Before Darwin’s publication of On the Origin of Species by Means of Natural Selection in 1859, most human characteristics such as talent, personalities, and moral behaviors were thought to be acquired through environmental influences such as family, education, cultural training, and other factors described as “nurture.” However, Francis Galton (Darwin’s half-cousin) had observed that many physiological characteristics in animals are passed from generation to generation through a process called “inheritance.”
Inspired by the concept of inheritance of characteristics in the human species, Galton set out to investigate the relationships between the characteristics of parents and their offspring. In his 1869 publication Hereditary Genius, he presented data on eminent men and their sons, claiming that men of high eminence were more likely to have eminent sons than men who had not attained eminence, thereby demonstrating that eminence is a heritable quality. In a letter to Galton, Darwin wrote, “You have made a convert of an opponent in one sense, for I have always maintained that, excepting fools, men did not differ much in intellect, only in zeal and hard work.” However, Galton’s conclusions were challenged by others who argued that sons of eminent men had obvious social advantages in achieving eminence and that eminence itself was a subjective concept. These were the seeds of an acrimonious debate that would come into full flower a century later.
Until the later part of the 20th century, this controversy became known as the nature vs. nurture debate and it was fuelled by opposing ideologies. The egalitarians, attempting to dispel any justification for the existence of different social classes, argued that differences in human achievement were unrelated to inherited abilities and were entirely attributable to environmental influences like education, opportunity and hard work. The hereditarians, on the other hand, argued that intelligence was strongly influenced by genetic inheritance.
In 1990, Thomas J. Bouchard et al. published a seminal article titled, Sources of Human Psychological Differences: The Minnesota Study of Twins Reared Apart in which they assembled 100 sets of identical twins who were separated early in life and raised apart. All participants in the study completed about 50 hours of medical and psychological assessment.
Since identical twins come from a single fertilized egg, they share virtually 100% of their alleles and can be considered to be genetically identical. Furthermore, since they were raised apart, the differences in their IQ, when tested at the end of their separation must have been entirely attributable to environmental factors.
The researchers reported “about 70% of the variance in IQ was found to be associated with genetic variation.” The authors cautioned that this finding did not imply that IQ cannot be enhanced by rich experiences. In fact, they asserted that IQ scores can be increased by environmental influences. At least 5 subsequent studies involving samples of identical twins in the United States and Europe, who were reared apart, yielded heritabilities of IQ between 0.68 and 0.71, confirming the findings in the Minnesota study.
This would suggest that success in academic fields like theoretical physics, mathematics and computer science, where high intelligence a prerequisite, is significantly attributable to inherited intellectual potential. But what about success in a business enterprise? Psychologist Gene Landrum in a comprehensive study of the most successful entrepreneurs in the last 100 years, reveals in his book Entrepreneurial Genius: The Power of Passion, that higher than average intelligence is important, but it is less a factor in achieving success than other qualities such as passion, risk tolerance, work ethic and intuition.
So, it seems that your genetics provides you with some mental and physical proclivities that may stack the odds of success in your favor, but other factors including early imprints, family environment and desire play a more dominant role for success in many fields.
