Could sexual selection have made us psychological altruists?

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Abstract

Psychological altruism (being motivated by the needs of others) has a tendency to produce behaviour that is costly in evolutionary terms. How, then, could the capacity for psychological altruism evolve? One suggestion is that it is the result of sexual selection. There are, however, two problems that face such an account: first, it is not clear that the resulting behaviour would be altruistic in the relevant sense, and second, it does not seem to fit with key features of our actual helping behaviour. I will argue that both of these problems can be avoided if we adopt a modular account of desire formation.

Introduction

As Gregory Kavka has pointed out, being motivated by the interests of others has a systematic tendency to produce behaviour that helps those in need, behaviour that tends to be costly for the actor (see Kavka, 1986, p. 61). When those who have the capacity to be motivated in this way come across someone in danger, they will have some motivation to rescue them; and when they come across those who are starving they will have some motivation to feed them. Of course, they may not always act on that motivation. But, on those occasions when they do, they decrease, by however small an amount, their own chances of survival. Sharing resources with those who lack them, for example, means that these resources are not available should they be needed later—a particular problem where resources are scarce or are likely to become so. Those who lack the capacity to be motivated by the interests of others will not take these risks to the same extent (although that is not to say that they will not take them where they see some personal benefit in doing so). In each generation, therefore, those with this capacity will be more likely to help others in a way that damages their own chances of survival than those who lack it. As a result the proportion of the population with the capacity to be motivated by the interests of others will go down over time. Given enough time it will be removed from the population entirely.

If this story is correct, then it would provide strong support for those who hold that we are not capable of being motivated by the interests of others.1 But is it correct? A first step in challenging it may be to note that the helping behaviour it describes is not only altruistic in the sense that it is motivated by the interests of the individual being helped (which I will call ‘psychological altruism’), but also in a more technical sense (which I will call ‘evolutionary altruism).2 Within evolutionary biology an act is described as altruistic if it has the effect of decreasing the actor’s fitness while increasing the fitness of others (see Wilson & Dugatkin, 1992, pp. 29–33). Going to rescue someone in danger, or sharing your resources with those in need, both seem to be altruistic in this more technical sense. In this they are not alone. Behaviour that appears to be altruistic in the evolutionary sense is widespread in the natural world. Biologists have taken a variety of strategies when trying to account for it. They have, for example, variously argued: 1) that far from reducing your chances of surviving, helping may actually increase them (this is the strategy taken by advocates of both reciprocal altruism3 and group selection4 accounts); 2) that while helping may reduce the helper’s chances of surviving, it may at the same time increase the chances that their close relatives will survive, and so spread in this way (the approach taken by advocates of kin selection accounts5); 3) that helping may have been selected for precisely because it is costly (the line taken by sexual selection theorists). Each of these approaches has had some success in accounting for evolutionary altruism in non-humans. This raises the possibility that one or more of them could account for psychological altruism as well.

What I want to do here is to focus entirely on the third option: sexual selection. I will argue that it can account for the human capacity for psychological altruism, but to do so it will need to make use of a particular idea about how the mind is structured. It is important to note here that parts of this argument will be highly speculative. As such, I am not claiming to have shown that psychological altruism in humans exists and was produced by sexual selection. Rather, my aim is more limited, being simply to show that our capacity for psychological altruism could have been produced by sexual selection.

Section snippets

Sexual selection

Rather than focusing on survival, sexual selection accounts start from the idea that, for sexually reproducing species, the number and quality of mates that an individual can attract will have a major affect on their reproductive success. As a result those traits that increase an individual’s chances of attracting potential mates will, all else being equal, tend to spread through the population. Some things selected for in this way will aid survival. But, as Amotz Zahavi has argued, when it

Two problems

At the heart of sexual selection accounts of altruism, as we have seen, is the idea that helping is beneficial because it is a way to demonstrate that we have certain qualities, qualities that members of the opposite sex find desirable in potential mates. How effective helping is at demonstrating these qualities will depend, in part, on the visibility of the help given (at the extreme, helping that no-one knows about does nothing to demonstrate your qualities), and, in part, on the cost of that

Response: a module shaped by sexual selection

In everything that has been said so far we have, I think, been tacitly accepting what is perhaps the standard picture of desire formation. According to this picture—which following Robert Audi we can call motivational foundationalism—there are some things that we want for their own sake (which we can call ‘basic’ desires), and everything else that we want we want as a way to help us to satisfy our basic desires (Audi, 1989, p. 36). There is a tendency to reduce the number of things that we want

Conclusion

It seems, therefore, that whereas sexual selection accounts of the evolution of psychological altruism appear problematic if our minds are non-modular, things are very different if the systems which produce our desires contain modules. In that case motivational systems that would produce altruistic motivation are just the sorts of things that could be sexually selected for. That our desires to help are, at least partly, produced by such mechanisms would also fit with much of our observed

Acknowledgements

I would like to thank Stephen Laurence, Richard Joyce, David Owens and an anonymous reviewer for helpful comments on earlier drafts of this paper, and the Arts and Humanities Research Board for financial support. Versions of this paper have been presented to audiences in Sheffield, Belfast and Canterbury and I am grateful to all those who participated in the discussion on those occasions for their comments and questions.

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