Corballis suggests that fully vocal communication was invented by modern humans between 170,000 and 50,000 years ago. Because this new form of communication did not require hand gestures, he wondered whether this may have facilitated the development of lithic manufacture. I cast doubt on this interesting notion but offer an enhanced version that may have more potential.

We argue that lateralities are not merely a result of phylogenetic processes but reflect probability functions that are influenced by task characteristics and extended practice. We support our argument by empirical findings on lateral biases in early infancy in general, and footedness in particular, and on hand preferences in nonhuman primates.

Charmed by Corballis's presentation, we challenge the use of mirror neurons as a supporting platform for the gestural theory of language, the link between vocalization and cerebral specialization, and the relationship between gesture and language as two separate albeit coupled systems of communication. We revive an alternative explanation of lateralization of language and handedness.

I would like to stress that early development repeats the evolution of the species. Hence, to understand the origins of functional brain asymmetry and the underlying mechanisms involved in handedness, we have to seek information not only from what we know about human evolution, but also from how an early hand preference develops in our own species.

In this commentary we argue that evolution of the human brain to host the language system was accomplished by the selective development of frontal and temporal areas in the left hemisphere. The unilateral development of Broca's and Wernicke's areas could have resulted from one or more transcription factors that have an expression pattern restricted to the left hemisphere.

I do not disagree with the argument that human-population right-handedness may in some way be a consequence of the population-level left-lateralization of language. But I suggest that the human functional lateralization is not dependent on the structural left-right brain asymmetries to which Corballis refers.

Although gestures have surface similarities with language, there are significant organisational and neurolinguistic differences that argue against the evolutionary connection proposed by Corballis. Dominance for language and handedness may be related to a basic specialisation of the left cerebral hemisphere for target-directed behaviour and sequential processing, with the right side specialised for holistic-environmental monitoring and spatial processing.

Toolmaking requires motor skills that in turn require handedness, so that there is no competition between the two sides of the brain. Thus, handedness is not necessarily linked to vocalization but to the origin of causal beliefs required for making complex tools. Language may have evolved from these processes.

Many commentators have raised issues concerning the idea that language evolved from manual gestures. I deal with these first, reiterating the points that speech is very different from animal vocal calls, and that cortical control over manual action provided the best platform for the evolution of intentional communication and language. I then deal with commentaries on the origins of handedness. The critical questions are whether there is indeed an evolutionary coupling between handedness and lateralized control of speech, and if there is, whether a prior lateralization of vocal control provided the nudge that gave most of us left-sided speech and right-handedness.