'Typically, children with dark hair will keep their dark hair into adulthood. But some children with light hair, including towhead blonds, strawberry blonds, dishwater blonds and redheads, see their hair go dark brown by their 10th birthday.

The reason for this change is because the amount of eumelanin in your hair increases as you mature, according to some research. But just why eumelanin production ramps up (or why those specific gene expressions change) is not entirely clear.'

- live science may 29th, 2013

https://bit.ly/2kNkNL

H

'Neuromelanin (NM) is a dark insoluble polymer pigment produced in specific populations of catecholaminergic neurons in the brain. Humans have the largest amount of NM, which is present in lesser amounts in other primates, and totally absent in many other species.[13] The biological function remains unknown, although human NM has been shown to efficiently bind transition metals such as iron, as well as other potentially toxic molecules. Therefore, it may play crucial roles in apoptosis and the related Parkinson's disease.[14]'

-https://bit.ly/2kMZ9Hp