I would imagine, if there were mutations that allowed for control of those things, it would ultimately be a disadvantage for survivability and result in being selected against. Generally, you would not want to turn off pain response.
I’m not sure conscious control of your immune system would allow you to respond better. For however that would even possibly work, I’m sure it would be prone to doing a much worse job, especially for an infant, that doesn’t know how to control such a thing. It would also require a level of intelligence, and understanding, making it something that really couldn’t manifest until we get to higher cognitive species and at that point, nature has developed an optimal auto response that would provide an advantage over something that would potentially kill when mismanaged.
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