The mostly northern hemisphere distribution of Pteridium aquilinum sensu stricto vs. the mostly southern hemisphere distribution of the remaining diploid species in the genus is suggestive of a Laurasian/Gondwanan split, however, there is no fossil evidence to directly confirm the development this biogeographic pattern. Currently, there is a large area of geographic overlap between the two groups in Latin America and portions of southern Asia. Rymer (1973) reviewed the fossil history of Pteridium. The oldest macrofossils attributed to the genus date to the Oligocene of Hungary, and unequivocal leaf compressions of Pteridium have been recorded from the late Miocene of England and late Pliocene of New Zealand (Oliver, 1928). Rymer reviewed the Quaternary history of Pteridium in Great Britain in somewhat more detail, noting that its distribution waxed and waned during successive glacial and interglacial stages, and that generally the current distribution of P. aquilinum is a relatively recent phenomenon affected greatly by prehistoric and historic human-mediated perturbations such as clearing of forests and introduction of livestock.