For the first time the mention of Finland (Fenni) appeared at Tacitus in his essay Germania (98 year). The author, guided only by stories, describes the inhabitants of this country as primitive savages who know neither weapons, nor horses, nor dwellings, but feed on herbs, dress in animal skins, sleep on the ground. Their only weapons are spears, which they, not knowing the gland, make from bone. Tacitus distinguishes between Finns and Sami (Lappen), a neighboring people who lived on the same territory and apparently had a similar way of life.
At the dawn of our era, a vast region, which began to be called Finland only in the 15th century, was not yet a state or cultural whole. In the first 400 years AD., with the beginning of the development of agriculture, the region could feed only a few tens of thousands of people, as the climate and nature were harsh, and new ways of production came from the early agricultural societies of the Mediterranean slowly and with difficulty.
From V to IX century AD. The population of the coastal areas of the Baltic region has grown rapidly. With the spread of cattle breeding and farming, the stratification of society intensified, and the class of leaders began to stand out.
Up to the 8th century, the settled population was concentrated mainly on the southwestern coast, as well as in the fertile areas along the Kumo River and its lake system in Satakunta and Häme. In other parts of the region, there was a rare nomadic population — the Sami who migrated over large territories and engaged in hunting and fishing.
In the middle of the VIII century, the first significant stage of the settlement of the region and the spread of culture began. This was facilitated by the relative warming of the climate in Northern Europe, along with innovations in the field of agriculture. Residents of the southwestern coast and the Häme region, who practiced in particular slash-and-burn farming, began to gradually settle to the northeast up to the northern shores of Lake Ladoga. The settlement of the southern shores of Ladoga by Slavic tribes began gradually.
Since about 500 years, the Aland Islands are settled by North Germanic tribes. In the Viking Age of 800–1000, the Swedish Vikings began to set up trade outlets and colonial settlements on the southern coast of Finland. From then on, the Swedish element began to be introduced into Finnish society. However, in terms of mutual assimilation in the sense of language and customs, it was difficult to speak at that time due to the lack of a common residence area, since the Swedes settled on the coast, and the Finnish tribes lived in the forests. At the end of the Viking Age between state formations on the Baltic Sea, a competition begins in the colonization of Finnish lands, whose population was in paganism. At the same time, this was the era of Christianization, both in favor of the Catholic and Orthodox churches.
Sources:
Essays on the history of Finland from ancient times to the beginning of the 20th century
Brief history of Finland
The history of the Finnish people
Historiallinen Arkisto (“Historical Archive”) // Periodicals of the Finnish Historical Society.