>  Nonetheless, the Apache men were described by the writer as being
> wirey -and well muscled, as they stood in the snow absolutely naked without
> appearing to be cold.

A couple (few?) years ago there was a documentary about tracing mitochondiral DNA from Africa to North America. Along the way the host and crew met up with some sheep/goat herders in Siberia. During winter. In blizzard conditions.. 

While the host and crew all had heavy parkas and mittens on - and appreared to be freezing their butts off  - the "natives" wore lighweight sweaters and nothing on their hands. It was explained that the herders' had adapted to their environment by doubling (or even tripling) the number of capillaries in their hands/arms. Better bloodflow, more transferred internal heat.