that the figure is around 100,000 to 200,000. Bryan Ward-Perkins also argues for up to 200,000 incomers. Catherine Hills suggests the number is nearer to 20,000. A computer simulation showed that a migration of 250,000 people from mainland Europe could have been accomplished in as little as 38 years. Recent genetic and isotope studies have suggested that the migration, which included both men and women, continued over several centuries, possibly allowing for significantly more new arrivals than has been previously thought. By around 500, communities of Anglo-Saxons were established in southern and eastern Britain. Härke and Michael Wood estimate that the British population in the area that eventually became Anglo-Saxon England was around one million by the start of the fifth century; however, what happened to the Britons has been debated. The traditional explanation for their archaeological and linguistic invisibility is that the Anglo-Saxons either killed them or drove them to the mountainous fringes of Britain, a view broadly supported by the few available sources from the period. However, there is evidence of continuity in the systems of landscape and local governance, decreasing the likelihood of such a cataclysmic event, at least in parts of England. Thus, scholars have suggested other, less violent explanations by which the culture of the Anglo-Saxons, whose core area of large-scale settlement was likely restricted to what is now southeastern England, East Anglia and Lincolnshire, could have come to be ubiquitous across lowland Britain. Härke has posited a scenario in which the Anglo-Saxons, in expanding westward, outbred the Britons, eventually reaching a point where their descendants made up a larger share of the population of what was to become England. It has also been proposed that the Britons were disproportionately affected by plagues arriving through Roman trade links, which, combined with a large emigration to Armorica, could have substantially decreased their numbers. Even so, there is general agreement that the kingdoms of Wessex, Mercia and Northumbria housed significant numbers of Britons. Härke states that "it is widely accepted that in the north of England, the native population survived to a greater extent than the south," and that in Bernicia, "a small group of immigrants may have replaced the native British elite and took over the kingdom as a going concern." Evidence for the natives in Wessex, meanwhile, can be seen in the late seventh century laws of King Ine, which gave them fewer rights and