A major flaw of our knowledge of the Viking Age is the fact that theirs was an oral society, where the only written documents were runic inscriptions. These are often short and formulaic, offering limited understanding of Viking affairs. There is a problematic lack of contemporary sources from the Vikings themselves.

The contemporary sources that we do have are from other peoples, such the Western Europeans who suffered Viking raids. The sources from the Norse themselves, mainly the sagas from Iceland, were written down well into Christian times by descendants of Vikings. Thus almost all literary sources are written through the lenses of strangers.

For the period before the Viking Age, what you're addressing in your question, we know even less. (I will limit the scope to the centuries immediately preceding the Viking Age and not begin with the end of the ice age.) Some of the sagas describe ancient kings, but these are believed to be mainly stories told without actual knowledge of ancient events, more representative of the time of their creation than pre-Viking Scandinavia. There have been mentions and descriptions of Germanic tribes since Roman times, but these are more in the vein of rumors of faraway lands.

This is an excerpt from 6th century Roman Jordanes' Getica, a history of the Goths. He writes about the different peoples on the "island of Scandza":

"But still another race dwells there, the Suehans, who, like the Thuringians, have splendid horses. Here also are those who send through innumerable other tribes the sapphire colored skins to trade for Roman use. They are a people famed for the dark beauty of their furs and, though living in poverty, are most richly clothed. Then comes a throng of various nations, Theustes, Vagoth, Bergio, Hallin, Liothida. All their habitations are in one level and fertile region. Wherefore they are disturbed there by the attacks of other tribes. Behind these are the Ahelmil, Finnaithae, Fervir and Gauthigoth, a race of men bold and quick to fight. Then come the Mixi, Evagre, and Otingis. All these live like wild animals in rocks hewn out like castles. And there are beyond these the Ostrogoths, Raumarici, Aeragnaricii, and the most gentle Finns, milder than all the inhabitants of Scandza. Like them are the Vinovilith also. The Suetidi are of this stock and excell the rest in stature. However, the Dani, who trace their origin to the same stock, drove from their homes the Heruli, who lay claim to preeminence among all the nations of Scandza for their tallness."

Some of the names of these tribes are understood by us; Suehans and Suetidi are believed to be Swedes, whereas the Dani are Danes. However, many others are unrecognizable. It is a glimpse into a mysterious world that creates more questions than it answers.

What we need to do is to look to archaelogy. These times in Scandinavia are pre-historical. While the contemporary Romans were aware of Germanic tribes far to the north, they did not know (or care) much.

In archaelogy we find farms and large manor buildings known as halls. Towns, however, only started to form just before or during the start of the Viking Age. In the 8th century there was Birka in Sweden and Ribe in Denmark. If we divide things into "pre-Viking" and "Viking", these towns go into the latter category. If we disregard the British view of a Viking Age beginning in 793 due to the raid of the monastery at Lindisfarne, the Scandinavian Iron Age can be seen as a more natural progression. Some Viking towns grew out of earlier market places, whereas others were founded.

Smaller than towns, there were settlements, that occasionally lasted for centuries. Some are referred to as central places, linked not only with the exercise of power but also to cult activity and metalcrafting. One example is Uppåkra in Sweden, inhabited during almost the entire first millenium AD. Here we might speak of an Iron Age town. In Lejre, Denmark, a great hall once stood. Before the larger, Viking era hall there were earlier ones, the first from the 6th century. (This could be Heorot, the great hall from Beowulf.)

By these settlements a great number of objects have been found, for example a 6th century glass bowl in Uppåkra thought to originate in present-day Ukraine. They are further evidence of widespread trade across Europe, as are the large quantities of Arabic silver coins. The giving of gifts is thought to have been an important aspect of maintaining relationships. The practice of depositing hoards of gold and other valuables is believed to have had religious significance. Hoards can be found either near buildings or by the intersection of land and water, possibly a sacrifice to supernatural powers or gods.

Most burials at the time were cremations and grave goods are generally damaged. However, there are impressive grave mounds erected in this era, like in Old Uppsala in Sweden and Borre in Norway.

