Emporer Penguin Evolution

In so many species, evolution seems to favor male aggression, especially in the behaviors around reproduction. But in the egg warming phase of emperor penguin reproduction, all the guys with eggs on their feet [love writing that] shuffle around so that everyone gets a chance to the warmer inner circle.

At some point in their story there must have been regular guy penguins who tried holding on to the warm inner spot rather than shuffle along. With or without more than one macho 'guin, the ensuing jostling would have broken eggs on the feet of macho guy and otherwise innocent bystanders. [I believe the phrase originates in this context.] So the reproductive edge here favors cooperative males, a nice change of pace from the usual grunt and growl, and so perfectly suited to the penguins' charisma.