As man advances in civilisation, and small tribes are united into larger communities, the simplest reason would tell each individual that he ought to extend his social instincts and sympathies to all the members of the same nation, though personally unknown to him. This point being once reached, there is only an artificial barrier to prevent his sympathies extending to the men of all nations and races (vol. 1, pp. 100-101).The 'artificial barrier' Darwin would have humans leap is the barrier that separates social organization among competing human groups from a social organization that contains all human beings within a single group. Is it theoretically inconceivable that human beings could extend their sense of group identity to the human species as a whole? From within the woridview established by modern evolutionary theory, any such extension would have to accommodate itself to the largest principle that regulates all of life—the principle of inclusive fitness.
The principle of inclusive fitness, as it is currently understood by evolutionary psychologists does not require us to suppose that all individuals at all times are seeking to maximize their reproductive advantage. Instead, it requires us to suppose that all individuals at all times are operating under the constraints of an evolved psychology that is itself the product of a process of adaptation that has been regulated, throughout the history of life, by the principle of inclusive fitness. The difference is not small. Human beings have evolved a complex set of psychological dispositions, including cognitive and social dispositions, precisely because these dispositions have helped to ensure their reproductive success over millions of years. Reproductive success is thus an ultimate causal force, but the evolved psychological dispositions are themselves proximate causes that are often only indirectly related to the immediate purposes of reproduction. To achieve a world order dominated by universal sympathy would thus not require that the reproductive interests of every individual be harmonized with those of every other individual. It would require, instead, that the evolved psychological dispositions of every individual be harmonized with the evolved psychological dispositions of all other individuals. (On proximate and ultimate cause, see Barkow, 1989, p. 296; Betzig, 1991, p. 140; Symons, 1979, p. 261; Tooby and Cosmides, 1992, p. 54.)
Given the regulative principle of inclusive fitness, organisms animated exclusively by a selfless, self-sacrificing sympathy to other organisms could not have evolved and in fact have not evolved. As Richard Dawkins observes, 'Much as we might wish to believe otherwise, universal love and the welfare of the species as a whole are concepts that simply do not make evolutionary sense' (1989, p. 2). Sympathy is only one human motive among others, and all of human history provides us with abundant evidence that under the stimulus of desire, fear, or even simple conformism, this one motive can be easily overridden. Consequently—barring an elementary genetic restructuring of our evolved human psychology—in order to achieve a state in which individual and collective interests were fully synchronized, the evolved psychological dispositions of all individuals would have to be wholly under the administrative direction of a political authority possessing perfect control of all variable factors. This authority would have to be able to regulate the phenotypic interaction of the coordinated mass of individual human beings with all environmental stimuli, and it would have to be sufficiently flexible to anticipate and assimilate all further evolutionary developments emerging from the continuing interaction of random variation and selective retention. While the agents of political authority would thus have to possess perfect control of all variable factors, they would themselves have to be sufficiently constrained by internalized moral sanctions so that they could be trusted not to abuse the powers placed in their hands. (If they were constrained only by external social forces, they would not possess the perfect control necessary to regulate the whole system.)
It should be evident that the biological conditions that would have to be satisfied in order to achieve a Utopian world order are of such extreme difficulty as to be, for all practical purposes, unreachable. It is hardly surprising, then, that these conditions are exceedingly remote from the conditions that actually prevail in the world in which we now live. These actual conditions include a good deal of xenophobia and virulent racial, ethnic, national, religious, and ideological hostility, and all this hostility, arising out of various forms of group identity, should alert us to a psychological difficulty inherent in the very idea of a universal brotherhood. Richard Alexander identifies the difficulty. Commenting on efforts to find a solution for nuclear war, Alexander observes that 'systems of morality' arise from 'within-group altruism' (1987, p. 233). The argument for '"universal brotherhood"' presupposes 'that we can achieve peace and prevent war' by expanding this within-group altruism 'so as to include the whole world.' But any such expansion would obviate the conditions under which the systems of morality arose in the first place. Expectations of universal brotherhood 'ignore or seek to override the paradox that extreme within-group altruism seems to correlate with and be historically related to between-group strife' (p. 233).