Does darker skin color make it easier to live under sun?
It isn't about heat but ultraviolet light. Melanin is the pigment that makes our skin colour whatever it is and in darker skin there's more melanin. Melanin dissipates UV, which otherwise would cause skin cancer as it introduces mutations into DNA. Melanin production is stimulated by UV so that's why tanning beds work, our body senses the danger and responds by making our skin darker. Yes this makes us hotter but that's a small price to pay, melanin needs to be dark to do its job well.