Stephen Downes, of The University of Utah Department of Philosophy gave the following presentation to the Humanists of Utah in December 2000

I am going to address the issue of our self understanding, and the philosopher's variant on this, how we explain human behavior. The question I want us to consider is whether biological discoveries force us to change our approach to explaining human behavior.

Some philosophers want to integrate the findings of science with our philosophical understanding, while others resist the findings of science. This is not a new debate. Long before Dewey proposed that Darwin mattered, David Hume had championed Newton as the most important philosopher. Like Dewey, I think that Darwin matters, and so let's briefly consider what he said. In his Descent of Man in 1871, Darwin argued that natural selection was the chief force responsible for producing human traits. From Descent of Man (2nd. Edition, 1874).

We have now seen that man is variable in body and mind; and that the variations are induced, either directly or indirectly, by the same general causes, and obey the same general laws, as with the lower animals. Man has spread widely over the face of the earth, and must have been exposed, during his incessant migration, to the most diversified conditions.

The early progenitors of man must also have tended, like all other animals, to have increased beyond their means of subsistence. They must, therefore, occasionally have been exposed to a struggle for existence, and consequently to the rigid law of natural selection.

If, then, the progenitors of man inhabiting any district, especially one undergoing some changes in its conditions, were divided into two equal bodies, the one half which included all the individuals best adapted by their powers of movement for gaining subsistence, or for defending themselves, would on average survive in greater numbers, and procreate more offspring than the other less well endowed half (48-9).

This argument did not only apply to our bodily traits but also our minds: "We may easily underrate the mental powers of the higher animals, and especially of man, when we compare their actions founded on the memory of past events, on foresight, reason, and imagination, with exactly similar actions instinctively performed by the lower animals; in this latter case the capacity of performing such actions has been gained, step by step, through the variability of the mental organs and natural selection, without any conscious intelligence on the part of the animal during each successive generation" (70).

Darwin argues that we can see that the lower animals have mental powers and behavioral traits that we also display: happiness, bad temper, problem solving behavior and so on. Each of these is accompanied by the same physiological changes in us and the lower animals. Fear, for example, comes along with sweating and increased pulse rate. He argues that our mental traits are derived from those of our precursors and honed by natural selection.

Given this, we should expect to find all manner of biological underpinnings to our behavior. On its face this is not disturbing: our digestive system is a biological system, many features of which we share with other animals and much of our eating behavior can be understood in biological terms. But what about our more sophisticated behavior, behavior that we largely account for in terms of our mental lives. Does this also have an underlying biological explanation? Let's now look at some recent findings in biology that have implications for our self-understanding

The following short story is made up. Any similarities between the characters and people you know is accidental. It is inspired by a recent trip to Sydney, Australia, our fellow Olympic hosts.

Joan and Keith both take the Manley ferry to Sydney every morning on their way to work. Most days it is a beautiful boat ride and provides welcome fresh air before a day in the office. They do not know each other, until one day they notice each other. They start chatting that morning. Look out for each other on future days. They start dating, move in together and eventually marry. Why? Let's look at two answers to this question each derived from different general explanatory accounts of human behavior.

First story, a familiar story (Folk Psychology): Joan is initially attracted to Keith, because he is smart and funny, takes her seriously and laughs at her jokes. She has always wanted a partner who could be a trusted friend and believes that Keith fits that bill. Keith is attracted to Joan, because she is smart and sexy. He believes that Joan is just his type; she seems like the right person for him. All their friends say that they met in such a romantic way that they were sure to stay together. They stay together because they love and respect each other, and their initial beliefs about each others 'qualities are reinforced over the years.

Second story, not so familiar (Chemical Signaling): Joan is attracted to Keith, because she picks up on his direct chemical signaling that indicates that his genes at his MHC locus (major histocompatibility locus) are a good match with Joan's.

Their offspring will be healthy, because they will have a good assortment of genes at the MHC locus. Keith registers Joan's chemical signaling that indicates that her MHC locus is a good match for his for the same reasons. I am sure that we have all heard the first explanation, but what is going on in the second one? Here is some of the background.

Many animals rely on chemical signaling. They communicate with one another via chemical systems that are species specific and can often only be detected by one or other sex. Odors, for example, can be a variation on the theme of attractive plumage in some animals' mating behavior. A female may be more strongly attracted to a male with a certain repertoire of odors, just as a female peacock is more strongly attracted to a male with a fine suit of feathers. Some chemicals involved in signaling are released and detected as odors and others are pheromones. These are odorless chemicals that are known to have specific effects on animal behavior; in vertebrates they are detected by the vomeronasal organ. Chemical signaling plays a role in a wide range of animal behaviors.

Wayne Potts and his collaborators at the University of Utah have done work with house mice that supports some very interesting hypotheses about the role of chemical signaling in mouse reproductive behavior. Specifically, they have established that female mice "might be able to use a male's odor to obtain disease-resistance genes for their offspring by mating with males carrying dissimilar MHC genes" (Penn & Potts, 1998: 394). The MHC genes Potts and Penn refer to are the major histocompatibility genes. These genes code for important immune response mechanisms, and the more heterozygous this gene complex is the wider array of antigens the immune system can recognize. (I follow Penn and Potts' (1999) simplification and use the term "MHC locus" from now on.) Think of the situation like this -- MHC locus illustration -- Now what has all this got to do with us? For many years biologists and psychologists assumed that our odor detection capacities were inferior to most other animals, and researchers also dismissed the idea that there could be human pheromones. Now there is a fair amount of support for the existence of human pheromones and surprising evidence of the role of odors in guiding human pair bonding behavior. This is what is of interest for us today.

