The old debate of nature vs nurture continues to rage on today. While the pendulum has swung back and forth between the two, there are studies that show strong correlations of personality traits within families. However, it is not a 100% correlation, so that leaves open the question: Is personality inherited, the product of environment or simply chance? There are difficulties with any one of these arguments.
Consider the evidence in favor of heredity. This evidence usually comes from studies involving identical twins who were raised in separate households. This is not a common scenario, however, and that makes it more difficult to study and interpret the data. Scientists studying these twins have to isolate the factors that caused the separation to begin with. In addition, there are so many genetic and environmental factors that can influence behavior that determining which caused a specific effect might be open to dispute as well.
Yet, the influence of genetics is still undeniable. According to the article “Genetics and Behavior” on the online Encyclopedia of Human Diseases and Conditions, in 46% of twins where one has schizophrenia the other also exhibits symptoms. The same article points out that 40% of the factors that influence obesity are genetic. It is obvious that genetics play a role.
However, it should be noted that the inverse means that in 54% of the cases where one twin has schizophrenia the other twin does not. Likewise, 60% of the factors causing obesity are environmental. This suggests that environment still plays the larger role in shaping the individual's personality.
It once was common for people to speak or write about how their destinies were shaped by Divine Providence. This was a realization that many things were outside of a person's control. In the case of environment, no one chose the family they grew up in, what parenting philosophy their mothers and fathers would use to raise them, what sort of meals they would be fed or even what part of the world they would grow up in. Likewise, neither did anyone choose their heritage, eye color or what diseases they would be genetically disposed to. None of these things were chosen, and neither could parents choose the genes they would pass on to their offspring. Therefore, it was generally believed that Providence determined these things.
If someone doesn't believe in Providence, however, then they usually believe it was chance that everything came to be the way it is. It is still a mechanism that provides different outcomes even in very similar circumstances. It explains why almost half of the sets of twins with schizophrenia have both exhibiting symptoms while the other half do not.
So, call it the hand of Providence or call it chance, life still has great variability and is full of surprises. It is this unpredictability that allows us to survive as a species. It is also what reminds us that everyone is as individual as a snowflake and a unique individual.