Evolutionary theory contends that genetic is necessary and beneficial for humanity when there is an environmental change.

variation

Explanation:

Genetic variation is what makes us all unique as a result of subtle changes in our DNA.  The Theory of Evolution is a process in which organisms change over time as a result of adapting to their environment.  Charles Darwin came up with the term Survival of the fittest, in any environment plants and animals from the same species show natural variation in their physical characteristics, like neck lengths in giraffes.  Darwin suggested that the plants and animals best suited to the environment will survive and pass on their characteristics to their offspring. Over time, the characteristics of the surviving members of the species will become predominant.

Example: Peppered moth

In London in the 1800's, 98% of peppered moths had light colored bodies and only 2% were dark.  The light moths were the same color as the trees so they could easily hide from hungry birds and not get eaten.  The dark moths however were easy to see and were eaten.  Then came the factories and smoke of the industrial evolution and many trees turned black with soot and suddenly the dark moths were able to survive better as they now looked like the trees and the light colored moths were easier to spot and eat.  By 1895 the dark peppered moths made up 95% of the population and the light colored moths only 5%.  This is an example of natural selection, because of the gene that makes the moths dark, it allowed them to flourish when the environment changed, they adapted, reproduced and survived.

The change is not a physical change because a new chemical is formed on the outside of the statue.