The role of dispersal and school attendance on reproductive dynamics in small, dispersed populations: Choyeros of Baja California Sur, Mexico

PLoS One. 2020 Oct 7;15(10):e0239523. doi: 10.1371/journal.pone.0239523. eCollection 2020.

Abstract

Individuals from small populations face challenges to initiating reproduction because stochastic demographic processes create local mate scarcity. In response, flexible dispersal patterns that facilitate the movement of individuals across groups have been argued to reduce mate search costs and inbreeding depression. Furthermore, factors that aggregate dispersed peoples, such as rural schools, could lower mate search costs through expansion of mating markets. However, research suggests that dispersal and school attendance are costly to fertility, causing individuals to delay marriage and reproduction. Here, we investigate the role of dispersal and school attendance on marriage and reproductive outcomes using a sample of 54 married couples from four small, dispersed ranching communities in Baja California Sur, Mexico. Our analyses yield three sets of results that challenge conventional expectations. First, we find no evidence that dispersal is associated with later age at marriage or first reproduction for women. For men, dispersal is associated with younger ages of marriage than those who stay in their natal area. Second, in contrast to research suggesting that dispersal decreases inbreeding, we find that female dispersal is associated with an increase in genetic relatedness among marriage partners. This finding suggests that human dispersal promotes female social support from genetic kin in novel locales for raising offspring. Third, counter to typical results on the role of education on reproductive timing, school attendance is associated with younger age at marriage for men and younger age at first birth for women. While we temper causal interpretations and claims of generalizability beyond our study site given our small sample sizes (a feature of small populations), we nonetheless argue that factors like dispersal and school attendance, which are typically associated with delayed reproduction in large population, may actually lower mate search costs in small, dispersed populations with minimal access to labor markets.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Age Factors
  • Educational Status*
  • Environment
  • Female
  • Humans
  • Male
  • Marriage
  • Mexico
  • Population Dynamics*
  • Rural Population

Grants and funding

SJM and ES (HJ-099R-17) National Geographic Society Research and Exploration Grant. SJM (subcontractor 1743019) National Science Foundation IBSS-L (PI Koster) https://www.nsf.gov/awardsearch/showAward?AWD_ID=1743019&HistoricalAwards=false. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript. In addition, this research was supported through the following sources: Funding Incentive Seed Grant (University of Utah), the Center for Latin American Studies (University of Utah), Society, Water, & Climate Seed Grant (University of Utah), Nexus Pilot Grant (University of Utah), Economic Science Institute (Chapman University), and the Division of Anthropology (California State University Fullerton).