Vaesen infers unique properties of mind from the appearance of specific cultural innovation – a correlation without causal direction. Shifts in habitat, population density, and group dynamics are the only independently verifiable incentives for changes in cultural practices. The transition from Acheulean to Late Stone Age technologies requires that we consider how population and social dynamics affect cultural innovation and mental function.

Languages emerge in response to the negotiation of shared meaning in social groups, where transparency of grammar is necessitated by demands of communication with relative strangers needing to consult on a wide range of topics (Ragir 2002). This communal exchange is automated and stabilized through activity-dependent fine-tuning of information-specific neural connections during postnatal growth and social development.

The uniqueness of human cognition and language has long been linked to systematic changes in developmental timing. Selection for postnatal skeletal ossification resulted in progressive prolongation of universal patterns of primate growth, lengthening infancy, childhood, and adolescence. Language emerged as communication increased in complexity within and between communities rather than from selection for some unique features of childhood or adolescence, or both.

The mechanics of walking restructured the pelvis and narrowed the birth-canal that selected for delays in skeletal ossification. Prolonged phases of fetal maturation increased the mass and volume of the brain relative to adult body-size, as encephalization increased. Thus, bipedal- walking and episodic increases in hominine body size probably triggered selection for neonatal skeletal immaturity that led to encephalization.