• Schacht, R, KL Kramer, T Szekely and P Kappeler, eds (2017) Adult Sex Ratios and Reproductive Strategies: A Critical Re-examination of Sex Differences in Human and Animal societies. Philosophical Transactions, B 372 (1729) ISSN 0962-8436. Published, 07/2017.
  • Kramer, KL, R Schacht & A Bell (2017) Adult sex ratios & partner scarcity among hunter-gatherers: implications for dispersal patterns and the evolution of human sociality. Philosophical Transactions of the Royal Society, B 372 20160316 Published, 07/2017.
  • Schacht, R, KL Kramer, T Székely & P Kappeler (2017) Adult sex ratios and reproductive decisions: a critical reexamination of sex differences in human and animal societies. Philosophical Transactions, B 372 20160309 Published, 07/2017.
  • AV Jaeggi*, KL Kramer*, R Hames*, EJ Kiely, C Gomes, H Kaplan & M Gurven (2017) Human grooming in comparative perspective: People in six small-scale societies groom less but socialize just as much as expected for a typical primate. American Journal of Physical Anthropology DOI: 10.1002/ajpa.23164. * authors contributed equally to this work. Published, 01/18/2017.
  • Veile, A & KL Kramer (2016) Childhood body size is positively associated with cesarean birth in Yucatec Maya subsistence farmers. American Journal of Human Biology, Oct 4, 2016. DOI: 10.1002/ajhb.22920. Published, 10/04/2016.
  • Lancelotti, C, D Zurro, NJ Whitehouse, KL Kramer, M Madella, JJ García-Granero, RD Greaves (2016) Resilience of small-scale societies’ livelihoods: a framework for studying the transition from food gathering to food production. Ecology & Society 21(4):8. DOI: /10.5751/ES-08757-210408. Published, 10/2016.
  • Schacht, R & KL Kramer (2016) Patterns of family formation in response to sex ratio. PLoS ONE 11(8): e0160320. doi:10.1371/journal.pone.0160320. Published, 08/24/2016.
  • Codding, BF & KL Kramer, eds (2016) Why Forage? Hunters and Gatherers Living in the 21st Century. School of Advanced Research, Santa Fe. Published, 05/31/2016.
  • Kramer, KL & B Codding (2016) Hunter-Gatherers in the 21st century. In Why Forage? Hunters and Gatherers Living in the 21st Century, B Codding & KL Kramer (eds). School of Advanced Research & UNM Press, Albuquerque. Published, 05/01/2016.
  • Kramer, KL & RD Greaves (2016) Diversity or Replace. What happens to wild foods when cultigens are introduced into hunter-gatherer diets. In Why Forage? Hunters and Gatherers Living in the 21st Century, B Codding & KL Kramer (eds). School of Advanced Research & UNM Press, Albuquerque. Published, 05/01/2016.
  • Kramer, KL, A Veile & E Otárola-Castillo (2016) Sibling competition, growth tradeoffs. Biological vs. statistical significance. PLoS ONE 11(3): e0150126. doi:10.1371/journal.pone.0150126. Published, 03/03/2016.
  • E Cashdan, Kramer, KL, HE Davis, RD Greaves & L Padilla (2016) Mobility and navigation among the Yucatec Maya. Sex differences reflect parental investment, not mating competition. Human Nature 27:35-50. Published, 01/2016.
  • Blake, PR, K McAuliffe, T Callaghan, J Corbit, O Barry, A Bowie, L Kleutsch, KL Kramer, E Ross, H Vongsachang, R Wrangham, & F Warneken (2015) The ontogeny of fairness in seven cultures cultures. Nature 528:258-261. Published, 10/01/2015.
  • Kramer, KL & E Otárola-Castillo (2015) When mothers need others. Life history transitions associated with the evolution of cooperative breeding. Journal of Human Evolution 84:16-24. Published, 05/2015.
  • Kramer, KL & AF Russell (2015) Was monogamy a key step on the hominin road? Reevaluation of the Monogamy Hypothesis. Evolutionary Anthropology 24:73-83. Published, 03/2015.
  • Kramer, KL (2015) Cooperative breeding & human evolution. In Emerging Trends in the Social and Behavioral Sciences, RA Scott & SM Kosslyn (eds). John Wiley and Sons, Hoboken, NJ. DOI:10.1002/9781118900772.etrds0055. Published, 01/01/2015.
  • Kramer, KL and AF Russell (2014) Kin-selected cooperation without lifetime monogamy: human insights and animal implications. Trends in Ecology & Evolution 29(11):600-606. Published, 11/01/2014.
  • Greaves, RD and KL Kramer (2013) Hunter-gatherer use of wild plants and domesticates: archaeological implications for mixed economies before agricultural intensification. Journal of Archaeological Science 41:263-271. Published, 09/2013.
  • Kramer, KL (2014) Why what juveniles do matters in the evolution of cooperative breeding. Human Nature, special edition on eusociality, 25(1):49-65. Published, 06/2013.
  • Veile, A, J Winking, RD Greaves, M Gurven & KL Kramer (2012) Infant growth and the thymus: data from two South American native societies. American Journal of Human Biology 24(6):768-775. Published, 01/2012.
  • Kramer, KL (2011) The evolution of human parental care and recruitment of juvenile help. Trends in Ecology and Evolution 26(10):533-540. Published, 10/2011.
  • Kramer, KL & PT Ellison (2010) Pooled energy budgets: Resituating human energy allocation tradeoffs. Evolutionary Anthropology 19:136-147. Published, 10/2010.
  • Kramer, KL (2010) Cooperative breeding and its significance to the demographic success of humans. Annual Review of Anthropology 39:414-436. Published, 10/2010.
  • Kramer, KL & JB Lancaster (2010) Teen motherhood in cross-cultural perspective. Annals of Human Biology 37(5):613-628. Published, 10/2010.
  • Kramer, KL, RD Greaves & PT Ellison (2009) Early reproductive maturity among Pumé foragers. Implications of a pooled energy model to fast life histories. American Journal of Human Biology 21(4): 430-437. Published, 10/2009.
  • Kramer, KL (2008) Early sexual maturity among Pumé foragers of Venezuela: Fitness implications of teen motherhood. American Journal of Physical Anthropology 136 (3): 338-350. Published, 05/2008.
  • Kramer, KL (2005) Maya Children: Helpers at the Farm. Harvard University Press, Cambridge. Published, 05/2005.

