Darwin, Spencer e le varietà umane

Is it possible to individuate in Darwin and Spencer's evolutionistic thinking some form of racist ideology or ethnocentristic prevention? In our paper we will try to answer these questions, which are scarcely analysed by the History of Ideas. More specifically, our intent will be to verify whether the two thinkers — having already conceived decisive theories in biology and philosophy — succeeded in removing the legacy of prejudices, that are hard to die, about the varieties of human species. Furthermore, did Darwin, Spencer (and some other evolutionists) consider these varieties as pegs of a staircase, or as the geographically differentiated result of a same development process?