Redheaded people are seen quite frequently in North American commercials, tv shows and movies despite the fact they only represent about 1 percent of the population. There are higher percentages in areas like Ireland and Scotland, and one would not expect to see any in regions like Africa, Asia, or South America. I was distracted one time when I met a woman with red hair in Ukraine. It wasn't that I was attracted to her more than any woman, but my mind raced to why she might possess that genetic type.
Red hair, like blue eyes, is carried by a recessive gene. This means that it requires both parents possessing that gene to have children to display the characteristic. When you have a closed-in population, it leads to a high level of inbreeding. I am not saying in present-day societies, parents and siblings are committing incest. My family has been in this area for over 150 years. When I had step-children, I had a very unfunny joke that I was more related to them than their father. He only had a single connection to them. I was connected from five different lines. I was distantly related to each of them through both parents. None of those connections were closer than third cousins. One way to complicate things genetically is when a brother and sister marry a brother and sister, and then generations later, their descendants marry.
Sadly sometimes recessive genes are deleterious. Recently the son of a cousin and his wife lost a child due to a genetic illness. Neither one came from this area; they had been born almost a continent apart. The gene does not run in our family, so my cousin might have picked it up from her father, or it might have been passed to her son from his father. The factor that made them both from closed-in populations was religion. This particular illness frequently happens in families descended from Irish Roman Catholics. Any time that you have populations isolated from others you will start to see recessive genes become reinforced. This isolation could be caused by obvious ones like geographic, and less obvious ones like social (royal families do a lot of inbreeding), social (groups like the Amish who isolate themselves from others), and religion.
The Vikings were most likely the source of red hair in the area of the British Isles. Did the woman in Ukraine receive her red hair from the Vikings or had that gene passed through Ukraine to make its way to the north. It would be interesting to find out if the mitochondrial DNA of the Paracas skulls is similar to red-headed women in Ireland. It is possible that the particular gene or set of genes are susceptible to a mutation in inbreeding.
That is why I am not so concerned about the deformations found in the Paracas skulls. Doubtless, the Paracas were an inbred population but the only question might be is the skull shape an issue of mutation, or some recessive gene stemming from some forgotten Neandertal-like ancestors.