Biologically based reassurance depends on reading across from beasts, which are assumed to be ethically homogenous, to human beings, which are assumed to be ethically homogeneous. De Waal argues that, contrary to what many biologically inclined anthropologists and psychologists had argued, Darwinism does not require us to believe that humans are born nasty as a result of being vehicles for our 'selfish genes'. Darwinism allows for cooperative behaviour between individuals of the same species. Hamilton argues that selection takes place at the level of the gene, genetic material maximizes its chances of surviving by making the group in which it is expressed, not the individual, care for itself. The survival of the fittest does not necessarily require the destruction of the less fit by their conspecifics. Non-human primates have many mechanisms to defuse tension, resolve conflicts and heal the social wounds caused by them.