Concepts of race and sexuality have interacted in various ways in different historical contexts. While partially based on physical similarities within groups, race is understood by scientists to be a social construct rather than a biological reality. Human sexuality involves biological, erotic, physical, emotional, social, or spiritual feelings and behaviors. The ways in which people perceive the relationship between these two concepts implicitly informs attitudes toward interracial sexual relationships and sexual preferences for particular races expressed by individuals. Racial bias may involve a sexual dimension, which often takes the form of racial fetishism. After the abolition of slavery in 1865, white Americans showed an increasing fear of racial mixing. The remnants of the racial divide became stronger post-slavery as the concept of whiteness developed. There was a widely held belief that uncontrollable lust threatens the purity of the nation. This increased white anxiety about interracial sex, and has been described through Montesquieu's climatic theory in his book The Spirit of the Laws, which explains how people from different climates have different temperaments, "The inhabitants of warm countries are, like old men, timorous; the people in cold countries are, like young men, brave." At the time, black women held the "Jezebel" stereotype, which claimed black women often initiated sex outside of marriage and were generally sexually promiscuous. This idea stemmed from the first encounters between European men and African women. As the men were not used to the extremely hot climate, they misinterpreted the women's lack of clothing for vulgarity. Similarly, black men were stereotyped as having a specific lust for white women. This stereotype triggered tensions, implying that white men were having sex with black women because black women were more lustful than white women were, and in turn, black men would lust after white women in the same way that white men would lust after black women.