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Reading Week 5 - Caspari - 44 Scientific American August...

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44 Scientific American, August 2011 Photograph by Tktk Tktk
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August 2011, ScientificAmerican.com 45 HUMAN ORIGINS the evolution of grandparents Senior citizens may have been the secret of our species’ success By Rachel Caspari Rachel Caspari is a professor of anthropology at Central Michigan University. Her research focuses on Neandertals, the origin of modern humans and the evolution of longevity. I N B R I E F People today typically live long enough to become grandparents, but this was not always the case. Recent analyses of fossil teeth indicate that grand- parents were rare in ancient populations, such as those of the australopithecines and the Neandertals. They first became common around 30,000 years ago, as evidenced by remains of early modern Europeans. This surge i n the number of seniors may have been a driving force for the explosion of new tool types and art forms that occurred in Europe at around the same time. It also may explain how modern humans out- competed archaic groups such as the Neandertals. Illustration by Viktor Deak
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46 Scientific American, August 2011 D uring the summer of 1963 , when i was six years old, my family traveled from our home in Philadelphia to Los Angeles to visit my maternal rela- tives. I already knew my grandmother well: she helped my mother care for my twin brothers, who were only 18 months my junior, and me. When she was not with us, my grandmother lived with her mother, whom I met that summer for the first time. I come from a long-lived family. My grandmoth- er was born in 1895, and her mother in the 1860s; both lived almost 100 years. We stayed with the two matriarchs for several weeks. Through their stories, I learned about my roots and where I belonged in a social network spanning four generations. Their reminiscences personally connected me to life at the end of the Civil War and the Reconstruc- tion era and to the challenges my ancestors faced and the ways they persevered. My story is not unique. Elders play critical roles in human societies around the globe, conveying wisdom and providing social and economic support for the families of their children and larger kin groups. In our modern era, people routinely live long enough to become grandparents. But this was not always the case. When did grandparents become prevalent, and how did their ubiquity affect human evolution? Research my colleagues and I have been conducting indi- cates that grandparent-aged individuals became common rela- tively recently in human prehistory and that this change came at about the same time as cultural shifts toward distinctly mod- ern behaviors—including a dependence on sophisticated sym- bol-based communication of the kind that underpins art and language. These findings suggest that living to an older age had profound effects on the population sizes, social interactions and genetics of early modern human groups and may explain why they were more successful than archaic humans, such as the Neandertals.
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