Abstract
Why did scientific theories on cooperation between organisms only emerge at the end of the XIXth century, when competition and parasitism were already well enough known to have been taken into account by evolutionary theory ? At the time, the notions of mutualism, symbiosis and endosymbiosis came up against Darwin's theory of evolution, and predictions that were not always accurate or verified (endosymbiotic theory, for example) : this slowed down their diffusion, which became conflictual. And yet, from today's point of view, there's no hiatus. It will take the whole of the XXth century to resolve the paradox of cooperation, a delicate balance between costs and benefits, cheaters and altruists. Modern evolutionary theories now explain the persistence of cooperation between living organisms throughout evolution, over longer periods than parasitism.
