Mismatch theory

Mismatch theory is a concept in evolutionary biology that refers to fluidity in fitness criteria.

The essence of mismatch theory is that organisms possess traits (including behavioral, emotional, and biological) that have been passed down through generations, preserved by natural selection because of their adaptive function in a given environment. However, the given environment of the evolutionary period can be quite unlike the current environment. Therefore, traits that were at one time adaptive in a certain environment, are now "mismatched" to the environment that the trait is currently present in.