Darwins contribution to science and to the field of psychology are immense; yet there are still those who oppose to his theories and find it controversial. Darwin’s theory of natural selection was the first rigorous theory to suggest, with evidence, that the various forms of life on Earth today could all, in principle, be traced back to a common ancestor. It was controversial because it obviously directly contradicts the bible, which says that God made all life, exactly as it is today, over the course of just under a week, in 4004 BC.
Darwin wrote that humans and animals were descended from a common ancestor. Darwin stated that humans and animals have a lot in common, the field of comparative psychology (i.e., studying animals to learn about human behavior) increased in popularity. Scientists had studied animals for thousands of years and made inferences about humans from those animals but Darwin’s theories led to researchers making inferences about human behaviors such as learning, memory, emotions, and even social interactions based on observations and experiments with animals.
It changed science because it proved to the community of gentlemen scientists and natural philosophers that the process of collecting evidence, and then developing a theory to explain that evidence, and then testing that theory against new evidence, is a Really Freaking Good Idea, and should be used extensively on everything. And so it was.
These are, his doctrine of the evolution of instinct and the part played by intelligence in the process; the evolution of mind from the lowest animal to the highest man; and the expressions of emotion.
Darwin’s theories also had a large impact on psychology in general; much of psychology today has strong biological underpinnings. This traces back to Darwin. Psychologists often try to explain psychological concepts in light of biological processes. Some schools of psychology are almost strictly Darwinian, such as evolutionary psychology. Even though Darwin was not a psychologist, his theories have had a large and lasting impact on the field of psychology.