possess Miller’s five characteristics,
can be better explained in terms of genetic or cultural group selection. In the final section I
suggest an alternative process, cultural sexual selection, which can produce traits with most of
Miller’s five characteristics; this might account for art if art does indeed turn out to possess those
characteristics.
Miller on Art, Altruism and Sexual Selection 24
6. An alternative explanation for altruism
Given that altruism does not look like a sexual adaptation, it seems to be appropriate to
look for an alternative explanation. The best explanations for altruistic behavior in the literature
usually invoke some form of group selection (for a discussion, see Sober and Wilson, 1998).
Group selection is a process by which groups or organisms are selected for based on their group
level properties. Group level properties are different from individual level properties – for
example, an individual level property would be “being selfish” or “being altruistic”; on the other
hand a group level property would be “composed largely of altruists.” During group selection,
groups give rise to different numbers of new groups due to their group level properties. We can
then explain the prevalence of altruism in a population by appealing to the affect on group
reproduction of having many altruists in groups – altruists contribute to the fitness of everyone in
their group and hence altruist-dominant groups tend to do better than groups that are mostly
composed of non-altruists, all else being equal. This means that while altruists may decrease as a
proportion of any group in each generation (since there is individual level selection against
altruists because of the fitness costs they pay to others), altruistic groups contribute more
members to the population as a whole, and the number of altruists in the total population tends to
increase.
Group selection explanations for altruism do face problems, however. The first problem
is that group selection only occurs when there are stable, significant differences in the group
level properties of those groups. This requires that group selection (for altruism in particular) can
only occur in cases in which there is assortative group formation – that is, group selection for
altruism can only occur where altruists tend to group together, as do non-altruists. A second
problem is migration of individuals between groups – which happens in every population.
Miller on Art, Altruism and Sexual Selection 25
Migration, because it is random, tends to reduce differences between groups. A third problem is
how to get group selection for altruism going, given that altruism tends to reduce the individual
level fitness of individuals. In order to get groups with large numbers of altruists, there have to
be reasonable numbers of altruists in the population to begin with. However, altruists are selected
against by individual level selection when they arise. The fourth problem for group selection is
how to deal with the relative pressure of individual level selection verses group selection –
unless groups periodically break up and re-form, altruists will eventually die out as members of
any group. Ideally, there should be some way in which altruists can be helped to maintain
greater fitness parity at the individual level with non-altruists.
The following proposals have been made in the literature for dealing with these problems.
For humans, Sober and Wilson (1998) argue that the first problem (assortative group formation)
would not have been that much of a problem. In the earlier part of human history we belonged to
small, flexible social groupings that allowed us to observe and talk about the behavior of others
and thus make decisions about those with whom we wanted to associate (Sober and Wilson,
1998. p.141-2). The second problem (migration) can be avoided if altruism has a primarily
cultural origin – it is a trait that is socially learnt. This means that individuals coming into
altruistic groups need not remain non-altruistic – they can change their behavior appropriately;
alternatively their children can come to acquire altruism, and hence, over generations, migration
will not cause changes in the proportion of altruists in groups. The acquisition of altruism can be
made more reliable via a conformist bias in learning (a conformist bias is a learning heuristic that
leads the individual to acquire the cultural trait that is most prevalent in the group they are
entering - Henrich and Boyd, 1998) or via the use of punishment (see the next paragraph for an
explanation for how punishment works).
Miller on Art, Altruism and Sexual Selection 26
The solution proposed to the third and fourth problems is that altruistic behavior can
become prevalent, and group selection become stronger than individual selection in altruistic
groups, if there is some way of creating greater parity in the individual-level fitness of altruists
and non-altruists (Sober and Wilson, 1998, p.142f). There are two ways to do this – either
increase the individual-level fitness of altruists, or decrease the individual-level fitness of nonaltruists (or both). This means imposing punishment on non-altruists, or offering rewards to
altruists. Punishments do require some payment of cost on the part of the punisher, making
punishment itself an altruistic behavior - Sober and Wilson call it secondary altruism. If the costs
of punishing are low, the benefit of keeping other members of the group in line might outweigh
the costs to the punisher; therefore punishing behavior might also evolve by group selection.
(The same is true for rewards).
The previous discussion suggests cultural group selection of altruism is a least possible.
How might this explanation for altruism account for the extreme or showy altruistic acts Miller is
trying to explain? We’ve already seen that one of the important requirements for the occurrence
of group selection for altruism is the presence of punishment or rewards for certain types of
behavior. Groups can maintain altruistic behavior by punishing selfishness or by rewarding
altruism. But this creates an interesting situation – what is important to the individual is receiving
the reward/avoiding the punishment, not offering the group benefit. In order to get her reward
from the rest of a group, it is in an individual’s fitness interests to be focused on making sure
everyone (or at least those responsible for rewards and punishments) is aware of her
contribution, even at the expense of the actual value of that contribution to the individuals she is
helping. Hence individual selection favors “showy” altruism to maximize potential rewards and
minimize punishment – whilst still offering some group selective benefit in the form of some
Miller on Art, Altruism and Sexual Selection 27
help to other members. Therefore it might be possible for forms of altruism that are not as
straightforwardly beneficial to the group to be maintained by a combination of individual
selection and cultural group selection.
