In the merciless arena of life, we are all subject to the law of the jungle, to ruthless competition and the survival of the fittest - such is the myth that has given rise to a society that has become toxic for our planet and for our and future generations. But today the lines are shifting. A growing number of new movements and thinkers are challenging this skewed view of the world and reviving words such as `altruism', `cooperation', `kindness' and `solidarity'. A close look at the wide spectrum of living beings reveals that, at all times and in all places, animals, plants, microorganisms and human beings have practised different forms of mutual aid. And those which survive difficult conditions best are not necessarily the strongest, but those which help each other the most. Pablo Servigne and Gauthier Chapelle explore a vast, forgotten continent of mutual aid in order to discover the mechanisms of this `other law of the jungle'. In so doing, they provide a more rounded view of the world of living things and give us some of the conceptual tools we need to move beyond the vicious circle of competition and self-destruction that is leading our civilization to the verge of collapse.