I know that hair was used in the Greek and Roman times as sling material. Blonde hair was supposed to be best. ( Siguy, you and you brother better look out)
  Hair does respond to temp and humidity, but it is of little consequence.

I had plenty of horse hair braided slings that i brought through ebay a while back and I traded them on the site with other members.  They work great!

Here is a link:

http://www.slinging.org/forum2/yabb/YaBB.cgi?board=trade;action=display;num=1144...

I have traded them all away though.  It turns out my family is allergic to horse hair.

I think human hair would work even better due to its length and choice of colour!  I personally prefer red hair.

Also, for torsion catapults, ( onanger and others) hair was used for the rope that powered the thing. I have this image of all these bald people around, though.
  As anyone who has done weaving and ropemaking knows, you need a alot of the material to make it work. I can't imagine how much hair would have been required to do the job.

Bigkahuna,

The funny thing is I DO have Mongol blood in me!   My grandma from my mother's side is half mongolian.  Is must be from my dad's genes that we are allergic.

Monty Python material indeed .

Big cloud of dust off in the distance getting closer. Fleeing townspeople wheeling carts full of their belongings and pulling donkies and cattle along. Children crying and people running everywhere screaming " THE MONGOLS ARE COMING, THE MONGOLS ARE COMING". The dust cloud grows closer and you hear the thunder of many horses. The dust cloud grows nearer and finally comes to a stop at the edge of the village. It takes several minutes for the dust cloud to clear and when it does we see hundreds of Mongol Warriors in full battle array on foot banging coconut shells together, the minions of the dreaded Lo Family, who because of an allergy to horse hair can't ride horses but simulate the sound with coconut shells which make using their dreaded Mongolian bows very difficult.

I can't get on ,I'm at work!!!

Coconuts?  Nah ask any invading mongel with a horse hair allergy whether he would prefer coconut halves or a shaved horse and the horse gets cold every time.  That's how they got round the great wall, people fled before the sneezing as they were afraid of catching it.
As to hair slings I haven't made one yet but have been saving up my own combings,  it's been a few months but I think I may have enough for a very simple split sling, not even a braided one just like two strings,  but am waiting untill I have more cordage skill as it takes so long to collect.  I twisted a litttle of it up and it is really strong, something the thickness of the jute garden twine would cut your finger open before it broke.  I have read somewhere ( sorry can't remember the source ) that human hair has the same tensile strength of aluminimum.

I'm a novice on the craft side of things so if anyone has a suggestion for a material I can practice on before using the slow to replace stuff I'd be grateful, horse hair is much thicker.

It's not that slow though, you'd be amazed how much falls out each day when you save it up.  I'm only keeping the stuff from the hair brush but if I could work out a way of cleaning the stuff from the vacume cleaners brush I could probably get as much again.  My own hair is medium long and my guess is I could make a braided sling a year   Quite like the idea of slinging with something made totally from my own body, ok so I'm weird, but with the help of friends and familly collecting wouldn't take long at all.    Some of the ancients thought it the best material of the lot.  Worth doing and can't complain about the price.