Sweden's prehistory begins in the Allerød oscillation, a warm period around 12,000 BC,[23] with Late Palaeolithic reindeer-hunting camps of the Bromme culture at the edge of the ice in what is now the country's southernmost province, Scania. This period was characterised by small clans of hunter-gatherers who relied on flint technology.[24] Sweden and its people were first described by the Roman historian Publius Cornelius Tacitus in his Germania (98 AD).[25] In Germania 44 and 45 he mentions the Swedes (Suiones) as a powerful tribe with ships that had a prow at each end (longships).[26] Which kings (*kuningaz) ruled these Suiones is unknown, but Norse mythology presents a long line of legendary and semi-legendary kings going back to the last centuries BC. The runic script was in use among the south Scandinavian elite by at least the second century AD, but all that has survived from the Roman Period is curt inscriptions demonstrating that the people of south Scandinavia spoke Proto-Norse at the time, a language ancestral to Swedish and other North Germanic languages.[27] In the sixth century, the Byzantine historian Jordanes names two tribes living in Scandza, both of which are now considered to be synonymous with the Swedes: the Suetidi and Suehans.[28] The Suehans were known to the Roman world as suppliers of black fox skins and, according to Jordanes, had very fine horses, similar to those of the Thyringi of Germania ("alia vero gens ibi moratur Suehans, quae velud Thyringi equis utuntur eximiis"). Viking Age See also: Early Swedish history, Consolidation of Sweden, and Varangians Viking expeditions (blue lines) The Swedish Viking Age lasted roughly from the eighth century to the 11th century. It is believed that Swedish Vikings and Gutar mainly travelled east and south, going to Finland, Estonia, the Baltic countries, Russia, Belarus, Ukraine, the Black Sea and even as far as Baghdad. Their routes passed through the Dnieper south to Constantinople, on which they carried out numerous raids. The Byzantine emperor Theophilos noticed their great skills in war and invited them to serve as his personal bodyguard, known as the Varangian Guard. The Swedish Vikings, called Rus, are believed to be the founders of Kievan Rus'.[29] The Vikings were described by many outside sources, such as the Arab traveler Ibn Fadlan.[30] The actions of these Swedish Vikings are commemorated on many runestones in Sweden, such as the Greece runestones and the Varangian runestones. There was also considerable participation in expeditions westwards, which are commemorated on stones such as the England runestones. The last major Swedish Viking expedition appears to have been the ill-fated expedition of Ingvar the Far-Travelled to Serkland, the region south-east of the Caspian Sea. Its members are commemorated on the Ingvar runestones, none of which mentions any survivor.[31] The Tjängvide image stone dating from 800 to 1099, example of Viking art During the early stages of the Viking Age, a centre of trade in northern Europe developed at Birka on the island of Björkö, not far from where Stockholm was later constructed, in mid-latitude Sweden. Birka was founded around 750 AD as a trading port by a king or merchants trying to control trade.[32] Birka was the Baltic link in the Dnieper trade route through Ladoga (Aldeigja) and Novgorod (Holmsgard) to the Byzantine Empire and the Abbasid Caliphate.[33] It was abandoned around 975, at about the same time Sigtuna was founded as a town some 35 km to the northeast. It has been estimated that the population in Viking Age Birka was between 500 and 1000 people.[32] Archaeological finds indicate that Birka still was wealthy in the 9th and 10th centuries. Thousands of graves, coins, jewelry and other luxury items have been found there.[34] Kingdom of Sweden A rough map of the extent of Swedish rule, c. 1280 The actual age of the kingdom of Sweden is unknown.[35] Determining its age depends mostly on whether Sweden is considered a nation when the Svear (Swedes) ruled Svealand or when the Svear and the Götar (Geats) of Götaland were united under a single ruler. In the former case, Svealand was first mentioned as having one single ruler in the year 98 by Tacitus, but it is almost impossible to know for how long it had been this way. The epic poem Beowulf describes semi-legendary Swedish-Geatish wars in the sixth century. However, historians typically start the line of Swedish monarchs from when Svealand and Götaland were ruled under the same king, namely Erik the Victorious and his son Olof Skötkonung in the tenth century. These events are often described as the consolidation of Sweden, although substantial areas were conquered and incorporated later. In this context, "Götaland" primarily refers to the provinces of Östergötland and Västergötland. Småland was of little interest at the time due to its deep pine forests, with only the city of Kalmar and its castle holding any significant importance. There were also Swedish settlements along the southern coastline of Norrland, one of the four lands of Sweden.[36] Saint Ansgar is traditionally credited with introducing Christianity to Sweden in 829, but the new religion did not begin to fully replace paganism until the 12th century. During that century, Sweden was undergoing dynastic struggles between the Erik and Sverker clans. The conflict ended when a third clan married into the Erik clan, founding the Bjälbo dynasty, which gradually consolidated Sweden into a stronger state. According to the Legend of Saint Erik and the Erik's Chronicle, Swedish kings conducted a series of Crusades to pagan Finland and started conflicts with the Rus', who by then had no further connections with Sweden.[37] As a result of the Crusades, mostly with the Second Swedish Crusade led by Birger Jarl[38] Finland gradually became part of the kingdom of Sweden and the sphere of influence of the Catholic Church.[39] The Swedes built fortresses in Tavastland and Åbo, while a Swedish royal council was instituted, an administrative structure and fiscal apparatus was created, and law codes were codified during the reigns of Magnus Ladulås (1275–1290) and Magnus Eriksson (1319–1364).[40] As a result, the Finnish lands were firmly integrated into the Swedish realm.[41] Except for the provinces of Scania, Blekinge, and Halland in the southwest of the Scandinavian peninsula, which were part of the Kingdom of Denmark during this period, feudalism never developed in Sweden as it did in much of Europe.[42] As a result, the peasantry remained largely a class of free farmers throughout most of Swedish history. Slavery, also known as thralldom, was not common in Sweden,[43] and the institution gradually diminished due to the spread of Christianity, the difficulty of obtaining slaves from lands east of the Baltic Sea, and by the development of cities before the 16th century.[44] Indeed, both slavery and serfdom were abolished altogether by a decree of King Magnus Eriksson in 1335. Sweden remained a poor and economically underdeveloped country, where barter was the primary means of exchange.[45] In 1319, Sweden and Norway were united in a personal union under King Magnus Eriksson, the grandson of King Magnus Ladulås of Sweden and of King Haakon V of Norway. Magnus Eriksson also ruled Scania from 1332 to 1360. In the mid-14th century, Sweden was struck by the Black Death.[46] The population of Sweden and most of E