Even if you get darker from living near the Equator, that darker skin is not going to be included in you DNA and passed on to your kids. If it were allclimate, every black person born in America wouldn't be black anymore, their skin would change depending on where they lived.
The same goes for Christianity. I'm a Christian and that's exactly how I see God. He gives us the ability to make our own decisions but He alreadyknows what they're going to be.