How long does it take for a normal strand of hair to decompose in natural conditions ?

Answer 1

The DNA within the hair can break down under natural conditions in just a few weeks, that is why when DNA is collected from hair they try to get it from the follicle which is attached to the end of the hair when pulled out of the head. However, the hair itself can last for many decades or longer, especially if preserved in the mud or through other natural preservation actions and fossilization.