The God Delusion
GROUP SELECTION
Some alleged ultimate explanations turn out to be - or avowedly are - 'group-selection' theories. Group selection is the controversial idea that Darwinian selection chooses among species or other groups of individuals. The Cambridge archaeologist Colin Renfrew suggests that Christianity survived by a form of group selection because it fostered the idea of in-group loyalty and in-group brotherly love, and this helped religious groups to survive at the expense of less religious groups. The American group-selection apostle D. S. Wilson independently developed a similar suggestion at more length, in Darwin's Cathedral.
Here's an invented example, to show what a group-selection theory of religion might look like. A tribe with a stirringly belligerent 'god of battles' wins wars against rival tribes whose gods urge peace and harmony, or tribes with no gods at all. Warriors who unshakeably believe that a martyr's death will send them straight to paradise fight bravely, and willingly give up their lives. So tribes with this kind of religion are more likely to survive in inter-tribal warfare, steal the conquered tribe's livestock and seize their women as concubines. Such successful tribes prolifically spawn daughter tribes that go off and propagate more daughter tribes, all worshipping the same tribal god. The idea of a group spawning daughter groups, like a beehive throwing off swarms, is not implausible, by the way. The anthropologist Napoleon Chagnon mapped just such fissioning of villages in his celebrated study of the 'Fierce People', the Yanomamo of the South American jungle.77
Chagnon is not a supporter of group selection, and nor am I. There are formidable objections to it. A partisan in the controversy, I must beware of riding off on my pet steed Tangent, far from the main track of this book. Some biologists betray a confusion between true group selection, as in my hypothetical example of the god of battles, and something else which they call group selection but which turns out on closer inspection to be either kin selection or reciprocal altruism (see Chapter 6).
Those of us who belittle group selection admit that in principle it can happen. The question is whether it amounts to a significant force in evolution. When it is pitted against selection at lower levels - as when group selection is advanced as an explanation for individual self-sacrifice - lower-level selection is likely to be stronger. In our hypothetical tribe, imagine a single self-interested warrior in an army dominated by aspiring martyrs eager to die for the tribe and earn a heavenly reward. He will be only slightly less likely to end up on the winning side as a result of hanging back in the battle to save his own skin. The martyrdom of his comrades will benefit him more than it benefits each one of them on average, because they will be dead. He is more likely to reproduce than they are, and his genes for refusing to be martyred are more likely to be reproduced into the next generation. Hence tendencies towards martyrdom will decline in future generations.
This is a simplified toy example, but it illustrates a perennial problem with group selection. Group-selection theories of individual self-sacrifice are always vulnerable to subversion from within. Individual deaths and reproductions occur on a faster timescale and with greater frequency than group extinctions and fissionings. Mathematical models can be crafted to come up with special conditions under which group selection might be evolution-arily powerful. These special conditions are usually unrealistic in nature, but it can be argued that religions in human tribal groupings foster just such otherwise unrealistic special conditions. This is an interesting line of theory, but I shall not pursue it here except to concede that Darwin himself, though he was normally a staunch advocate of selection at the level of the individual organism, came as close as he ever came to group selectionism in his discussion of human tribes:
When two tribes of primeval man, living in the same country, came into competition, if the one tribe included (other circumstances being equal) a greater number of courageous, sympathetic, and faithful members, who were always ready to warn each other of danger, to aid and defend each other, this tribe would without doubt succeed best and conquer the other . . . Selfish and contentious people will not cohere, and without coherence nothing can be effected. A tribe possessing the above qualities in a high degree would spread and be victorious over other tribes; but in the course of time it would, judging from all past history, be in turn overcome by some other and still more highly-endowed tribe.78
To satisfy any biological specialists who might be reading this, I should add that Darwin's idea was not strictly group selection, in the true sense of successful groups spawning daughter groups whose frequency might be counted in a metapopulation of groups. Rather, Darwin visualized tribes with altruistically co-operative members spreading and becoming more numerous in terms of numbers of individuals. Darwin's model is more like the spread of the grey squirrel in Britain at the expense of the red: ecological replacement, not true group selection.