How do you explain the evolution of indentured servitude to hereditary slavery?

Rick is a toddler with an easy temperament and active nature. people are often seen stopping to talk to him in supermarkets and parks where his mother takes him in the evenings because he smiles willingly at other children and adults. this aspect of rick’s behavior most likely reflects a(n) active genotype–environment interaction suppressive genotype-environment interaction passive genotype–environment interaction evocative genotype–environment interaction