Skip to main content
Log in

Does Kin-Selection Theory Help to Explain Support Networks among Farmers in South-Central Ethiopia?

  • Published:
Human Nature Aims and scope Submit manuscript

Abstract

Social support networks play a key role in human livelihood security, especially in vulnerable communities. Here we explore how evolutionary ideas of kin selection and intrahousehold resource competition can explain individual variation in daily support network size and composition in a south-central Ethiopian agricultural community. We consider both domestic and agricultural help across two generations with different wealth-transfer norms that yield different contexts for sibling competition. For farmers who inherited land rights from family, firstborns were more likely to report daily support from parents and to have larger nonparental kin networks (n = 180). Compared with other farmers, firstborns were also more likely to reciprocate their parents’ support, and to help nonparental kin without reciprocity. For farmers who received land rights from the government (n = 151), middle-born farmers reported more nonparental kin in their support networks compared with other farmers; nonreciprocal interactions were particularly common in both directions. This suggests a diversification of adult support networks to nonparental kin, possibly in response to a long-term parental investment disadvantage of being middle-born sons. In all instances, regardless of inheritance, lastborn farmers were the most disadvantaged in terms of kin support. Overall, we found that nonreciprocal interactions among farmers followed kin selection predictions. Direct reciprocity explained a substantial part of the support received from kin, suggesting the importance of the combined effects of kin selection and reciprocity for investment from kin.

This is a preview of subscription content, log in via an institution to check access.

Access this article

Price excludes VAT (USA)
Tax calculation will be finalised during checkout.

Instant access to the full article PDF.

Institutional subscriptions

Fig. 1
Fig. 2
Fig. 3

Similar content being viewed by others

References

  • Aldrich, D. (2012). Building resilience: Social capital in post disaster recovery. Chicago: University of Chicago Press.

    Google Scholar 

  • Aldrich, D., & Meyer, M. (2014). Social capital and community resilience. American Behavioral Scientist, 59, 254–269. https://doi.org/10.1177/0002764214550299.

    Article  Google Scholar 

  • Allen-Arave, W., Gurven, M., & Hill, K. (2008). Reciprocal altruism, rather than kin selection, maintains nepotistic food transfers on an Ache reservation. Evolution and Human Behavior, 29, 305–318.

    Google Scholar 

  • Alvergne, A., Lawson, D., Clarke, P., Gurmu, E., & Mace, R. (2012). Fertility, parental investment, and the early adoption of modern contraception in rural Ethiopia. American Journal of Human Biology., 25(1), 107–115.

    Google Scholar 

  • Bernard, H. (2002). Research methods in anthropology: Qualitative and quantitative approaches, fifth edition. Lanham, MD: Rowman & Littlefield.

  • Boone, J. (1986). Parental investment and elite family structure in preindustrial states: A case study of late medieval–early modern Portuguese genealogies. American Anthropologist, 88(4), 859–878.

    Google Scholar 

  • Boone, J. (1992). Competition, conflict, and the development of social hierarchies. In E. Smith & B. Winterhalder (Eds.), Evolutionary ecology and human behavior (pp. 301–337). Hawthorne: Aldine de Gruyter.

    Google Scholar 

  • Carter, G., & Wilkinson, G. (2013). Food sharing in vampire bats: Reciprocal help predicts donations more than relatedness or harassment. Proceedings of the Royal Society, 280, 20122573. https://doi.org/10.1098/rspb.2012.2573.

    Article  Google Scholar 

  • Caudell, M., Rotolo, T., & Grima, M. (2015). Informal lending networks in rural Ethiopia. Social Networks, 40, 34–42.

    Google Scholar 

  • Clarke, A., & Low, B. (1992). Ecological correlates of human dispersal in 19th century Sweden. Animal Behaviour, 44, 677–693.

    Google Scholar 

  • Clutton-Brock, T. (1984). Reproductive effort and terminal investment in iteroparous animals. The American Naturalist, 123(2), 212–229.

    Google Scholar 

  • Clutton-Brock, T. (2009). Cooperation between non-kin in animal societies. Nature, 462(7269), 51–57.

    Google Scholar 

  • Congdon Fors, H., Houngbedji, K., & Lindskog, L. (2019). Land certification and schooling in rural Ethiopia. World Development, 115, 190–208.

    Google Scholar 

  • Draper, P., & Hames, R. (2000). Birth order, sibling investment, and fertility among Ju/'hoansi (!Kung). Human Nature, 11(2), 117–156.

    Google Scholar 

  • Dunbar, R. (2008). Cognitive constraints on the structure and dynamics of social networks. Group Dynamics: Theory, Research, and Practice, 12(1), 7–16.

    Google Scholar 

  • Dunbar, R., & Spoors, M. (1995). Social networks, support cliques, and kinship. Human Nature, 6(3), 273–290.

    Google Scholar 

  • Fafchamps, M., & Lund, S. (2003). Risk-sharing networks in rural Philippines. Journal of Development Economics, 71(2), 261–287.

