Of course the difference between social scientists and journalists is that the former seek predictive power for their theories. The difference between us lies in the question of what constitutes good predictive power.
I believe that the first requisite of a science is that it develop methods appropriate to what it proposes to understand. If we wanted a science that helps us predict earthquakes, we would surely want to know as much as we could about the physical properties of the Earth. If we want to predict how rats will behave, we would accumulate a great deal of experimental data on rats. Our common objective, however, is to understand how human beings behave. A great deal of evidence accumulated through centuries of observation of these creatures suggests that one of the things they do--indeed one of the things that distinguishes them from, say, rats--is use their minds to create cultural artifacts. These artifacts--which include their historical accounts of themselves, their patterns of everyday behavior, their literature, their morality, and even their social science--in turn influence how they act. Human beings, in short, possess an ability to influence the methods that are used to study them in ways that other creatures, both inanimate and living, do not have access to.
You mischaracterize me when you claim that I view science and the humanities in opposition and resent the imperial poachings of the former upon the latter. My point is completely different. It is that the appropriate way of understanding human beings scientifically is to take full account of their humanism. If I want to have some sense of how John is going to behave, I want to know as much about John as possible. If I begin the way you suggest I begin--with a general theory of human nature--what I am likely to discover is that the more I move from a grand level of explanation down to John himself, the more I am going to have to modify such a grand theory to take account of this particular person. So begin wherever you want: with specific biographical details of John or with a theory of human nature. Wherever you begin, you will, if you want to understand John, have to know a great deal about him. None of this means that theory and prediction in social science are impossible. What it does mean is that theory and prediction must be rooted in the actual behavior of real people.
The history of science may be littered with long-forgotten dichotomies, but the history of humans is not. We still talk about the sacred and the profane, the mind and the body, and the natural and the cultural. You predict that someday the last of these dichotomies will be overcome. I have two reactions. One is that you are most probably wrong, since human beings are simultaneously biological and cultural in just about everything they do, and no one has yet made a convincing case that the cultural side of their activities can be reduced to the biological. But the other reaction leaves open the possibility that you may be right. If that turns out to be the case, what a shame it would be that no books like How the Mind Works could be written. For then there would be no mysteries about us to explore that require works of imaginative creativity, literary power, and fascinating interpretation such as yours.
Of course all knowledge is connected. But this does not mean that all knowledge is interchangeable. Our divisions among the sciences, the social sciences, and the humanities long predate the existence of deans--or even of universities. We make such distinctions because we are such multifaceted creatures. We require entire universities so that we can understand ourselves. We created something called science to learn more about how we evolved. We created something called social science to understand how we interact with other human beings. And we created literature, music, art, and religion because something about us always creates new mysteries for us to understand.
No one, certainly not I, argues that we should blinker our intellectual curiosity in the way you suggest. On the contrary, I wish you luck in all your efforts to understand human beings in any way you see fit. I am confident that we who are human will resist all efforts to reduce our behavior to any one thing, which is why I welcome books like yours. When properly read, works influenced by evolutionary psychology leave so much about us unexplained that they reinforce how truly remarkable we who are human happen to be.
Finally, you are right that you cite many empirical studies in your report. My claim about there often being a missing empirical ingredient in the work by evolutionary psychologists was aimed at others, and by including you, I was being unfair.