This question is part of a massive issue within social sciences which is known generally as the nature/nurture debate. To put it simply, the key issue surrounds whether who humans are the kind of people they become is a result of the powerful impact of their genetic code inherited from their parents or the environment in which they are brought up in and the context of their lives, most importantly their early years. This is a debate that continues to rage on and looks as if it will never be definitively answered. However, the majority of social sciences favour nurture as being the biggest influence, or the context in which a person is raised.
If nurture is considered as the most powerful influence, this is a very good thing, as it means that we can seek to change those contexts as appropriate in order to try and improve the life chances of certain groups of humans. For example, research shows very clearly that people coming from working class families on average do less well in education and go on to achieve a lower percentage of degrees than those from middle and upper class families. To argue that genes are the stronger force in this case means that this educational discrepancy is a result of the lack of intelligence of the working class. This is clearly a massively problematic view. If, however, the influence of our environment is seen as the strongest influence, then this influence can seek to be combatted through greater support for working class children whilst they are in school.