Human Nature

, Volume 21, Issue 1, pp 62–81 | Cite as

Resource Competition and Reproduction in Karo Batak Villages

  • Geoff Kushnick


When wealth is heritable, parents may manipulate family size to optimize the trade-off between more relatively poor offspring and fewer relatively rich ones, and channel less care into offspring that compete with siblings. These hypotheses were tested with quantitative ethnographic data collected among the Karo Batak—patrilineal agriculturalists from North Sumatra, Indonesia, among whom land is bequeathed equally to sons. It was predicted that landholding would moderate the relationship between reproductive rate and parental investment on one hand, and the number of same-sex siblings on the other, among boys but not girls. The predicted interaction effect was observed in interbirth intervals and immunizations, but only a trace of the effect was detected in age-five mortality. The study raises questions about the coevolution of human behavior and social structure.


Interbirth intervals Patrilineality Landownership Inheritance Child health 



I thank the people of Doulu and Laubuluh villages for patiently enduring my prodding. I thank Eric Alden Smith (EAS), Monique Borgerhoff Mulder, Emily Brunson, Warren Miller, and three anonymous reviewers for providing useful suggestions. Fieldwork was funded by a National Science Foundation Dissertation Improvement Grant (0003951) awarded to me and EAS, and a “Seed” Grant from the Andrew W. Mellon Foundation. Research in Indonesia was done under the auspices of the Indonesian Academy of Sciences (Lembaga Ilmu Pengetahuan Indonesia, or LIPI) in Jakarta, with sponsorship from the late Amir Syamsu Nadapdap (Department of Anthropology, University of North Sumatra, Medan) and Aswatini Raharto (Center for Population and Manpower Studies, LIPI).


