From the ancient greeks to more recent times, scientists saw the brain as a "blank slate," meaning that it is completely blank at birth and anything can be written onto it. however, as studies of genetics and evolution expanded throughout the twentieth century, scientists found more evidence that many of our behaviors and thoughts are determined by genetics long before a child is born. therefore, the understanding of human thinking has moved away from the "blank slate" because the explanation that thoughts and behaviors are a mix of what humans are born with and what humans learn better fits experimental results and observations. the decline of scientists' acceptance of the "blank slate" idea is an example of how a(n) can change to better fit evidence.