The Norse chieftain Ingólfr Arnarson built his homestead in present-day Reykjavík in the year 874. Ingólfr was followed by many other emigrant settlers, largely Scandinavians and their thralls, many of whom were Irish or Scottish.[22] By 930, most arable land on the island had been claimed; the Althing, a legislative and judicial assembly, was initiated to regulate the Icelandic Commonwealth. Lack of arable land also served impetus to the settlement of Greenland starting in 986.[23] The period of these early settlements coincided with the Medieval Warm Period, when temperatures were similar to those of the early 20th century.[24] At this time about 25% of Iceland was covered with forest compared to 1% in the present day.[25] Christianity was adopted by consensus around 999–1000, although Norse paganism persisted among some segments of the population for some years afterwards.