The resort to biological “analogies”, “metaphors” and “concepts” is an important aspect of the history of the relationships between economics and biology and has long been greatly controversial. This controversy continues today in the most recent work of three cliometricians, i.e. Fogel (post 1982) and Ashraf and Galor (2013). We focus on the theories of historical growth relying on biological explanations which have been formulated by these economists, from the specific angle of biological reductionism. We propose a methodological critique of their use of biological variables as determinants of the historical dynamics of economic growth. Based upon the transposition to the field of economics of Ernst Mayr’s distinction between functional and evolutionary biology and his definitions of reductionism, we argue that despite some similarities, the questions raised by Fogel’s and Ashraf & Galor’s theories are of distinct nature. Nonetheless, we stress the need for a careful examination of the biological mechanisms supporting these researches.