There is much evidence that both the Namib Desert and the Peruvian-Chilean Desert were formed in the Pleistocene, following the development of a cold southern ocean and westerly circum-arctic winds. These brought winter rain to the southern part of the west coast of Africa. At times, the influence of these winds extended as far as 23°S, so that the winter-rain area of zonobiome IV, now limited to the extreme south, stretched further to the north. Many plant relicts in moist habitats of the highland ridge (Fig. 3.49) bear witness to this former winterrain vegetation; examples are Euclea undulata, Rhus spp., Eriocephalus, Pteronia and Ficus spp. Only when the aridity of the climate increased did the Namib Desert develop, while zonobiome IV was pushed back to the southern tip of Africa (Tankard and Rogers 1978; further literature is cited by Werger 1978). This change in climate was brought about primarily by the development of the cold Benguela current, in the same way as the Peruvian-Chilean Desert is created by the Humboldt current.