William D. Hamilton's Brazilian lectures and his unpublished model regarding Wynne-Edwards's idea of natural selection. With a note on 'pluralism' and different philosophical approaches to evolution.

In 1975, the English evolutionist William Donald Hamilton (1936-2000) held in Brazil a series of lectures entitled "Population genetics and social behaviour". The unpublished notes of these conferences-written by Hamilton and recently discovered at the British Library-offer an opportunity to reflect on some of the author's ideas about evolution. The year of the conference is particularly significant, as it took place shortly after the applications of the Price equation with which Hamilton was able to build a model that included several levels of selection. In this paper I mainly analyse the inaugural lecture in which Hamilton proposes a simple model to disprove the hypothesis supported by the British zoologist C. Vero Wynne-Edwards (1906-1997) regarding mechanisms to prevent "over-exploitation of the food supply" in "the interests of the survival of the group". The document presented here is of great historical interest. Not only because manuscript offers a model that-since it was intended for teaching purposes-had never before appeared in the published version, but also because of the general index of the lectures that accompanies it. The latter allows us to make some hypothetical considerations on the relationship and differences between kin-selection, group-selection and inclusive fitness that Hamilton wanted to present to the attentive, well-prepared audience of the foreign university that had invited him.