The Finnish government has spent most of the last weeks squabbling about a topic that is obscure even in Finland – Sámi issues. Most Finns, of course, know about the Sámi, ‘EU’s only indigenous nation’. When it comes to the actual political affairs concerning Sámi, however, the common Finnish reaction is akin “I’m not touching that with a 3.048-meter pole”. I don’t know much about the topic, either, not having grown up in Lapland. This obviously needs fixing. I’ve tried to learn more about it by reading a fair bit of stuff concerning the topic. So, here’s an overview.
I'm not sure where you got the 3500 years-ago figure, but as an estimate of when (Proto-)Saami-speaking people first arrived at where they're currently living, it's probably quite a bit too early according to the most recent well-argued positions. See, in particular:
A lot this early population history is still quite unclear, but more genetic evidence may still come up. Obviously, it might also complicate the picture — as it actually has already with the perplexingly old Uralic/Saami-*looking* findings near the Kola peninsula (Bolshoy Oleni Ostrov), which don't fit the story of the origins of the languages but might be relevant for the speculation around the evidence for Saami assimilation of pre-existing people in the North...
Anyway, I briefly tried to delve into this issue some years ago, as well. I've forgotten a lot, but I do recall that the claim that more large-scale reindeer-herding is a relatively recent introduction in a lot of Finnish Lapland sounded quite convincing. And indeed I think there was some Norwegian (or Finnish?) border control related reason for a lot of reindeer-herding Northern Saamis to move their herds here on a more permanent basis around the 1800s or so. Hard to convince with such poor recollection, though...
As for the Saami groups in Lapland with deeper historical roots within our borders, it's AFAIK established that they relied on a more diverse ways of sustaining themselves not really on reindeer much at all but from hunting, trapping, fishing and gathering to some occasional slash-and-burn agriculture. But it also became clear that these populations assimilated long ago already (as has possibly happened to a much wider extent within more than a thousand years already as the Finns slowly migrated north and east from around current South-Western Finland), meaning adopting the Finnish language and agriculture-heavier lifestyle, and then probably intermarrying to an ever-larger extent. The fundamental reason would have been basically the innate difference between the maximum population density allowed by the respective lifestyles: hunting etc. requires much more territory which slowly got occupied and outcompeted by more Finns per km2, and so on...
I'm not sure where you got the 3500 years-ago figure, but as an estimate of when (Proto-)Saami-speaking people first arrived at where they're currently living, it's probably quite a bit too early according to the most recent well-argued positions. See, in particular:
An essay on Saami ethnolinguistic prehistory
LSS Ánte - A linguistic map of prehistoric Northern Europe, 2012. Available at: https://www.academia.edu/download/46465125/An_Essay_on_Saami_Ethnolinguistic_Prehistory.pdf
Very interesting stuff on many fronts.
A lot this early population history is still quite unclear, but more genetic evidence may still come up. Obviously, it might also complicate the picture — as it actually has already with the perplexingly old Uralic/Saami-*looking* findings near the Kola peninsula (Bolshoy Oleni Ostrov), which don't fit the story of the origins of the languages but might be relevant for the speculation around the evidence for Saami assimilation of pre-existing people in the North...
Anyway, I briefly tried to delve into this issue some years ago, as well. I've forgotten a lot, but I do recall that the claim that more large-scale reindeer-herding is a relatively recent introduction in a lot of Finnish Lapland sounded quite convincing. And indeed I think there was some Norwegian (or Finnish?) border control related reason for a lot of reindeer-herding Northern Saamis to move their herds here on a more permanent basis around the 1800s or so. Hard to convince with such poor recollection, though...
As for the Saami groups in Lapland with deeper historical roots within our borders, it's AFAIK established that they relied on a more diverse ways of sustaining themselves not really on reindeer much at all but from hunting, trapping, fishing and gathering to some occasional slash-and-burn agriculture. But it also became clear that these populations assimilated long ago already (as has possibly happened to a much wider extent within more than a thousand years already as the Finns slowly migrated north and east from around current South-Western Finland), meaning adopting the Finnish language and agriculture-heavier lifestyle, and then probably intermarrying to an ever-larger extent. The fundamental reason would have been basically the innate difference between the maximum population density allowed by the respective lifestyles: hunting etc. requires much more territory which slowly got occupied and outcompeted by more Finns per km2, and so on...