[roenxi]

Well no, being able to breath fire is probably evolutionarily stupid. There is no reason to think it would be helpful, it'd presumably involve animals building up a highly flammable concoction inside their bodies and occasionally exploding. For no gain, since they could do what everyone else does and gather combustible material and set it alight. And flamethrowers just aren't very effective weapons on average since they'd tend to burn an animal's home down or be very energetically demanding for no upside vs something like a good pair of jaws or claws.

If evolution can figure out photosynthesis it can figure out flammability. Flammability is actually pretty easy. Even monkeys can manage it. There probably have been animals that breath fire and it just didn't catch on because it is wholly impractical.

[jjk166]

Substitute any other adaptation that provides benefit but for which the necessary combination of mutations is unlikely to occur.