When I saw this thread get bumped I briefly read through it again in preparation of continuing the discussion, but alas, nothing new has been added. However, I did notice something that I'd passed over last time. It got me thinking a bit and I'd like to touch on it. Namely, this:
It is recorded in La Verendrye's journal (1730's) that his party came upon a tribe of "white Indians" that were 7 feet tall, living in southern Manitoba.
When other tribes were asked about these white Indians, they couldn't answer anything about them as they had no idea where they came from.
This interests me. A tribe of possible Europeans that are reportedly seven feet tall? My first thought is that this is an exaggeration, but let's assume that it's correct and dig into it. If they were indeed 7 feet tall, this implies that they could actually grow that tall in the first place. Modern medicine tells us that average height is determined by genetics and diet. Archaeology tells us that modern humans are the tallest that they've ever been, on average, almost certainly because of our diet. It would stand to reason that there's a population somewhere in Europe where the average height is around 7 feet, right? But there isn't. So why not?
I can explain this one away. There's been a lot of genetic mixing and matching over the last 1000 years. Civilations conquered and were conquered, foreign armies occasionally swept through, people moved around for various reasons, etc. The "genetically average" man living in central Europe today would be similar to his equivalent in 1000 AD, but probably not quite the same. It's possible that there was a group of 7 foot tall people somewhere, but they've simply been bred out over the centuries. I can accept that.
When Iceland comes into the picture though, I can no longer accept that. That is a very special case, and the citizens there have received some attention because of it. Here's an example:
https://www.wired.com/2015/03/iceland-worlds-greatest-genetic-laboratory/ In Iceland, we have a country that's been geographically secluded from the rest of the world and was never conquered, or even attacked for that matter. Most people until fairly recently likely didn't even know that it was there. There was very, very little immigration to Iceland, as there was very, very little reason for anyone to go there. The population today is primarily descended from a small number of original settlers. As a result of this, the "genetically average" Icelander is quite similar to an Icelander of 1000 years ago; if anything, Icelanders today are taller, as they're not constantly dealing with famines and malnutrition like their ancestors were. A quick Google shows that the average height for Icelandic males is 5'11 1/2" - a bit taller than Americans, but interestingly enough, right in line with Norwegian males, and also Swedes and Danes.
So maybe there wasn't as much mixing back in Scandinavia as I'd thought. Regardless, no population today is anywhere near that tall. I have no reason to believe that people were any taller back then on average.