Abstract
Why did scientific theories addressing cooperation between organisms emerge only at the end of the 19 XIXth, even though competition and parasitism were already well-known enough to have been incorporated into evolutionary theory At that time, the concepts of mutualism, symbiosis, and endosymbiosis clashed with Darwin’s theory of evolution and with predictions that were not always accurate or verified (the endosymbiotic theory, for example) this slowed their spread, making it contentious. Yet, from today’s perspective, there was no gap. It would take the entir XXthth 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 among living organisms throughout evolution, over time spans longer than those of parasitism.
