People are unselfish because they are militaristic, and cultured because they are common. At least that is the message of a couple of new studies. Two of the oddest things about people are morality and culture. Neither is unique to humans,-but Homo sapiens (humans) have both in an abundance missing from other species. (41) ______How these human traits evolved is controversial. But two papers may throw light on the process. In one, Samuel Bowles of the Santa Fe Institute in New Mexico fieshes out his paradoxical theory that much of human virtue was forged in the war. Comrades in arms, he believes, become comrades in other things, too. (42) ______. It also requires a dense population.Dr Bowles’s argument starts in an obscure crack of evolutionary theory called group selection. This suggests that groups of collaborative individuals will often do better than groups of selfish ones, and thus prosper at their expense. (43)______This good-of-the-group argument was widely believed until the 1960s, when it was subject to rigorous scrutiny and found wanting~ The new theory does not pitch groups against groups, or even individuals against individuals, but genes against genes. In fact, this theory does not disallow unselfish behavior. (44)______. The "selfish gene" analysis, so called after a book by Richard Dawkins, makes good-of-the-group theory almost impossible to achieve.Dr Bowles has focused the argument on war, since it is both highly collaborative and often genetically terminal for the losers. In his latest paper he puts some numbers on the idea. He looks at the data, plugs them into a mathematical model of his devising and finds a pleasing outcome.Dr Thomas and his colleagues also rely on a mathematical model. The model suggested that once more than about 50 groups were in contact with one another, the complexity of skills that could be maintained did not increase as the number of groups increased. Rather, it was population density that turned out to be the key to cultural sophistication. (45)______Dr Thomas therefore suggests that the reason there is so little sign of culture until 90,000 years ago is that there were not enough people to support it. According to him, culture was not invented once, when people had become clever enough, and then gradually built up into the edifice it is today. Rather, it came and went as the population waxed and waned. Since the invention of agriculture, of course, the population has done nothing but wax. The consequences are all around you.[A] In the other paper, Mark Thomas and his colleagues at University College, London, suggest that cultural sophistication depends on more than just the evolution of intelligence.[B] It is therefore no surprise, according to group-selectionists, that individuals might be genetically predetermined to act in self-sacrificial ways.[C] But it requires that this evolve in a way that promotes the interest of a particular gene--for example by helping close relatives who might also harbor the gene in question.[D] This, he contends, allows the evolution of collaborative, unselfish traits that would not otherwise be possible.[E] The more people there were, the more exchange there was between groups and the richer the culture of each group became.[F] Indeed, that abundance--of concern for the well-being of others, (even unrelated others), and of finely crafted material objects both useful and ornamental--is seen by many as the mark of man, as what distinguishes humanity from mere beasts.[G] They note the word "almost" in the argument above and contend that humans, with their high intelligence and possession of language, and their tendency to live in small, tightly knit groups, might be exceptional. 45