This paper examines language as a multimodal sensory enhancement system, integrating recent neuroanatomical and neurophysiological findings on the ontogenesis of neuronal structures with the generative concept of Universal Grammar (UG) for determination of fundamental differences between primary (PLA) and secondary (SLA) language acquisition. Substantial attention is given to general neurobiological principles such as experience expectant/dependent synaptogenesis, formational/organizational versus associational/reactive plasticity, characteristics of modular cortical organization, and general epigenetic qualities (e.g., intra- and interhemispheric competition, selective neuronal preservation, etc.) of the developing brain. Special emphasis is placed on neurobiological specializations relative to language (e.g., interhemispheric differences in dendritic arborization in Broca's area). The assumed innateness of UG is critically examined, with the neurobiological evidence indicating (a) the first language (L1) does not equal the second language (L2) neurobiologically, and (b) epigenetic factors contributing to PLA are often underestimated. The relevance of these conclusions for SLA is also briefly discussed.