Since formalization of plate tectonic theory in the 1960s, vicariance has been the dominant model for interpretation in biogeography. However, modern research suggests transoceanic ‘rafting’ is also an important process in biological dispersal. Here we show that Cenozoic occurrences of rafting-associated colonization of new lands by terrestrial biota are not randomly distributed in time, but cluster at c. 40 million years ago (Ma) and c. 15 Ma. These excursions in rafting activity are reflected across taxonomic groups and ocean basins. The global scale and ~25 million-year (My) wavelength of the fluctuations suggest they are associated with planetary-scale changes and/or events.