During the last 50 years, life sciences seemed to demonstrate that utilitarianism was the only possible evolutionary pathway, closing the debate in social sciences. The latest converging results of studies using more complexe, less biaised models and behavioural experiments suggest today that this hypothesis was fundamentally wrong: humans are neither rational nor perfectly selfish. This non-utilitarianism of Human Beings is also a characteristic of primitive life forms: cooperation has existed since the origine of life and could even be one of the fundamental motors of evolution. The recent parallel discovery of various mecanism allowing the apparition and survival of cooperation in a context of postulated selfish genes revitalizes a 100 years old sociological debate.