Introduction

In this chapter we present a general overview of the causes and consequences of migration in Brazilian Afro-derived rural communities. These communities, known in Brazil as Remanescentes de Quilombos, present some important characteristics that make them ideal models to study human migrations on a local scale, such as a distinct genetic constitution and also some degree of isolation. They were mainly formed by fugitive and freed African slaves and their descendants (Reis and Gomes, 1996). For this reason, African ancestry is predominant in their genetic composition (Bortolini et al., 1999) in contrast to other Brazilian populations, in which the European contribution is more pre-eminent (Godinho et al., 2008). Moreover, these communities were usually located at a considerable distance from urban centers, as a strategy for resisting slavery during colonial times (Reis and Gomes, 1996); nowadays, this confers them a certain degree of isolation (Souza and Culpi, 2005).

Our study seeks to relate the socioeconomic causes of the migratory behavior observed in these communities to the evolutionary consequences of gene flow at the population level, in order to understand the role of migration as an agent in the evolution of smallholder populations. We start this chapter by unraveling the history behind the first migrations of Africans to the Americas and then explain the current situation of the African descendants in Brazil, before a brief description of the communities here employed as models (Mocambo, Riacho de Sacutiaba e Sacutiaba, and Rio das Rãs). Next, there is a detailed description of the observed migratory patterns in these communities, followed by an analysis of admixture with uni- and biparental genetic markers. Finally, demographic and genetic data are crossed in order to propose new insights into the study of migrations in rural smallholder populations. We believe this might serve as a primary source for comparative studies of migration, providing guidance for assessing models of past and current human population mobility.