Ok. So, I love these books, but I'm having a LOT of trouble picturing the characters, and it was made worse by reading the canon physical descriptions. It all started with Cinder. She was adopted, and Lunar,so i assumed she was a different race than her family, Caucasian. The REASON i assumed this was genetics. I can't find a timeline showing exactly how many years Lunars have been around, but, it stands to reason, if they've been around long enough to have evolved their skills, then they've been around to of evolved coloring specific to their race, and i assumed white because they spend their time under domes, so they would have no need for extra melanin to protect them from the suns rays. But then I started wondering, if they got enough radiation exposure to of mutated their DNA, then maybe they did need the melanin, and Cinder had dark skin. So i looked up the physical characteristics of the characters, and discovered that Cinder was mixed race and you don't know exactly what she is mixed with but the assumption is Caucasian and Asian. Channery is described as tan with dark hair, levana doesn't really have a description beyond get glamour so i would say we can ignore her description, and Snow is described as African/Indian, her father is african her mother is Indian. So that means there are at least four races on the moon, an African race, an Asian race, an Indian race and a Caucasians race, but ethnically, they are all Lunar. I know it doesn't really matter, but that just doesn't make any sense to me. The number of people are small compared to the earth. The lunar gift is described as having started only in the royal family, but a time went on and people started having affairs, the gene spread through the population, which makes it clear that the different races weren't kept apart. So how, after enough time for a gene mutation to of passed around the entire population, on a world where the only people breeding are from the same group, (no earthlings are being brought in for genetic diversity) could there be four races? Wouldn't they have become one race eventually, especially since they are their own ethnicity. And even if the argument was made that african and Indian and Caucasian descent was being used to help us to picture the different shades of coloring their race could be, why would Cinder be described as mixed race? It just seems like a big over site when so much attention to detail has been put into the rest of the history and description of Luna and how they came to be, one of the first things most sci-fi stories do is assign specific characteristics to a group from a specific planet/moon, especially one that's isolated and cut off from beings from other planets/moons moving there and having relationships. Does anyone know how Luna could be so isolated for so long but manage to keep specific races while everyone lives in the same atmospheric conditions? Wouldn't one of the few GOOD things about the Luna society be, by this point, at least race no longer exist? Is there something I've missed?
We never know for sure how many races there are. You said it yourself - "The number of people are small compared to the earth." so of course we expect a little bit less of diversity, however they still have human DNA. We only got a little bit of insight on the Lunar royal bloodline throughout the series, but we've never covered Luna as a whole. Perhaps all races exist on Luna, and perhaps they don't.
It said in the series that the Lunars were just normal people who went to live on the moon sort of as an experiment. There were probably multiple races of scientists participating in the experiment, so when they had kids, those kids had kids and THOSE kids had kids and so on. Their magic is just science from their experiment, too.