David Pearson, of Ilam Primary School, asks :-

Why does hair grow?

David Scobie, a biochemist at the Wool Research Organization of New Zealand, responded.

Animals live in a complex environment and can not make clothes or houses to protect themselves from the weather. Imagine standing outside in the nude. During the day you might get sunburnt and at night you might freeze. A calf or sheep about your size, standing near you would not. Why? Hair helps protect them from the sun and cold. Many animals take this a step further and shed their winter coat for a summer one. Horses have long hair in winter and short in summer. The arctic hare grows a white winter coat to match the snow, and a normal darker coloured coat in summer for when the snow has thawed.

Why don't we grow more hair? Maybe we came from a tropical climate where we wouldn't need it. Perhaps we tamed animals like sheep so long ago that we need their hair to keep us warm, and they need us to shear them. We don't freeze after shaving or going bald, but a sheep might if it is shorn before a bad storm. We still grow hair because our ancestors needed it. Whatever the reason, we don't really need hair because we protect ourselves with clothes, houses, heaters, hats and sunburn cream. However it is handy to have on top of our heads because that means we dont have to worry about putting a hat on except during very cold weather or in mid-summer.