So what empirical evidence might count in favor of this sort of explanation of “showy”
altruism over Miller’s sexual selection hypothesis? The first component of my hypothesis is that
altruism evolves by cultural group selection. One piece of evidence that would support this is a
demonstration that cultural group selection can occur at the rate necessary to fix altruism. Such a
demonstration already exists - Soltis, Boyd and Richerson (1995) have shown that cultural group
selection is possible in the long term (it would take on the order of 500-1000 years for the spread
of a group beneficial trait). Another piece of evidence necessary to show that the cultural group
selection story for altruism is true is whether altruism could evolve by cultural group selection
under reasonable assumptions about the conditions under which historical groups existed and
given reasonable time scales – this could be established via mathematical modeling. Finally,
there would also have to be evidence that there is (culturally based) variation in altruism between
societies. Some ethnographic research performed by Joseph Henrich et al (Henrich et al. 2004)
does suggest that there is inter-social variation in altruistic and cooperative behavior, and these
variations appear to co-vary with environmental and social factors that increase or decrease the
social utility of altruism.
There is also some, more limited evidence for the second component of my hypothesis,
that altruism is maintained by punishments and rewards. One piece of evidence is the relative
prevalence of punishment in groups that show higher levels of altruistic sharing and cooperation
than others. One of the experiments used to examine people’s economic interactions is called the
“ultimatum game” – in this task, one person, A, is given a sum of money to divide between
Miller on Art, Altruism and Sexual Selection 28
themselves and another individual, B. A can make any offer they like to B - if B accepts the
offer, they each keep the amount that A has suggested. If B rejects the offer, neither of them gets
anything. If people were ideal rational individuals, then B would accept any offer that A made –
something being better than nothing. However, even in situations where a lot of money, B
individuals in western cultures will not accept offers that are fairly low; and indeed, A
individuals in the west tend not to make low offers. One explanation of this is that B individuals
reject offers out of spite, or a desire to punish A individuals for not being fair, even at cost to
themselves. Henrich et al.’s (2004) work suggests that ultimatum game interactions with high
levels of spite and “punishment” occur in societies where altruistic and cooperative behavior is
more important for survival and vice versa. This does provide prima facie evidence that
punishment has a role to play in maintaining altruism (although it does not show that rewards are
equally important).
It is the third component, however, that is crucial to my hypothesis – that punishment and
rewards provoke altruistic grand gestures as a way for individuals to secure rewards or avoid the
punishments. The following evidence would count in its favor. First, if grand altruistic gestures
are a way to secure benefits from others, they should be most common in cases where the person
is likely to be observed by many individuals, or where relevant individuals (who decide on
rewards and punishments) will see them. Second, variations in the rate of occurrence or size of
altruistic gestures should vary with the size and importance of the rewards and punishments
present in a society. In societies with more or more costly punishment or higher rewards, the
importance of being seen to be altruistic (rather than just being altruistic) becomes more
important (for fitness at the individual level), and individuals should make more altruistic
gestures to compensate. Finally, it suggests that it is more important to individuals to be seen to
Miller on Art, Altruism and Sexual Selection 29
be altruistic than to be actually altruistic and will adjust their behavior accordingly. There is
some evidence that this is the case – Kagel et al. (1996) have shown that where ultimatum game
proposers in western societies have information that their offer is worth less than the recipient
thinks it is, they will reliably make apparently fair offers to the recipient, rather than the actual
fair offer.
7. Cultural sexual selection can account for the five characteristics
Having described an alternative process by which altruism could have arisen in human
beings, I am now going to describe an alternative process which can account for traits with
Miller’s five characteristics. Miller’s argument relies on the idea that traits with the five
characteristics are much more likely to be produced by sexual selection than by any other
evolutionary process. However, there is a form of cultural selection (for a discussion see Boyd
and Richerson 1985) that can consistently produce the same characteristics as standard sexual
selection: what I call cultural sexual selection. Suppose there is a behavior B, which is socially
learned within families - i.e., if a parent of one sex possesses B, then the offspring of the same
sex are very likely to learn B from that parent. Now suppose that B makes its possessors more
attractive to the opposite sex, such that possessors of B have more partners and more children, or
better partners and thus children who are more likely to survive, than those which do not possess
B. Then B could spread through the population. Cultural sexual selection for B, however, just
like standard sexual selection, relies on there being mate preferences for B in the population. Just
as with standard sexually selected traits, these preferences can become subject to natural
selection - individuals who have poor mate preferences will produce fewer offspring. Where
mate preferences are reliably transmitted from parent to child (either via genes or by social
Miller on Art, Altruism and Sexual Selection 30
learning) poor preferences will be out reproduced by good preferences. Hence cultural traits that
are fitness indicators –and therefore possess all or most of the five characteristics - will be
culturally sexually selected for. Preferences for such culturally sexually selected traits and the
traits themselves would both be transmitted in families and therefore could be subject to runaway
cultural sexual selection.
