A friend of mine went to Montana for graduate studies in linguistics - she's studying to be a speech pathologist - and was apparently in a conversation with someone down there about Yup'ik. She'd told him that Yup'ik has an incredibly elaborate set of demonstratives (ways of saying "This" or "That"), and when she told him that there were 30+ demonstratives, he refused to believe her. :p
But it's true! There are over 30 demonstratives in Yup'ik, not counting all the positional words. Why so many? Well, I got told this explanation about how the tundra is confusing to navigate on, and so the system gets elaborated to work out where things are. I'm not sure if I believe that - I think it's more likely that it's complicated because it's complicated. English has a very complicated and irregular system of plurals, like Goose-Geese, Cow-Cattle, Moose-Moose, Dog-Dogs, and so on. Over time, we lose a lot of the complication in English (the irregular forms are purged), and the same is true with Yup'ik - people use a smaller selection of demonstratives than before. But no one would argue that in English's primordial environment, people had to be very good at quantifying animals. It's just a silly argument.
In grammar person talk, Yugcetun demonstratives can be either 'extended,' 'restricted,' or 'obscured'. That is, they can refer to something at one spot, not moving (restricted), something spread out or moving (extended) or something we can only infer is there (obscured). For example, we have man'a, which is by me (the speaker) in the spread out sort of way. Or unegna, which would translate so elegantly as "that downriver one that is spread out." Pamna would be "that one upslope that you can't see." The translations don't really roll off the tongue in English!
In a simple sentence, I could say "Kan'a Angsaq cukaituq." Which would be "That boat (down below) is slow." With nouns you use them pretty normally, except the plurals get funny. If I wanted to say boats, I'd say Kankut angsat cukaitut... so instead of just changing the ending like most words (Kavirliq->kavirlit) you have to strip it down, add on a -ku- and then you get to end it. Adverbs are even more different.
I've wondered if inupiaq has a similar system of demonstratives, or if it's different. The languages borrow a lot of vocab from each-other, but I'm told the grammar of inupiaq is different in ways. If someone knows, I'd be very curious to hear.
Here's a really cool shirt my friend made for yup'ik demonstratives. He gave me one, and I've worn it around town! :)