Answer:
The period after emancipation marked the rise of scientific racism and the concept of race as a biological determinant of human abilities, traits and capacities. This new, "scientific" understanding of race is known as:
• Racial essentialism - The notion that racial groups possess intrinsic, genetically determined qualities that distinguish them as superior or inferior. Racial groups were seen as having fixed, inherent "essences" that shaped their attributes and behaviors.
• Racial hierarchy - The idea that racial groups could be ranked on an evolutionary scale based on assumed innate intellectual, moral and cultural capacities. Whites were placed at the top, followed by other groups.
• Scientific racism - The use of pseudoscientific theories, research and classification systems to argue that racial differences were inborn and immutable. This supposedly "proved" the superiority of whites and inferiority of nonwhites.
• Racialization - The process of ascribing particular biological characteristics and capacities to racial groups, transforming socially constructed race into an inherent biological reality. This "naturalized" racial differences and hierarchies.
These racial ideologies arose and gained credibility in the late 1800s, following the end of slavery. They provided a veneer of scientific validity for racist attitudes, discrimination and segregationist policies. They endured for decades, influencing institutions and popular thought well into the 20th century.
So the post-emancipation period marked a shift from race being based primarily on social and legal categories to becoming rooted in purported biological and genetic differences. This "new racism" justified the continuation of racial inequity in the supposed name of science.