Abkhazians are probably aboriginal to the area. The landscape is rich in archaeological sites dating back to the Paleolithic period, notably the thousands of dolmens (burial structures built of stone slabs, often weighing many tons) dating from the end of the third millennium B.C. Abkhazia later formed part of the Colchis Kingdom, famous in ancient Greek literature as "the Land of the Golden Fleece." This kingdom, which reached its peak between about 900 and 800 B.C. , was apparently a leader in developing bronze- and ironworking technology. The Greeks colonized Abkhazia in the 6th and 5th centuries B.C. , founding Sukhum (now Sukhumi) and establishing themselves as traders. (Using Greek and Near Eastern sources, historians have traced Abkhazian political and social history back to this time; later—in the first and second centuries A.D. —they are referred to in the works of Pliny the Elder and Arrian, respectively.) The country was subordinate first to the Roman and then to the Byzantine empires and converted to Christianity about 543-546 (in the reign of Justinian I); however, neither empire exercised consistent, strong control in Abkhazia, and there were several uprisings (e.g., in the 550s). Between the third and sixth centuries, Abkhazia developed a feudal system similar to that of Europe, although all free men and women bore arms and the gap between princes and commoners was modest. Abkhazians escaped the worst of the Arab invasions (seventh-eighth centuries), and with the waning of Byzantine influence in the Caucasus in the late eighth century, they emerged as a regional military power, notably from the eighth to the tenth centuries in the so-called Abkhazian Kingdom. In 1008, the Armenian-connected line of the House of Bagration united the Abkhazian and Georgian thrones, although war and intrigue continued among the region's princely families. The two kingdoms were legally coordinate, but the Georgian language came to replace Greek in the liturgy. In general, Abkhazia as a separate political and cultural entity was eclipsed during the following several hundred years by an ascendant Georgian Empire. With the Ottoman invasion in the fifteenth century (about 1451), this empire again splintered into small kingdoms and principalities in shifting alliances. Islam was now gradually adopted by some Abkhazians, who first formed part of an unstable West Georgian state (sixteenth century) and then became basically independent (seventeenth century). Many times during the eighteenth century the Abkhazians assisted the Georgian efforts to throw out the Turks even while the Russian presence was growing. The competing influence of Russians and Turks ended in 1810, when the dukes of Abkhazia yielded Sukhum, and Abkhazia itself became a Russian protectorate; in 1864 it became directly subject to Russian rule. By 1870 the Russian government had emancipated Abkhazian serfs and slaves; however, most of these peasants already believed they owned their land, and they resented having to pay indemnities. This resentment led to several rebellions and continuing social and economic instability until 1912, when all such debts were canceled. In the meantime, though, the majority of Abkhazians (like many other northwestern Caucasians) had accepted Turkey's offer of sanctuary in a fellow Islamic country and had emigrated, despite the fact that most of them were only nominally Muslim. In Turkey they were given poor land or none at all, they felt homesick and deceived, and they died in large numbers. During and after the Russian Revolution there was fierce fighting in Abkhazia, often involving close Abkhazian cooperation with Georgian Communists and class conflict within Abkhazia itself. Georgian Mensheviks destroyed a short-lived commune in 1918. Nevertheless, Bolsheviks reestablished their power and the Abkhazian SSR became allied with the Georgian SSR. Both entered the Transcaucasian Federation in 1922; by 1931, however, Abkhazia had become an autonomous republic within the larger Georgian entity. A policy of Georgianization, initiated under the Mensheviks, was later pursued by Joseph Stalin and the Bolshevik leaders in Georgia: L. Beria (1931-1938), Chark'viani (1938-1952), and A. Mgeladze (1952-1953). The government never carried out its plans to transport the Abkhazians to Central Asia in the late 1940s, despite pseudoscholarly articles that claimed that the Abkhazians had only resided in their homeland since the seventeenth century. Large-scale, sometimes forced migrations of other groups into Abkhazia reduced the native percentage of the population, and the closure of Abkhaz-language schools and a prohibition against publishing in Abkhaz temporarily weakened the status of the language.