Hamilton WD. The moulding of senescence by natural selection. J Theor Biol. 1966; 12 (1): 12–45. 86 Kim PS, Coxworth JE, Hawkes K. Increased longevity evolves from grandmothering. Proc Biol Sci. 2012; 279 (1749): 4880-84. 87 Johnstone RA, Cant MA. The evolution of menopause in cetaceans and humans: the role of demography. Proc Biol Sci. 2010; 277 (1701): 3765-71. 88 Outhwaite RB. Population change, family structure and the good of counting. The Historical Journal. 1979; 22 (1): 229-37. 89 Bird DW, Bird BB. Children on the reef. Human Nature. 2002; 13 (2): 269-97. 90 Jones BJ, Marlowe FW. Selection for delayed maturity. Human Nature. 2002; 13 (2): 199–238. 91 Institute for Health Metrics and Evaluation. The State of US Health: Innovations, Insights, and Recommendations from the Global Burden of Disease Study. Seattle, WA: Institute for Health Metrics and Evaluation, University of Washington; 2013. 92 Whelan D. Cranking up the volume. Forbes. February 8, 2008. www.forbes.com/forbes/2008/0225/032.html. 93 United States Census Bureau. Fairfax County, Virginia. quickfacts.census.gov/qfd/states/51/51059.html. 2013. 94 United States Census Bureau. McDowell County, West Virginia. quickfacts.census.gov/qfd/states/54/54047.html. 2013. 95 Kochanek KD, Arias E, Anderson RN. How Did Cause of Death Contribute to Racial Differences in Life Expectancy in the United States in 2010? NCHS data brief, no. 125. Hyattsville, MD: National Center for Health Statistics; 2013. 96 Riley, Low Income. 97 Ariès P. Western Attitudes toward Death: From the Middle Ages to the Present. Johns Hopkins University Press; 1975.