Guanches in the Canary Islands

Not really a linguistic question but one that I hope is of interest.
When the Spanish conquered the Canary islands in the 15th century
they described the population of the islands, the so called Guanches,
as being tall,often fair haired and blue eyed. Their society was what
we would call neolithic and they apparently had no seafaring skills.
Their origin is wreathed in mystery. Amongst the suggestions that
I've come across is that they were descendents of Cro-Magnon man,
(surely not), that they were related to the Berbers of North Africa,
descendents of some Ibero-Celtic people,(unlikely?),and even that
some Nordic tribe settled there,(the most unlikely of all, given the
lack of navigational skills?). I'm told that the name Guanche comes
from their native language and means 'man'. Does anyone know any more
about their language and does it give a clue as to their origin?
Finally, and I hope this isn't a daft question, could there be some
environmental factor to explain their 'fair' appearance; for instance
dietaty or chemical?
I'm fascinated by this enigma, and hope someone can throw some light
on it.
Thank you
David James