Re: What is the purpose/function of finger/toe nails & hair ?

Well part of your question is correct.  Behaviors and structures in living 
organisms are usually present because it gives that organism some adaptation 
to help it survive in the environment.  But, there are some things called 
vestigial structures.  These are structures that are the remnants of 
structures that were once useful to the organism (or one of its evolutionary 
ancestors), but are no longer necessary.   

One of the characteristics of primates is that they have nails rather than 
claws.  I think this has something to do with how primates climb.  If you 
look at other mammals that climb, like squirrels and cats, they use sharp 
claws to dig into the surface of the tree or rock they are climbing in order 
to gain traction.  However, primates, such as monkeys, use their nimble 
hands and fingers to grab onto the trees and rocks that they are climbing.  
Long, sharp claws would just get in the way.  Our finger nails are vestigial 
organs left over from our primate ancestors.  

As far as our hair goes, the little hair that is left on our bodies still 
has it's uses.  For one thing, the hair on our head still keeps our heads 
warm (remember most of your body heat is lost through your head).  Also, 
when it is hot outside, it keeps the sweat from running down into our eyes.  
The eyebrows also help with this.  We also can't forget the social side of 
hair.  Not all organs/behaviors are retained simply because they make us run 
fast or or get more food.  Some sturctures/behaviors exist so we can get 
mates and produce more offspring, this is the most important aspect of 
evolution.  The hair on our heads may be retained simply because we find it 
attractive.  Ask yourself, how many naturally bald women/men are considered 
beautiful/handsome?  I can't think of a single one.  Actually, polls have 
shown that about 65% of men prefer women with long hair.  Also, men worry 
constantly about going bald, because it makes them look old and 
unattractive.  These sound like a good evolutionary reasons for people to 
have hair.