The book, "The Sunburnt Queen"'by Hazel Crampton, is about a 7 year old English girl who washed up on the Wild Coast of South Africa in the 1730's & was adopted by her rescuers. She grew to be a woman of astounding beauty & wisdom, becoming the Great Wife of a prince. So starting a dynasty that extends to many of today’s Xhosa royal families. Because of her recessive gene in the blood line, every now & then, a child in the area is born with bright blue eyes.
According to science, people of the earth began in Africa, and the more people migrated around the world, the more physical changes would develop because of adaptations to certain areas. People who evolved in the same spot for a long time did not change much.