Consolidation of Sweden

The consolidation of Sweden involved an extensive process during which the loosely organized social system consolidated under the power of the king. The actual age of the Swedish kingdom is unknown. Also, for various reasons, scholars differ in defining early Sweden as either a country, state or kingdom.
Unlike the histories of Denmark and Norway, there is no agreement on a reliable date for a unified Sweden. Historians judge differently the sources for the history of Sweden's consolidation. The earliest history blends with Norse mythology. Early primary sources are foreign; secondary sources were written at a later date.
Older sources.
Based on the origins of the name of the kingdom as meaning (Kingdom of the Swedes), some historians have argued that Sweden was unified when the Swedes first solidified their control over the regions they were living in. The earliest date for this is based on a brief section in the Roman historian Tacitus discussing the Suiones tribe. 
This would imply that a Swedish kingdom would have existed in the first to second centuries AD. However, with the increased rigour of historical method advanced in 20th century historical research, in Sweden as elsewhere, historians such as Curt Weibull and his brother Lauritz maintained that these perspectives have become obsolete. Modern historians noted that a millennium had passed between Tacitus and more in-depth and reliable documented accounts (or notices of contemporary events relating to Sweden by Frankish and German writers) of Swedish history. The work of Birger Nerman (1925), who argued that Sweden held a senior rank among the existing European states at the time represents a nationalist reaction to the academic historiography, with the latter taking a critical or cautious view of the value of old layers of sources of history especially if these documents and traditions are unsupported by any direct traces, any footprint of events and social or political conditions in the archaeological records, buildings, coinage etc. of the age in question.
Geats-Swedes arguments.
The names Swedes and Geats are attested in the Old English poems "Beowulf" (written down in the 11th century) and "Widsith" (from the 8th century) and building on older legendary and folklore material collected in England. In both poems, an Ongentheow (corresponding to "Angantyr" in Icelandic sagas) is named as the King of the Swedes, and the Geats are mentioned as a separate people. These names of peoples living in present-day Sweden, the Anglo-Saxon references and now lost tales they were attached to must have travelled across the North Sea. The first time the two peoples are documented to have had a common ruler is during the reign of Olof Skötkonung about AD 1000. <ref> name="NE">