Sir Frances Galton was not only related to Darwin he also did very similar research to Darwin. His most important contribution to modern psychology likely was through his efforts at quantifying behavior in addition to natural and physical phenomena (including the uniqueness of human fingerprints). Galton was the first person to really recognize some of the ramifications that Darwin’s theories had for understanding humans. He believed that intelligence was (largely) hereditary and that according to principles of natural selection, the most intelligent people should be the most influential in society even if their environment was not ideal; he thought that the most intelligent people were the most evolved. He was able to demonstrate that intelligence did appear to be hereditary by researching the families of eminent men and women. He estimated that preeminence occurred in about 1 in 4000 people but that people who were related to eminent men and women were more likely to be eminent themselves.
He expanded on this method by studying twins (a common method for understanding heritable factors today). He demonstrated that, even when living in different environments, twins more often than not had very similar propensities. Galton really was the scientist who injected the ideas of evolution into the study of human behavior and attributes. Most intelligence testing today traces its roots back to Galton and his ideas of individual differences and heritability.