system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why do people with dark skin have lighter skin on their palms and the soles of their feet; and yet not in other places devoid of sunlight: scalp, armpits etc.?
gpt
The difference is not due to sunlight, but skin thickness. The skin on your palms and feet is fundamentally different than the rest of your body, because we use these surfaces to perform numerous physical tasks. So the skin there is full of extra protein called "keratin" that makes it much thicker and durable. It also makes the skin appear much lighter.