Ancient environmental and sea-level changes are very likely to have played key roles in primate speciation, extinction, adaptation, and dispersal. Most modern primates are ecologically dependent on trees and inhabit tropical environments, and the same was true for many extinct primates. In the warm Paleocene and Eocene when the tropical broadleaf forest biome extended to high latitudes, primates inhabited North America and northern Eurasia. Ranges then contracted into lower latitudes in the Eocene and Oligocene when global cooling caused a commensurate reduction in suitable tree cover, only to expand again in the Miocene, when most primates across Africa, Eurasia, and South America exploited diverse forest and woodland environments, which may have been very different to those observed in similar regions today. By the end of the Miocene through to the Pleistocene, grassland expansion allowed more terrestrial and open habitat primates to radiate, although most retained some ecological dependence on trees. Sea-level changes occurring since the origin of primates, causing events such as the closure of the eastern Tethys Sea, appearance of the Isthmus of Panama, and shifts in Southeast Asian archipelagos, influenced primate dispersal and diversification. Changes to ocean circulation caused by sea-level change may have impacted global climate, which in turn would have altered primate environments.
Elton, S. (2017). Palaeoenvironmental and sea-level change. In A. Fuentes (Ed.), The international encyclopedia of primatology. John Wiley and Sons. https://doi.org/10.1002/9781119179313.wbprim0481