According to Darwin, the driving force behind evolutionary change is

According to Charles Darwin's theory of evolution, the driving force behind evolutionary change is natural selection. Natural selection is the process by which certain traits become more or less common in a population over time, based on their ability to help individuals survive and reproduce in a given environment. Those individuals with advantageous traits are more likely to survive and pass on those traits to their offspring, while those with less advantageous traits are less likely to survive and reproduce. Over time, this can lead to significant changes in the characteristics of a population, ultimately resulting in evolution.