In order to account for some key structures in immigrant Spanish, 15th-16th-century African Portuguese, pidgin Portuguese, and the Portuguese-based creoles, we appeal to a model of Emergent Grammar in which linguistic structure emerges from frequency and perceptual saliency. We argue that key traits of the Portuguese-based creoles evolved from L2 varieties of Portuguese initially spoken by Africans in Portugal in the 15th and 16th centuries. First, we show how certain verb forms make their way into the speech of immigrants due to frequency of occurrence of verb forms based on their respective verb class. We also note that some forms become part of immigrant speech because of their more perceptually salient form (e.g. son over es, and são over é). Second, we point out that the many traits that characterize Chinese immigrant Spanish also define African Portuguese, and are those that also have found their way into the Portuguese-based creoles. We claim that regardless of whether pidgin Portuguese had its beginnings in Portugal or emerged in the interaction between the Portuguese and Africans in Africa, the same relative frequency of occurrence of forms would apply, as would the same processes used in naturalistic L2 acquisition, including sensitivity on the part of the speakers/learners to perceptual saliency of items. Thus, this study contributes to the understanding of the role that naturalistic L2 acquisition played in the formation of the pidgin Portuguese and, subsequently, the Portuguese-based creoles.