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The determinants and consequences of women’s fertility preferences and fertility in a rapidly acculturating Amerindian population

  • Author(s): McAllister, Lisa Sheina
  • Advisor(s): Gurven, Michael
  • et al.
Abstract

Teenage pregnancy, short interbirth intervals and high fertility are associated with a host of poor health and socioeconomic outcomes for mothers and their children. International population policies espouse that reducing mortality risk and increasing women’s educational attainment encourages delayed reproduction, prolongs interbirth intervals and lowers fertility. This is consistent with evolutionary theorizing. Life history theory suggests that reproductive timing and effort is influenced by mortality risk and resource access. When mortality risk declines, returns to investments in own and children’s embodied capital increase. As individuals move from a subsistence to a market based economy prolonged investment in embodied capital, specifically education, increasingly predicts adult resource accruement.

However, health and education initiatives in developing countries have inconsistent results. Examining the proximate mechanisms by which cues of mortality and education attainment influence reproductive timing may elucidate why failures occurred, and advance theory. This dissertation examines, within an Amerindian forager-farmer population: (1) how individual differences in mortality experiences and perceptions influence reproductive timing and effort; (2) whether education can effectively encourage delayed reproduction without returns to investments in educational capital; and (3) if precocious reproduction is a rational choice.

This research presents data from interviews conducted with 177 Tsimane women from 2010-2011, supplemented with reproductive history and anthropometric data from the Tsimane Health and Life History Project. Mortality risk whether perceived or experienced influences women’s reproductive preferences and behaviours, but not as theory predicts. For example, perceived mortality risk predicted later, not earlier, preferred age of first birth; and exposure to older sibling deaths delayed first births, while exposure to younger sibling deaths prompted first births. Greater educational attainment did not predict preferences for delayed reproduction; however, women who perceived higher returns to investments in educational capital preferred older ages of first birth. In summary, perceptions of mortality risk and returns to investment in educational capital influence reproductive timing, but complicate simplistic predictions from life history and embodied capital theories.

Despite equivocal relationships between mortality risk, educational attainment, and age of first birth, precocious reproduction may benefit Tsimane maternal reproductive fitness. In a population where kinship size affects resource access and socio-political power, and children provide labor and care in old age, high fertility women are the most successful. Until returns to investments in embodied capital are realized women may be unmotivated to delay reproduction, and may utilize improvements in health or resource access to reproduce earlier and increase their fertility.

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