actually bob yes what i said IS correct, maybe you should pay more attention because IN the game it is said specifically that the dwemer forced all the enslaved falmer to eat fungi that would make the ones that eat it go blind AND also make the offspring of them go blind. Please try to remember that this is a GAME and that the laws of science that apply to REALITY don't always crossover.
So your suggesting that the fungi they ate altered their genetic material? This couldn't happen.
What could have happened is that all falmer were forced the eat the fungi, but the ones with bad/no eyesight due to a random mutation survived and the ones that had normal eyesight died due to the fungus. But this would need thousands of years for them to evolve blind.
The end of the day, this is a game, who's to say an in game book is correct over logic based on the real world, it's nonsense anyway. Many aspects of the real world are the same in tes.
Where on earth do you get the logic that the ones with eyesight died out because being blind would be better? Blindness is NEVER an advantage. Even underground there are lights emitted from mushrooms. Being blind is not a genetic advantage in any way! Having sight in pitch blackness is better than being blind in pitch blackness because if the darkness ends you still have sight.
"Over the thousands of years that the falmer evolved, to much variation has occurred for them to be classed as the same species." -- If this is true then why can modern caucasoids, mongoloids and negroids interbreed with each other? They are tens of thousands of years apart and they produce fertile offspring.
And it may be possible to pass on acquired afflictions, especially in a fantasy world. In fact, a change in diet for humans and our ancestors changed the way we digest. Example: European descendants are less likely to be lactose intolerant due to early cattle raising and dairy consumption. You say that these changes over thousands of years would change them, yet you only do it for your benefit. Europeans developed the ability to digest dairy products while Africans and Asians didn't, at least not on the same level. Genetic change due to diet, right there.
You're right there are specific examples of distant species with common ancestry producing fertile offspring, but more examples of the inverse, over time too much variation has occurred for them to produce fertile offspring. I gave an example above to how the bad eyesight could have evolved, note that I said 'unlikely' in my above comment. I also said this isn't the same as the real world, so who knows, all we can do is speculate.
Do you not see how these people have evolved? The diet has resulted in people evolving in a specific way over time, but it's not that the food altered their DNA, it's that the ones with mutations for the allele that stops lactose intolerance survived or were superior in passing on their genetic material. This means that some situation occurred in which the snow elves with bad eyesight passed on their genetic material but the ones with better eyesight didn't, likely in a situation where eyesight wasn't necessary to survival.
What you are saying is like saying that Altmers are not High Elves, Bosmers are not Wood Elves, Dunmers are not Dark elves and Dwemers are not dwarves. Snow Elf is a term used by the Imperials to describe Falmers, just like elf is a connotation used by the Imperials to describe the mer races. Snow elves themselves would call them selves 'Falmers' as would any other mer races in the game.
I'm unsure about this because so many people in game describe the snow elves as descendants of the falmer. But I just had a read of the falmer lore uesp page, which supports what you say, so I guess I was wrong.
It's unknown to us whether modern 'falmer' are part of the same species as their descendant 'falmer' though, it's possible that they could breed as described above, but very unlikely. I guess I assumed (based on what I heard ingame) that snow elves were the descendant species of the falmer.