So the zero-sum competition drives the growth in non-zero-sum ones, and it has long been this way. So when two chiefdoms or two ancient states would compete or whatever, the way to succeed in the competition was to help people within their organisation collaborate more effectively. And that doesn't mean that there are no zero-sum games within those organisations; there are: there are rivalries, there is exploitation and all of that. But still, fundamentally to succeed in these zero-sum games you need to be good at the non-zero-sum games.
And that actually, you mentioned Darwin, that's true with the biological organisation as well. The organisms that are favoured by natural selection could be described as organisations within which there are non-zero-sum game dynamics among the cells, among the organs. So a given individual is in a way a bunch of cells playing a non-zero-sum game with one another, because they have 'a common interest'. Not that they think about it, but because they share the same DNA, getting the DNA into the next generation is in a certain sense a common goal.
So in biological evolution and cultural evolution, in a way you have the same fundamental dynamic: that yes, there is zero-sum-games competition, but that competition drives the system to create new forms of non-zero-sum collaboration.