Sociability and need of mutual aid and support are such inherent parts of human nature that at no time of history can we discover men living in small isolated families, fighting each other for the means of subsistence. On the contrary, modern research, as we saw it in the two preceding chapters, proves that since the very beginning of their prehistoric life men used to agglomerate into gentes, clans, or tribes, maintained by an idea of common descent and by worship of common ancestors.