This is entirely down to your parents – or more specifically, the genes you inherited from your parents. Curly hair is an autosomal dominant trait. That means if one of your parents gives you a curly-haired gene but the other gives you a straight-haired gene, the ‘stronger’ curly-haired gene wins the day and expresses its trait. However, it’s not always quite so clear cut, and depending on the type and strength of the genes, you can end up with something in between, such as wavy hair. Other examples of autosomal dominance include brown over blue eyes, freckles over no freckles, and dark over blonde hair.
With approximately 100,000 hairs on the human head, it’s a busy area of growth. Hair starts growing in follicles that are located in the dermal layer of the skin. Flattened hair follicles lead to thinner hair strands that naturally curl. Rounder hair follicles lead to tubular strands of hair that are harder to curl, and so grow straight. Of course, some people with straight hair want curly hair, and vice versa. Straightening or curling hair is a way to overcome genetics, but it won’t last very long as the hair will continue to grow in its natural way.
Answered by Aneel Bhangu.