14 September 2013

The importance of old people in human cultural evolution

Excerpts from an article published by researchers at the University of Pennsylvania in the Proceedings of the National Academy of Science:
Increased longevity, expressed as number of individuals surviving to older adulthood, represents one of the ways the human life history pattern differs from other primates. We believe it is a critical demographic factor in the development of human culture. Here, we examine when changes in longevity occurred by assessing the ratio of older to younger adults in four hominid dental samples from successive time periods... there is a dramatic increase in longevity in the modern humans of the Early Upper Paleolithic. We believe that this great increase contributed to population expansions and cultural innovations associated with modernity...

Longevity, in particular, may be necessary for the transgenerational accumulation and transfer of information that allows for complex kinship systems and other social networks that are uniquely human...

However, whether the result of cultural factors, other forms of relaxed selection affecting the mortality of young adults, and/or biological change, the increase in adult survivorship would have considerable evolutionary impact... Increased adult survivorship strengthens those relationships and information transmission by extending the time over which people can learn from older individuals and by the increase in the number of older people, which promotes the acquisition and transmission of specialized knowledge such as that reflected in the Upper Paleolithic.

Not only does increased survivorship imply greater lifetime fertility for individuals, the investment of older individuals in their children's families may provide a selective advantage promoting further population increase.
Via The Dish.


  1. Stewart and Cohen talk about this in one of the "Science of Discworld" books. They consider the grandparent/-child bond so important a feature of human cultural transmission that they use 'one grandfather' (~50 years) as a handy benchmark for societal transformation over time. It gets dizzying quite quickly.

  2. Not surprising. The adults could let the Grandparents watch the kids while they went out hunting and gathering, thusly increasing the effective number of members of a band, and this would also increase the education (both quality and quantity) of the kids, and giving the elderly something useful to do. Smart.


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