  1. Badan Pusat Statistik. (1998). Kabupaten Karo dalam angka, 1998. Berastagi: BPS.Google Scholar
  2. Badan Pusat Statistik and ORC Macro. (2003). Indonesia demographic and health survey, 2002-2003. Calverton: ORC Macro.Google Scholar
  3. Boone, J., & Kessler, K. (1999). More status or more children? Social status, fertility reduction, and long-term fitness. Evolution and Human Behavior, 20, 257–277.CrossRefGoogle Scholar
  4. Borgerhoff Mulder, M. (1991). Human behavioural ecology. In J. Krebs & N. Davies (Eds.), Behavioural ecology: An evolutionary approach (3rd ed., pp. 69–98). Boston: Blackwell.Google Scholar
  5. Borgerhoff Mulder, M. (1992). Reproductive decisions. In E. Smith & B. Winterhalder (Eds.), Evolutionary ecology and human behavior (pp. 339–374). Hawthorne: Aldine de Gruyter.Google Scholar
  6. Borgerhoff Mulder, M. (1998). Brothers and sisters: How sibling interactions affect optimal parental allocations. Human Nature, 9, 119–162.CrossRefGoogle Scholar
  7. Borgerhoff Mulder, M. (2000). Optimizing offspring: The quantity-quality tradeoff in agropastoralist Kipsigis. Evolution and Human Behavior, 21, 391–410.CrossRefGoogle Scholar
  8. Borgerhoff Mulder, M. (2007). Hamilton’s rule and kin competition: The Kipsigis case. Evolution and Human Behavior, 28, 299–312.CrossRefGoogle Scholar
  9. Box-Steffensmeier, J., & Jones, B. (2004). Event history modeling: A guide for social scientists. New York: Cambridge University Press.Google Scholar
  10. Clark, A. (1978). Sex ratio and local resource competition in a prosimian primate. Science, 201, 163–165.CrossRefGoogle Scholar
  11. Cleves, M., Gould, W., Guttierrez, R., & Marchenko, Y. (2008). An introduction to survival analysis using Stata (2nd ed.). College Station: Stata.Google Scholar
  12. Clutton Brock, T. (1991). The evolution of parental care. Princeton: Princeton University Press.Google Scholar
  13. Collier, G. (1975). The fields of Tzotzil: The ecological basis of tradition in highland Chiapas. Austin: University of Texas Press.Google Scholar
  14. Cronk, L. (1991a). Preferential parental investment in daughters over sons. Human Nature, 2, 387–417.CrossRefGoogle Scholar
  15. Cronk, L. (1991b). Intention versus behaviour in parental sex preferences among the Mukogodo of Kenya. Journal of Biosocial Science, 23, 229–240.CrossRefGoogle Scholar
  16. Cronk, L. (1991c). Human behavioral ecology. Annual Review of Anthropology, 20, 25–53.CrossRefGoogle Scholar
  17. Cronk, L. (1999). That complex whole: Culture and the evolution of human behavior. Boulder: Westview.Google Scholar
  18. Cronk, L. (2007). Boy or girl: Gender preferences from a Darwinian point of view. Ethics, Bioscience and Life, 15, 23–32.Google Scholar
  19. Gadgil, M., & Bossert, W. (1970). Life historical consequences of natural selection. American Naturalist, 104, 1–24.CrossRefGoogle Scholar
  20. Gelman, A., & Hill, J. (2007). Data analysis using regression and multilevel/hierarchical models. New York: Cambridge University Press.Google Scholar
  21. Hamilton, W. (1967). Extraordinary sex ratios. Science, 156, 477–488.CrossRefGoogle Scholar
  22. Hrdy, S., & Judge, D. (1993). Darwin and the puzzle of primogeniture: An essay on biases in parental investment after death. Human Nature, 4, 1–45.CrossRefGoogle Scholar
  23. Ihromi, T. (1994). Inheritance and equal rights for Toba Batak daughters. Law and Society Review, 28, 525–37.CrossRefGoogle Scholar
  24. Jaccard, J., & Turrisi, R. (2003). Interaction effects in multiple regression. Quantitative applications in the social sciences, 07-072 (2nd ed.). Thousand Oaks: Sage.Google Scholar
  25. Kipp, R. (1987). Karo Batak rice rituals then and now. In R. Carle (Ed.), Cultures and societies of North Sumatra (pp. 253–273). Berlin: Dietrich Reimer Verlag.Google Scholar
  26. Kipp, R. (1993). Dissociated identities: Ethnicity, religion, and class in an Indonesian society. Ann Arbor: University of Michigan Press.Google Scholar
  27. Kushnick, G. (2006). Parent-offspring conflict among the Karo of North Sumatra. PhD dissertation, Anthropology, University of Washington, Seattle.Google Scholar
  28. Lancaster, J., & Lancaster, C. (1987). The watershed: Change in parental-investment and family-formation strategies in the course of human evolution. In J. Altmann, A. Rossi, & L. Sherrod (Eds.), Parenting across the lifespan: Biosocial dimensions (pp. 187–205). New York: Aldine de Gruyter.Google Scholar
  29. Loeb, E. (1935). Sumatra: Its history and people. Oxford: Oxford University Press.Google Scholar
  30. Low, B. (1990). Occupational status, landownership, and reproductive behavior in 19th-century Sweden: Tuna Parish. American Anthropologist, 92, 457–468.CrossRefGoogle Scholar
  31. Low, B. (1991). Reproductive life in nineteenth century Sweden: An evolutionary perspective on demographic phenomena. Ethology and Sociobiology, 12, 411–448.CrossRefGoogle Scholar
