system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5: Why do creatures that sit in the baking sun all day, like lizards, not get skin cancers?
gpt
Skin cancer is caused by UV damage to skin cells.  Specifically (and not really ELI5) UV light causes damage to the DNA of the skin cells, which, when un repaired, can cause the cells to replicate uncontrolled and result in cancer.

So, how do you prevent this?  The easiest way is to shield the skin cells from the UV light.  You can do this with sunscreen, a hat, etc.  Or you can produce more pigments in the skin.  Lizards do both.  The scales shade the underlying skin from the UV light, and their skin is full of melanin, a dark pigment that acts to absorb the UV light before it can damage the DNA.