Prosociality, in the eyes of some evolution theorists, is seen as the key to understanding the success of humanity, being a factor found present from the first months of child development. The objective behind the present thesis is to investigate the effect of ethnic and social exclusion on prosocial behavior in Brazilian children. In order to achieve this goal, use was made of implicit and explicit measures. The first chapter brings a theoretical review of the theories of evolution that cover prosocial behavior, and which focus on the theory of cultural evolution. The second chapter is composed of a systematic review of studies that investigate the effects of priming on prosocial behavior in children. The third chapter comprises of three empirical studies that analyze, (1) the association between sharing and the racial identification of the child, (2) the effect of ethnicity in prosocial priming, and (3) the choice of a black or white character as friends. Our findings pointed to an association between the racial identification of the child and sharing; an increase in sharing under the condition with prosocial priming, regardless of racial bias; and the preference of a white character as a friend. The fourth chapter reports on the construction and validation of the Implicit Association Test for assessing prosociality in children (IAT-PSC). The test presented good internal consistency and a satisfactory validation of the items. The fifth chapter is comprised of two studies, in which the participants are children that reside in urban areas, rural zones and in quilombo communities. The results demonstrate greater sharing among urban children, but greater implicit prosocial preference among children from quilombo communities. When taken together, our studies suggest that ostracism, racial exclusion and group belonging are factors that influence prosocial behavior in children, both explicitly and implicitly.