It is not the aim of this essay to offer the reader a long list of ideas, facts, institutions, or scientific processes, which are more likely to be found elsewhere, in more painstaking chronological order.¹ Instead, the purpose of this article is to look back at a body of scientific ideas that appeared in the 1880s and which assisted in the birth and development of an evolutionist mentality at the very core of the Argentine intellectual and political elite, within the general frame of a more extensive ideology: thus, the idea of Progress.