    Google Scholar 

  • Faurie, C., Russell, A., & Lummaa, V. (2009). Middleborns disadvantaged? Testing birth-order effects on fitness in pre-industrial Finns. PLoS One, 4(5), 56–80.

    Google Scholar 

  • Fowler, F. (1995). Improving survey questions: design and evaluation. Applied Social Research Series 38. Thousand Oaks: Sage.

  • Gavian, S., & Ehui, S. (1999). Measuring the production efficiency of alternative land tenure contracts in a mixed crop-livestock system in Ethiopia. Agricultural Economics, 20, 37–49.

    Google Scholar 

  • Gibson, M. (2002). Development and demographic change: The reproductive ecology of a rural Ethiopian Oromo population. PhD thesis, University College London.

  • Gibson, M., & Gurmu, E. (2011). Land inheritance establishes sibling competition for marriage and reproduction in rural Ethiopia. Proceedings of the National Academy of Sciences (USA), 108(6), 2200–2204.

    Google Scholar 

  • Gibson, M., & Gurmu, E. (2012). Rural to urban migration is an unforeseen impact of development intervention in Ethiopia. PLoS One, 7(11), e48708. https://doi.org/10.1371/journal.pone.0048708.

    Article  Google Scholar 

  • Gibson, M., & Lawson, D. (2011). Modernization increases parental investment and sibling resource competition: Evidence from a rural development initiative in Ethiopia. Evolution and Human Behavior, 32, 97–105.

    Google Scholar 

  • Gibson, M., & Sear, R. (2010). Does wealth increase parental investment biases in child education? Evidence from two African populations on the cusp of the fertility transition. Current Anthropology, 51, 693–701.

    Google Scholar 

  • Gurven, M., Hill, K., Kaplan, H., Hurtado, A., & Lyles, R. (2000). Food transfers among Hiwi foragers of Venezuela: Tests of reciprocity. Human Ecology, 28(2), 171–218.

    Google Scholar 

  • Hames, R. (1987). Garden labor exchange among the Ye’kwana. Ethology and Sociobiology, 8(4), 259–284.

    Google Scholar 

  • Hamilton, W. (1964). The genetical evolution of social behaviour. Journal of Theoretical Biology, 7(1), 1–16.

    Google Scholar 

  • Hamilton, M., Milne, B., Walker, R., Burger, O., & Brown, J. (2007). The complex structure of hunter-gatherer social networks. Proceedings of the Royal Society, 274, 2195–2203. https://doi.org/10.1098/rspb.2007.0564.

    Article  Google Scholar 

  • Hertwig, R., Davis, J., & Sulloway, F. (2002). Parental investment: How an equity motive can produce inequality. Psychological Bulletin, 128(5), 728–745.

    Google Scholar 

  • Hill, R., & Dunbar, R. (2003). Social network size in humans. Human Nature., 14(1), 53–72.

    Google Scholar 

  • Hrdy, S., & Judge, D. (1993). Darwin and the puzzle of primogeniture. Human Nature, 4(1), 1–45.

    Google Scholar 

  • Jaeggi, A., & Gurven, M. (2013). Reciprocity explains food sharing in humans and other primates independent of kin selection and tolerated scrounging: A phylogenetic meta-analysis. Proceedings of the Royal Society B, 280, 20131615. https://doi.org/10.1098/rspb.2013.1615.

    Article  Google Scholar 

  • Judge, D., & Hrdy, S. (1992). Allocation of accumulated resources among close kin: Inheritance in Sacramento, California, 1890-1984. Ethology and Sociobiology, 13, 495–522.

    Google Scholar 

  • Kidwell, J. (1982). The neglected birth order: Middleborns. Journal of Marriage and Family, 44(1), 225–235.

    Google Scholar 

  • Krosnick, J., & Fabrigar, L. (1997). Designing rating scales for effective measurement in surveys. In L. Lyberg, P. Biemer, M. Collins, E. De Leeuw, C. Dippo, N. Schwarz, & D. Trewin (Eds.), Survey measurement and process quality (pp. 141–164). Wiley Series in Probability and Statistics. New York: Wiley.

  • Lewis, J. (2010). Connecting and cooperating: Social capital and public policy. Sydney: University of New South Wales Press.

    Google Scholar 

  • Narayan, D., & Pritchett, L. (1999). Cents and sociability: Household income and social capital in rural Tanzania. Economic Development and Cultural Change, 47(4), 871–897.

    Google Scholar 

  • Patton, J. (2005). Meat sharing for coalitional support. Evolution and Human Behavior, 26, 137–157.

    Google Scholar 

  • Pollet, T., & Nettle, D. (2007). Birth order and face-to-face contact with a sibling: Firstborns have more contact than laterborns. Personality and Individual Differences, 43, 1796–1806.

    Google Scholar 

  • Pollet, T., & Nettle, D. (2009). Birth order and adult family relationships: Firstborns have better sibling relationships than laterborns. Journal of Social and Personal Relationships, 26(8), 1029–1046.

