The Fourth Age, also known as The Age of Reconstruction and The Age of Mortals, was when the surviving races began to rebuild and flourish amongst the world. Heroes from this age include Arrav and Camorra, both of whom have a statue in the Heroes’ Guild.
Aside from a few settlements in the Kharidian Desert and the refugee town of Burgh De Rott (Meiyerditch, although being the largest city with human population at that time, was already ruled by Vampyres by then), most humans in the beginning of the 4th age had abandoned civilization due to destroyed settlements and lived in barbaric tribes. The major exception to this was the city of Saranthium, but this was eventually wiped out.Runescape Gold. As the age progressed, they started to build new and permanent settlements, some of which turned into mighty cities by the late Fourth Age, thus allowing humans to become the dominant race in Gielinor by the end of the Fourth Age.
Humans also attempted to recolonize the Wilderness, but were not successful. Humans would not have become dominant, however, if it were not for the discovery of Rune Essence.