Apparently populations can adapt genetically to some seriously changed conditions fairly rapidly ~ doesn't take 100,000 years to adapt you to 45 days of starlit skies ~ or to keep you from dying just because you were trapped in a glacial creek, underwater, for 6 hours!
The night vision thing isn't remarked on all that much by any of the folks who've done medical surveys of the Sa'ami, but they did find that some tribes have an 18% incidence of dental dysplasia of 3 or more teeth ~ that's a missing or twisted tooth BTW. In this case they're born with the tendency. Also, the Skolt Sa'ami, down to a mere 5,000 people in Europe, find the odor of mutton nauseating ~ still trying to figure that one out, but that's fur shur genetic!
They have a very high incidence of blondism with a low incidence of lactose tolerance ~ reindeer milk is so thick with cream it isn't drinkable anyway ~ so they make cheese out of it ($125 per pound currently), plus there's the possibility they can both ski and skate naturally without any training at all ~ the programming is built in!
Wouldn't be eating any wheat, barley or rye either, and best to visit the doctor when you have runaway atrial arrhythmia ~ something that has some usefulness in the far North but it can kill at these latitudes. Read up on Atrial Fibrillation now just in case you need to know about it.
Polarized glasses help!
They vary in severity ~ one of them is a minor irritant ~ and may accompany hereditary atrial fibrilation. The second is more severe but can be controlled relatively easy. The third sometimes leaves its victims in a psychotic state ~ all three are gene controlled.
Typically the victim's urine is photosensitive and will turn purple in sunlight due to the high incidence of heme their kidneys excrete.
Life in the arctic is different. The animals have a very high incidence of iron compounds in their flesh. The landscape has enormous expanses of exposed iron ore. Excess iron may be removed from the body's systems simply by excreting heme molecules twisted one way rather than another. Another condition involves loss of Vitamin B12 ~ in the far North folks eat a carnivorous diet so that loss is not a problem. However, in the lush latitudes in the South it's serious, and enough loss of B12 makes you act crazy! That's what the B12 sublingual pills are for ~ they used to give folks shots for this. If anybody reading this has a blood relative using B12, they probably ought to ask the doctor to check their own levels, and if low, fill up the tank!
I keep my eyes open for intermittent porphyria being related to bizarre acts but so far I haven't seen any ~ but since most cases are in Scandinavia, the authorities probably keep them quiet lest the peeps be disturbed.