While most Native Americans could explain where the ginger gene might have come from, there was one exception - a Cherokee girl called Lakia - whose family knew of no European ancestry.

"It is a totally different colour of red," Kieran said.

"It's deep ruby. That really intrigued me."

In the book, Lakia says that all her family, on both sides, have jet-black straight hair but hers turned red during her childhood.

"Everyone thought, since I was about eight, that I dyed my hair," she said.

"And still now everyone's like, 'what hair colour is that?'."