This paper suggests genetic proximity, in addition to geographic proximity and imports, as a factor facilitating international knowledge transmission, where knowledge is measured as the stock of knowledge as well as research intensity to allow for the possibility that international knowledge spillovers have permanent productivity growth effects. Using data for 31 countries with diverse development paths over the period 1870–2011, the results show that genetic proximity and imports are important in facilitating knowledge transmission, and that knowledge spillovers have permanent growth effects.