> I specifically outlined strong selective pressures in the environments

No, you didn't, because humans behave quite differently to your average animal. The only strong selective pressure you described was climactic: everything else can be mitigated with straightforward tool use. (And heck, going "oh, our skin is getting sunburned, let's be nocturnal instead" might cause your A-islanders to develop paler skin.)

You seem to be confusing "observed data in the real world" and "things that seem obviously true". If you pit your "obviously true" against other people's "obviously true" in your own head, of course your own "obviously true" is going to be the victor.