In other words, cultural sexual selection could account for most of the five characteristics
that sexually selected traits possess: i.e. involvement in courtship, fitness-indicating cost,
variability and sexual differentiation. What evidence might count in favor of this hypothesis,
over Miller’s? Evidence for the five characteristics in a trait could support either a standard or
cultural selection explanation for that trait. The essential difference between the two processes is
the transmission mechanism they require – for Miller, the transmission mechanism is, ultimately,
genes; in the cultural sexual selection hypothesis the transmission mechanism is social learning
in families. In support of his standard sexual selection mechanism, Miller might try and show, for
example, that traits with the five characteristics are cross culturally heritable (in the technical
sense that variation in those traits is accounted for primarily by variation in genes).
Demonstrating cross cultural heritability is necessary to support Miller’s hypothesis, since traits
that are obviously socially learnt can be highly heritable within cultures (for example, political
persuasion). The reason is that the main thing that varies between individuals who acquire
different traits in the same cultural environment is the psychological mechanisms those
individuals possess, and variation in those psychological mechanisms is accounted for largely in
terms of variation in genes. However, the explanation of the variation in traits such as political
persuasion between cultural environments is likely to be much more dependent on variation in
the cultural environment than on variation in psychological mechanisms and thus variation in
Miller on Art, Altruism and Sexual Selection 31
genes. Where the main variant in the difference between traits across cultures was genes, that
would strongly support Miller’s view; if those traits varied more strongly with cultural
environment, that would tend to support the cultural sexual selection view. However, the cultural
sexual selection hypothesis is more than the view that the cultural environment is important to
the generation of traits; it is the view that it is social learning within families that is the
transmission mechanism. So supporting this view would also require some form of ethnographic
evidence for the kinds of learning practices and patterns associated with the traits in question
suggesting that it was social learning in families itself that transmitted the trait and not some
other kind of social learning, individual learning or some other kind of environmental influence.
So could the cultural sexual selection story explain the character of art? I think it is a
plausible hypothesis, but one that would, obviously, have to be supported with some of the
evidence described above. One obvious objection to this hypothesis is that art does not
apparently possess the five characteristics, (which are just as much required evidence in favor of
a cultural sexual selection hypothesis as they are on a standard sexual selection hypothesis).
However, I think that the ways in which art deviates from the five characteristics can be more
naturally explained by a cultural sexual selection story than by Miller’s view. One such problem
is the presence of a sex bias in art. Artistic-type behaviors are often taught by one person to
another, either by copying or via complex learning institutions and apprenticeships. Sex bias in
art might also be more easily explained by certain kinds of cultural transmission – where artistic
behaviors of a certain sort are only culturally transmitted to men, regardless of how interested
women are in acquiring them, or how capable women would be in performing them. Again,
shifts in the kinds of cultural transmission for art could also explain the relationships between the
initial rise of art and art produced in present institutions more naturally than Miller’s suggestion.
Miller on Art, Altruism and Sexual Selection 32
Cultural artistic behavior could originally have been spread parent to child, and hence have
become sexually adaptive, however, it could also eventually be passed on by other forms of
social learning. Artistic behavior passed on by social institutions would not have to retain the
sexually adaptive characteristics that originally made it common, since those would no longer be
the properties that were maintaining it in the population.
8. Conclusion
Miller’s work does an important job in at least one regard – it is a good reminder that
sexual selection as understood by Darwin (1874) may be an important tool in understanding
certain aspects of human and animal behavior. However, it is not clear that Miller has a very
good case to make that the behaviors he focuses on are in fact sexual adaptations. The first
problem is that the evidence that art and altruism possess the characteristics unique to sexual
adaptations. While Miller has a problem making his case for both traits, the problems are more
pronounced in the case of altruism.
Miller’s other problem is the presence of other, highly plausible alternative explanations
for altruism and other traits that possess the five characteristics. Altruism, even of the highly
showy and extravagant kind that Miller has in mind, seems to be naturally explained by a
cultural group selection view employing punishment as a means of promoting the individual
level fitness of altruists vs. non-altruists. Showy altruism is a way of making sure that one’s
altruistic contribution is seen and receives its appropriate reward or avoids a punishment. There
is already some empirical evidence that suggest important elements of this hypothesis are true.
Another cultural transmission view, cultural sexual selection, might account for the presence of
traits with the five characteristics, and might do a better job explaining why art in particular
Miller on Art, Altruism and Sexual Selection 33
deviates from the five characteristics that mark sexual adaptations.
Miller on Art, Altruism and Sexual Selection 34
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