Darwin would say that humans, at this point in our evolution, the human species is best served by humans who think about the species first and their individual survival second. The human brain is evolving, changing, from a me first attitude to an us firstattitude. The fittest individuals, at this point in evolution are those who fit in, not those who stand out. Rather than the strong leader of the herd, survival of the fittest now requires strong followers, so to speak, those who prosper most from within the herd. Natural selection will assure that these individuals are the ones to survive.
The fathers of Nulcear fission, Otto Hahn and Fritz Strassmann, would also agree that humans have reached Critical Mass. They would understand that a Chain Reactionis now occurring, and which will continue on its own without the need of individual human input. They would, perhaps, recognize this chain reaction as a phenomenon happening within the human brain and to the way humans think.