Research Keywords

  • life history, cooperation, cooperative breeding, evolution of childhood, behavioral ecology, hunter-gatherers

Research Groups

  • The Effects of Social Networks on Inequality , Other. Santa Fe Institute. 08/2016 - present.
  • Polygyny Paradox Project , Other. 01/2014 - present.
  • Dynamics of Wealth Inequality , Other. Santa Fe Institute. 02/01/2012 - present.

Grants, Contracts & Research Gifts

  • Currently funded research: Emerging Differences in Children’s Economic Roles and Parental Investment though the Fertility Transition of Maya Farmers. PI: Kramer. National Science Foundation, 08/01/2010 - present. Total project budget to date: $270,898.00
  • Risk Sensitive Decision Making among Maya Farmers: Subsistence diversification in Response to Novel Environments. PI: KL Kramer. Co-PI(s): R Schacht. National Science Foundation,, 07/01/2016 - 07/01/2019. Total project budget to date: $324,431.00
  • Spatial Reasoning among Maya Children: An Interdisciplinary and Cross-Cultural Study. PI: KL Kramer. University of Utah Interdisciplinary Research Pilot Program , 08/01/2015 - 07/31/2016. Total project budget to date: $10,000.00

Geographical Regions of Interest

  • Americas
    Mexico, South America, Madagascar & Small-scale societies everywhere.