Evolutionary traits generally change slower than the environment. Therefore, the traits that were once helpful can now be harmful because the environment is different. When this is the case, we talk of evolutionary mismatch.
While evolutionary mismatch can and does happen in animals and plants, humans are a prime example because our environment changes so rapidly.
It is important to understand that we essentially have a hunter-gatherer brain and body in a modern society, so there is huge (and rapidly increasing) mismatch. Obesity, most health issues, most mental health issues, addiction, lack of meaning, loneliness... many negative matters of the body or brain can be due to evolutionary mismatch.
This is not to say that everything was perfect when we lived in huts and that everything is wrong now, but that we evolved in the former environment and therefore it is only logical that issues emerge when we live in environments we didn't evolve to live in. That's the idea behind evolutionary mismatch.
So if you have issues, that's not necessarily your fault. It's like blaming a penguin for not thriving in a desert.
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