It happens in EA because the researchers don't account for over fitting. The experimenters often do not validate so the population converges to the training set

It happens in EA because the researchers don't account for over fitting. The experimenters often do not validate so the population converges to the training set maxima too far. If you had 2 simulations of walking. You would select and mutate based on one sim and stop the evolution when performance degraded on the second sim. Not blindly maximize the one measure. if validation were performed the population would not evolve into the cracks of unlikely physics loop holes.