Responses
It's common for those with Native American blood to become more tan during the warmer months and lighter during the colder months. They can get quite dark during the summer months. People with Native American ancestry are common where I live and I'm one of them. Most of us are not legally acknowledged.

It makes sense for the men to be darker than the women. Men stay out in the sun, women probably spend time doing stuff by the shade sure the jump of colors is weird but I know people who can have that jump of color difference in the summer. Not a lot of people change like that but I can see it if your whole lively hood is spent at sea or at the sun