Seeking clues in brain development to explain the extraordinary evolution of language in humans

There has undoubtedly been a quantum leap forward in the evolution of cognitive processing in the human brain that has uniquely granted our species the use of syntactically complex language, however, the building blocks are present earlier in evolution suggesting that language may derive from our genes, and thus brains have evolved to embody a knowledge of Universal Grammar. Gene expression changes in development are the most likely to cause such macro-evolutionary alterations in neural circuits, and in this review I explore four areas of development predicted to be of importance. Firstly, there has been an increase in size and gyrification of the cerebral cortex. Secondly, there is increased connectivity between functional areas of the cortex, an expanded role for the subplate in guiding this process, and changes in synapse formation. Thirdly, the role of GABAergic interneurons in modulating functional connectivity has been enhanced and an elaboration in the developmental origins of interneurons may have led to an increased repertoire of functional subtypes. Finally, the development of lateralisation of language function is also briefly considered.