Wealth in Human Evolution and Human History

This chapter presents a theory of brain and life span evolution and applies it to both primates in general, and to the hominid line, in particular. To address the simultaneous effects of natural selection on the brain and on the life span, it extends the standard life history theory in biology which organizes research into the evolutionary forces shaping age-schedules of fertility and mortality. This extension, the embodied capital theory, integrates existing models with an economic analysis of capital investments and the value of life. The chapter begins with a brief introduction to embodied capital theory, and then applies it to understanding major trends in primate evolution and the specific characteristics of humans. The evolution of brain size, intelligence, and life histories in the primate order are addressed first. The evolution of the human life course is then considered, with a specific focus on the relationship between cognitive development, economic productivity, and longevity. It will be argued that the evolution of the human brain entailed a series of coevolutionary responses in human development and aging. The second section on embodied capital and extrasomatic wealth discusses humans in a comparative context, beginning with the hunting and gathering lifestyle because of its relevance to the vast majority of human evolutionary history. However, in the past 10 000 years human history traced a series of behavioral adaptations based on ecology and individual condition. The introduction of extra-somatic capital, first in the form of livestock and later in land and other types of wealth and power, radically changed the shape of human life history parameters and produced new patterns of fertility, parental investment, and reproductive regimes as access to extra-somatic capital became a focus of life history strategies. Finally, modern skills-based, competitive labor markets, combined with reduced fertility during the nineteenth century,mark a returning focus on embodied capital in the form of skills, education, and training. In past civilizations, going back to Babylonia in the third millennia BC, literacy and numeracy were known but exceedingly rare skills. This pattern continued worldwide until 1800 in Western Europe, including England, where these skills went from rarity to the norm in under a century (Clark, 2007). Labor markets with a particular demand for embodied capital in their workers place new demands on human life history and reproductive strategies in terms of mate choice, fertility, investment in children, and the timing of reproduction in the life course. Once again, human life history radically changed in shape to a new emphasis on the acquisition of skills through training and education, postponement of reproduction to the late 20s, and radically reduced completed family size with the reproductive part of the life course compressed into less than a decade.