Studies have shown that both men and women prefer the odor of MHC dissimilar individuals and further that we tend to marry individuals expressing dissimilar MHC genes (Penn & Potts, 1998). Some of the studies used to elicit these results are called tee-shirt tests. Women are asked to smell tee-shirts that have been worn by different men under specially controlled conditions. Their responses to the relative attractiveness of the odor of the tee-shirts is recorded. Subject's MHC loci are sequenced and hence conclusions can be drawn about the relations between MHC incompatibility and odor preferences. There are several surprising predictions and results about human pair bonding derived from the chemical signaling approach. For example, the approach predicts a higher rate of divorce or separation for couples when the women stops taking the contraceptive pill, if the couple got together when the woman was taking the contraceptive pill. This prediction is derived from the fact that contraceptives can mask the olfactory signal associated with the MHC loci that women prefer. If they made their decision to partner up whilst taking the pill, they are more likely to have ended up with MHC similar individuals. The theory predicts that these women will tend to reject MHC similar mates, as they are less viable parents for their children. Results of MHC sequencing also indicate that people in long lasting marriages are far more likely to be MHC incompatible. And so back to Keith and Joan. They were MHC compatible and lived happily ever after.

For the sake of argument, let's not quibble with the experimental work. Let's assume that it is valid. Many people find these results quite disturbing. When confronted with these results I imagine people thinking "Will our relationship break up when my partner stops taking the pill?" "Will our kids be generally unhealthy as a result of our MHC loci being too compatible?" "Is it worth persisting with a failing relationship or would that be a pointless battle against recalcitrant genes?"

Joking aside, should these results give us pause? If so, what is the proper response to them? I will just point to a few possible directions that could be taken.

I said earlier that the issue at stake is our self understanding, and the philosophical spin on this, which is how we explain others' behavior. First, let's see why philosophers connect these two points. Here is the idea: I understand others by assuming, at least to a good approximation, that they are like me. They have minds and their minds work in ways similar to mine. To understand others and to explain what they do, I appeal to the kinds of mental states I have. Hence the familiar story about Keith and Joan. They have desires, ambitions and needs and we understand how they behave in terms of these mental states. The mental states are used in our explanation. We are now confronted with some questions. For example, what is the best explanation of Keith and Joan's behavior? Let's go back to Darwin for a minute. Darwin developed his views that our mental traits are evolved, and that we share them with other creatures against the background of the criticisms of his contemporaries. One of his most prominent critics was Alfred Wallace. Wallace also proposed evolution by natural selection but backed off from applying the principle to humans, and particularly to human mental traits. Darwin expresses his frustration with Wallace in the Descent of Man: 'I cannot ... understand how it is that Mr. Wallace maintains that "natural selection could only have endowed the savage with a brain little superior to that of an ape"' (49).

Darwin's critics ranged from his friends and fellow travelers, in support of evolution, like Wallace, to theologians and moral theorists. For the most part critics were skeptical that higher mental attributes such as moral sense had any basis in evolution. They argued that once communities had developed to a certain level of sophistication, surely the community itself would provide the direction for intellectual and moral development. Also Wallace argued that what humans required for survival may well be provided by natural selection, but that their highly developed intellectual abilities would have to be accounted for in some other way. The motivation for some criticism was religious or spiritual. Wallace and others began to think that some higher force was necessary to account for the development of our higher faculties.

There are analogous responses to biological accounts of our behavior now. Let's leave worries based on religion to one side. Many argue that biological explanations of our complex behavior cannot possibly take the place of our familiar explanations in terms of our mental life and its implications. The challenge takes many forms. For example, we could ask, "Surely you do not want to say that none of us fall in love?" or worse still "Surely love is not just a chemically based attraction that we share with mice and other creatures?"

The challenges are each given different names by philosophers. We love "isms". The idea that the biological account supercedes the mental one is called eliminativism. One of the implications of scientific advances could be that the new scientific explanation completely replaces the old explanation, in this case in terms of desires and so on. There is no such thing as love; science has shown this. The idea that the biological explanation provides a basis for our previous explanation is called reductionism. Love just is chemical attraction; science has shown this.

I am not sure that either of these responses is the right way to go. This is how I think things stand: On experimental and evolutionary grounds, I am prepared to believe that we have various sophisticated chemical signaling systems. Should we have such systems, there is no reason that we should have any conscious access to their operations and workings. Think, for example, of the digestive system again. We have something of a relationship with the goings on in our guts, but at best we are observers of the passing show. We may stand in a similar type of relation to our chemical signaling systems. They may play some role in directing our behavior and we characterize that behavior in the only terms we know: I believe, I want, I like, I desire, or even I love. Now as Darwin argued there are evolutionary stories about why this is the way that we do things, but we have made far less headway in delivering those. Questions such as, "Where does cognition come from?", "where does language come from?" and "why do humans have both higher cognition and language in larger doses than any other species?" are still awaiting full answers. Answering these questions may help us more readily understand why we explain our own behavior in terms of beliefs and desires and not chemical signals. But answering these questions will not get rid of the fact that we do communicate, to some extent, via chemical signals, and that this kind of signaling provides part of the explanation for the strength of our intimate bonds.

--Stephen Downes