Studies of whites by thomas pettigrew in south africa in the 1950s, when apartheid ruled, revealed that those who were also the most prejudiced

Conformed to other social norms is the correct answer.

Thomas Pettigrew was a Social Psychologist who made great observations regarding the apartheid and race interactions. According to him, prejudice is minimized when social interactions take place, so prejudice escalated when apartheid restricted contact among races. And, also, his studies suggested that those who conformed to other's social norms were the ones that were prejudiced the most.

the answer to your question is,

old stone age.

-mabel < 3