Human behaviour is influnced by both culture and biology. Nurture implies a possibility of change, while nature is more fixed - an how the weight assigned to one factor or the other varies with the specific behaviour being explained. Women could expect to live 81, when men is 76. Since when deaths from preventable causes, such as unsafe sex, poor driving, smoking, and excessive drinking, are factored out, the gap reverses and men have a slight advantage. Social variables also affect the gender gap. Different sized gaps in different ethnic groups in the same society also suggest social influnences. Five and a half year ga does not mean that all women outlive all men. Within variation (comparing males to males or females to females) Gender imbalances in post-secondary education are well documented. Female students are overrepresent in the humanities and social sciences, while male students are the majority in mathematics, technology and sciences.