Re: Are fair skin or fat deposits good indicators of ancestral lineage in very cold regions?

In general, one could surmise that paleolithic human skin tone was 
related to sunlight intensity; those individuals who were able to better 
withstand prolonged or intense UV radiation at the equator because of 
denser melanin expression were more likely to successfully procreate, 
etc., etc.  I'm not aware of any research attempting to follow 
the "evolution" of skin tone, however.

The fat storage issue is complex.  Paleolithic humans tended to be a 
nomadic bunch for many reasons, including (but certainly not limited to): 
1) It got really cold in certain areas in the winter (forget Chicago-- 
let's try to imagine why anyone would live in International Falls, 
Minnesota!); 2) Many large mammals (meat sources) went south for the 
winter; and 3) Plant food sources died or were inaccessible during the 
winter.  The fact that humans were generally adaptable to fluctuating 
food resources, understood the seasonal round and its effect on weather 
and food resources, and had some level of clothing to protect themselves 
suggests to me that if it started getting cold wherever they were, they'd 
just pick up and walk south.  It's hard for me to imagine any significant 
portion of what was a very dispersed nomadic human population being 
subject to so much population pressure that they were forced to perish in 
a lethally cold environment.

Once agriculture comes along, of course, we start setting up permanent 
settlements and attempting to store food.  Once this system becomes the 
norm, it would certainly be possible to succumb to the combined effects 
of a food shortage, severe weather, and a lack of body fat.