There are many similiarites between pre-Viking and Viking Age Scandinavians. They lived in tribes where power was linked to individuals rather than institutions and they traded and raided (locally), albeit not on the same scale as the Vikings. During these centuries, Scandinavian ship technology, a key feature of their later raids, developed further.

So, I can answer some of this but only the stoneage in southern scandinavia and the origin of scandivians.

The first evidens we have of people on scandinavia can be dated till about 13.000 BCE, where the first reindeerhunters first began to hunt on the southern steppes of Denmark after the ice melted. The hunters came from germany and has been named the hamburgculture. The paleolitchic period in Southern Scandinavia started 13.000 and ended around 9.000 BCE where the mesolitchic period began. In the Paleolithic the people lived by hunting mostly reindeer, but some clima changes during the allerøds fase (12.000-11.000 BCE) allowed other species as elk and megaloceros to be hunted in these regions as the flora of the land became more diverse.

Other cultures as feddermesser (12.200-11.000 BCE), Brommeculture (11.000-10.500 BCE) and arhensburgculture (10.500-9.000 BCE) also has it place in the southern scandinavia paleolitchic. (The cultures are devided by their tools and techniques throughout the stoneage) We don't know much about these cultures as we lack remaining artifacts, but typology shows different crafting techniques and we also lack bow and arrow evidens from the Hamburg culture, but the feddermessergroup is know to have used bow and arrows.

(Also the "Brommeproblem" is a debated topic in this period, which my professor Felix is researching - tl;dr laacher see euroption around 11.000 BCE might have coursed a step back in the technological advance in this region as it could have cut of the contact with the cultures south of northern germany)

After 9.000 the mesolithic starts (Ends 4.000 BCE) simutaneously as the last glacial period ended (But it's apperently not therefore we go into the mesolitchic but because we began to created axes here - This is something all my fellow students finds wierd, but more trees means new tools afterall.. but whatever) In this period the flora began to take a hold of the landscapes, forrests began to appear and the people living there is now hunter-gatheres - living of hunting, but also effectes by seasonal gathering and seasonal occupation. We have evidens of travel by sea in the beginning of this period, multible paddles have been found (oldest boat in this part of europe i believe is a cano from Pesse, netherlands dated till 7.750 BCE)

The oldest skeliton in Scandinavia is from this period aswell and dates 8.000 BCE and is named Koelbjergkvinden (the koelbjerg woman - scientist has recently found out it acturally is a man).

During the mesolithic period the forrest gets more dens and we begin to live more and more of the sea. This is due to the rising levels of the sea which is increasing rapidly around 7.000 BCE (See "Doggerland" for a illustrations of the prehistoric landscape of northern Europe). By the end of this period we are almost excludingly living of the sea, some even debate if its because the forrest is to thick or if it's just simply because its an abounded foodresource, but the fishing techniques are developing alot during the kongemoseculture and ertebølleculture. (By analysing C13, it's possible to determine how much an individual has lived by marine animals or terrestial animals)
Cultures in this period; Maglemose (9.000-6.400) Kongemose (6.400-5.400) and Ertebølle (5.400-4.000)

Neolithic!! We become farmers! So around 3.700 the southern part of Scandianvia is completely revolutionised and we are now farmers! Its a bit of a mystery why we didn't adopt farming earlier as just south of the current border from denmark, the LBK culture had allready adopted it a 1.000 years earlier, but scientist believe it might not have been necessary to adopt farming as the resources is presumed to have covered more than enough to withstand the population. We also begin to see megaliths graves around the country, which is a phenomenon seen in western europe earlier (up around 300 years earlier in england, france, even northern spain). (The world is widely interacting with eachother, probably more than we expect!)

That's it! There might be countless spelling errors, but my computer isn't set for english I apologize.. It's only the stone age, and it's quite hard to find the specific topic as it's quite huge and books have been written about this, though I've mostly read papers and ofc. also most of the source is from lectures as I study this particularly subject (BA/Prehistoric sourthern scandinavia), but if you have any questions you're more than welcome to ask..