A developmental model for the evolution of language and intelligence in early hominids

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Abstract
This paper presents a model for the nature and adaptive significance of intelligence and language in early hominids based on comparative developmental, ecological, and neurological data. We propose that the common ancestor of the great apes and man displayed rudimentary forms of late sensorimotor and early preoperational intelligence similar to that of one- to four-year-old children. These abilities arose as adaptations for extractive foraging with tools, which requires a long postweaning apprenticeship. They were elaborated in the first hominids with the shift to primary dependence on this feeding strategy. These first hominids evolved a protolanguage, similar to that of two-year-old human children, with which they could describe the nature and location of food and request help in obtaining it. The descendents of the first hominids displayed intuitive intelligence, similar to that of four- to seven-year-old children, which arose as an adaptation for complex hunting involving aimed-missile throwing, stone-tool manufacture, animal butchery, food division, and shelter construction. The comparative developmental and paleontological data are consistent with the hypothesis that the stages of development of intelligence and language and their neural substrates in our species recapitulate the stages of their evolution.