  32. Low, B., & Clarke, A. (1991). Family patterns in nineteenth-century Sweden: Impact of occupational status and landownership. Journal of Family History, 16, 117–38.Google Scholar
  33. Lycett, J., Dunbar, R., & Voland, E. (2000). Longevity and the costs of reproduction in a historical human population. Proceedings of the Royal Society of London B, 267, 31–35.CrossRefGoogle Scholar
  34. Mace, R. (1998). The coevolution of human fertility and wealth inheritance strategies. Philosophical Transactions of the Royal Society of London B, 353, 389–397.CrossRefGoogle Scholar
  35. Mace, R. (2000). Evolutionary ecology of human life history. Animal Behaviour, 29, 1–10.CrossRefGoogle Scholar
  36. Palloni, A., & Tienda, M. (1986). The effects of breastfeeding and pace of childbearing on mortality at early ages. Demography, 23, 31–52.CrossRefGoogle Scholar
  37. Penny, D. H., & Singarimbun, M. (1967). Economic activity among the Karo Batak of Indonesia: A case study of economic change. Bulletin of Indonesia Economic Studies, 6, 31–65.CrossRefGoogle Scholar
  38. Pianka, E., & Parker, G. (1975). Age-specific reproductive tactics. American Naturalist, 109, 453–464.CrossRefGoogle Scholar
  39. Portier, M. K., & Slaats, H. (1987). Women and the division of parental land in Karo Society. In R. Carle (Ed.), Cultures and societies of North Sumatra (pp. 303–308). Berlin: Dietrich Reimer Verlag.Google Scholar
  40. Quinlan, R., Quinlan, M., & Flinn, M. (2003). Parental investment and age at weaning in a Caribbean village. Evolution and Human Behavior, 24, 1–16.CrossRefGoogle Scholar
  41. Rabe-Hesketh, S., & Skrondal, A. (2008). Multilevel and longitudinal modeling using Stata (2nd ed.). College Station: Stata.Google Scholar
  42. Rogers, A. (1994). For love or money: On the evolution of economic motivations in humans. In R. Dunbar (Ed.), Human reproductive decisions: Biological and social perspectives (pp. 76–95). London: St. Martin’s.Google Scholar
  43. Sieff, D. (1990). Explaining biased sex ratios in human populations: A critique of recent studies. Current Anthropology, 31, 25–48.CrossRefGoogle Scholar
  44. Silk, J. (1983). Local resource competition and facultative adjustment of sex ratios in relation to competitive abilities. American Naturalist, 121, 56–66.CrossRefGoogle Scholar
  45. Singarimbun, M. (1975). Kinship, descent, and alliance among the Karo Batak. Berkeley: University of California Press.Google Scholar
  46. Smith, E. (2000). Three styles in the evolutionary analysis of human behavior. In L. Cronk, W. Irons, & N. Chagnon (Eds.), Human behavior and adaptation: An anthropological perspective (pp. 27–46). Hawthorne: Aldine de Gruyter.Google Scholar
  47. Smith, C., & Fretwell, S. (1974). The optimal balance between size and number of offspring. American Naturalist, 108, 499–506.CrossRefGoogle Scholar
  48. Smith, E., & Winterhalder, B. (Eds.). (1992). Evolutionary ecology and human behavior. Hawthorne: Aldine de Gruyter.Google Scholar
  49. Steedly, M. (1993). Hanging without a rope: Narrative experience in colonial and postcolonial Karoland. Princeton: Princeton University Press.Google Scholar
  50. Trivers, R. (1972). Parental investment and sexual selection. In B. Campbell (Ed.), Sexual selection and the descent of man, 1871–1971 (pp. 136–179). Chicago: Aldine.Google Scholar
  51. Trivers, R., & Willard, D. (1973). Natural selection of parental ability to vary the sex ratio of offspring. Science, 179, 90–91.CrossRefGoogle Scholar
  52. Van Schaik, C., & Hrdy, S. (1991). Intensity of local resource competition shapes the relationship between maternal rank and sex ratios at birth in cercopithecine primates. American Naturalist, 138, 1555–1562.CrossRefGoogle Scholar
  53. Voland, E. (1995). Reproductive decisions viewed from an evolutionarily informed historical demography. In R. Dunbar (Ed.), Human reproductive decisions: Biological and social perspectives (pp. 137–159). London: St. Martin’s.Google Scholar
  54. Voland, E. (1998). Evolutionary ecology of human reproduction. Annual Review Anthropology, 27, 347–374.CrossRefGoogle Scholar
  55. Voland, E., & Dunbar, R. (1995). Resource competition and reproduction: The relationship between economic and parental strategies in the Krummhörn Population (1720–1874). Human Nature, 6, 33–49.CrossRefGoogle Scholar
  56. Williams, G. (1966). Natural selection, the costs of reproduction, and a refinement of Lack's principle. American Naturalist, 100, 687–690.CrossRefGoogle Scholar
  57. Winterhalder, B., & Smith, E. (2000). Analyzing adaptive strategies: Human behavioral ecology at twenty five. Evolutionary Anthropology, 9, 51–72.CrossRefGoogle Scholar

Copyright information

© Springer Science + Business Media, LLC 2010

Authors and Affiliations

  1. 1.Department of AnthropologyUniversity of Washington, SeattleSeattleUSA

Personalised recommendations