> More to the point, cultures that expand and grow, do so at the expense of cultures that don’t. So through natural selection, we would expect to see more expan

> More to the point, cultures that expand and grow, do so at the expense of cultures that don’t. So through natural selection, we would expect to see more expansionary cultures than non-expansionary cultures. Natural selection cannot apply to societies because there is no reliable mechanism for successful decision-making to propagate itself in the way genes convey successful characteristics to future generations. Does survival depend on expansion? The last century has seen the fragmentation of the imperial world into a proliferation of independent states, big and small. It is now widely recognised that exchange is more profitable than territorial acquisition, and war has become a highly technologically-intensive project bearing exorbitant costs. Most arguments for expansion as a survival strategy would depend upon some version of the realist theory of anarchy, that the absence of a supra-national sovereign creates conditions of mutual insecurity in which states are forced to maximise their relative power. But I would think that any major inter-stellar expansion would require the unification of the world - in some form - removing the realist premise from the argument for super-expansion. > And, even setting aside the argument, you still have the much tougher task of explaining the notion that no extraterrestrial cultures are expansionary, which is what your side of this argument would require. That depends on how common intelligent life is, the maximum possible speed of interstellar travel, the number of ETI that would commit to super-expansion, how good we are (not very) at searching the sky for signs of life, among other things. If you take the upper-bound estimate for most of those categories, then it is not at all paradoxical that we do not see alien life teeming around us.