    Google Scholar 

  • Pretty, J. (2003). Social capital and the collective management of resources. Science, 302, 1912–1914.

    Google Scholar 

  • Putnam, R. (2000). Bowling alone: America’s declining social capital. In L. Crothers & C. Lockhart (Eds.), Culture and politics (pp. 223–234). New York: Palgrave Macmillan.

    Google Scholar 

  • Rohde, P., Atzwanger, K., Butovskaya, M., Lampert, A., Mysterud, I., Sanchez-Andres, A., & Sulloway, F. (2003). Perceived parental favoritism, closeness to kin, and the rebel of the family: The effects of birth order and sex. Evolution and Human Behavior, 24, 261–276.

    Google Scholar 

  • Salmon, C. (2003). Birth order and relationships. Human Nature, 14(1), 73–88.

    Google Scholar 

  • Salmon, C., & Daly, M. (1998). Birth order and familial sentiment: Middleborns are different. Evolution and Human Behavior, 19, 299–312.

    Google Scholar 

  • Santos, P., & Barrett, C. (2006). Informal insurance in the presence of poverty traps: Evidence from southern Ethiopia. Ithaca: Cornell University Working Paper.

    Google Scholar 

  • Smith, E., Borgerhoff Mulder, M., Bowles, S., Gurven, M., Hertz, T., & Shenk, M. (2010). Production systems, inheritance, and inequality in premodern societies: Conclusions. Current Anthropology, 51(1), 85–94.

    Google Scholar 

  • Stanton, M. A., Lonsdorf, E. V., Pusey, A. E., Goodall, J., & Murray, C. M. (2014). Maternal behavior by birth order in wild chimpanzees Pan troglodytes increased investment by first-time mothers. Current Anthropology, 55(4), 483–489.

    Google Scholar 

  • Strassman, B., & Clarke, A. (1998). Ecological constraints on marriage in rural Ireland. Evolution and Human Behavior, 19, 33–55.

    Google Scholar 

  • Sulloway, F. (1996). Born to rebel: Birth order, family dynamics, and creative lives. New York: Pantheon Books.

    Google Scholar 

  • Taborsky, M. (2013). Social evolution: Reciprocity there is. Current Biology, 23, R486–R488.

    Google Scholar 

  • Tefera, B., Ayele, G., Yigezu, A., Jabbar, M., & Dubale, P. (2002). Nature and causes of land degradation in the Oromiya region: A review. Socio-economics and Policy Research Working Paper 36. Nairobi: International Livestock Research Institute.

  • Towner, M. (2001). Linking dispersal and resources in humans: Life history from Oakham, Massachusetts (1750-1850). Human Nature, 12(4), 321–349.

    Google Scholar 

  • Trivers, R. (1971). The evolution of reciprocal altruism. The Quarterly Review of Biology, 46(1), 35–57.

    Google Scholar 

  • 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 

  • Trivers, R. (1974). Parent-offspring conflict. American Zoologist, 14(1), 249–264.

    Google Scholar 

  • Trivers, R., & Willard, D. (1973). Natural selection of parental ability to vary the sex ratio of offspring. Science, 179(4068), 90–92.

    Google Scholar 

  • Voland, E., & Dunbar, R. (1995). Resource competition and reproduction, the relationship between economic and parental strategies in the Krumhorn population (1720-1874). Human Nature, 6(1), 33–49.

    Google Scholar 

  • Zhou, W., Sornette, D., Hill, R., & Dunbar, R. (2005). Discrete hierarchical organization of social group sizes. Proceedings of the Royal Society B: Biological Sciences, 272(1561), 439–444.

    Google Scholar 

Download references

Acknowledgments

This work was funded by a Leverhulme Trust Research Grant F/00182/BI. Logistical support was provided in part by the Centre Français d’Etude Ethiopienne. We are particularly grateful to the people of the Hitoya and Tiyo districts, Arsi zone, Oromia region, for their warm welcome and for facilitating this research. We thank the field team for many months of hard work in the field on data collection. Suggestions provided by James Holland Jones, Aurelie Cailleau, and Sid Karunaratne are greatly appreciated. Finally, we thank the anonymous reviewers for their helpful comments and feedback.

Author information

Authors and Affiliations

Authors

Corresponding author

Correspondence to Lucie Clech.

Additional information

Publisher’s Note

Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Electronic supplementary material

ESM 1

(DOCX 29.9 kb)

ESM 2

(XLSX 65.3 kb)

Rights and permissions

Reprints and permissions

About this article

Check for updates. Verify currency and authenticity via CrossMark

Cite this article

Clech, L., Hazel, A. & Gibson, M.A. Does Kin-Selection Theory Help to Explain Support Networks among Farmers in South-Central Ethiopia?. Hum Nat 30, 422–447 (2019). https://doi.org/10.1007/s12110-019-09352-6

Download citation

  • Published:

  • Issue Date:

  • DOI: https://doi.org/10.1007/s12110-019-09352-6

Keywords

Navigation