This chapter is concerned with the question of the relations and possible influences of environmental factors on the establishment of patterns of manual lateralization in human and non-human primates. More specifically, we are interested in the relation between maternal postures and laterality in nonhuman primates (e.g. bias in cradling behaviour and hand preference of the mother) and the development of patterns of manual preferences in infants. In order to understand fully the many ways in which these variables could interact, we first review the evidence of postural biases in human adults when cradling and carrying their offspring. Next, we examine the divergent hypotheses advanced to explain the observed biases. The same is then done for non-human primates. A second part of our chapter describes the different asymmetric patterns observed during the development of the infant concerning head turning, nipple preference, etc. in both human and non-human primates. In a third part ..