Study finds modern hunter-gathers relocateto maximize foraging efficiency6 March 2017

Batek residential mobility, Sept. 1975-June 1976. ABatek nuclear family prepares to move to the next camp.Credit: Kirk Endicott.

As bumblebees forage for nectar from one flowerto the next, at a certain point, they will move toanother area once their search for food becomestoo inefficient. This behavior, also observed amongother animals, conforms to a prevalent model inbiology called the "marginal value theorem." In likemanner, groups of modern hunter-gatherersrelocate their camps to maximize their foragingefficiency, according to a Dartmouth studypublished in the online Early Edition of the Proceedings of the National Academy of Sciences.The findings illustrate for the first time that themarginal value theorem also predicts campmovements among humans, specifically, amongthe Batek, a group of indigenous hunter-gatherersfrom Peninsular Malaysia.

"Our results support what many anthropologistshave long suspected - that hunter-gatherers

relocate their camps in response to how fast theydeplete local resources. This study provides newinsight about how our hominin ancestors mighthave moved as groups across ancient landscapes,"says lead author Vivek V. Venkataraman, a postdoctoral researcher in the department of human evolutionary biology at Harvard University,who was a graduate student in biological sciencesat Dartmouth at the time of the study.

The Batek are a socially egalitarian society whoformerly lived nomadically in the tropical rainforestsof north-central Peninsular Malaysia. Based ondata from a 1975-1976 study by culturalanthropologists Kirk and Karen Endicott, Dartmouthresearchers analyzed the relocation patterns ofBatek living in the Upper Lebir River watershed for93 days as they sequentially occupied 11residential camps, staying for an average of 8.2days at each camp. Men generally hunted smallgame and women gathered wild yams and fruit. Inaddition, the men also collected rattan (climbingpalm) vines and traded it for rice.

To test the predictions of the marginal valuetheorem, the researchers measured how muchfood the Batek acquired over time in camps, andpredicted when the Batek should move based onhow quickly they depleted local resources. A closematch was found between the predictions of themarginal value model and the actual camprelocation times. They typically relocated to anothercamp before completely depleting local resources.Even though the Batek lived in complex socialgroups, they managed to maximize their foragingefficiency as a group, perhaps, due in part to theirextensive social cooperation and food sharing.Camp movement decisions were discussed andmade collectively.

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The focal group of Batek foragers occupied 11 campsalong the Upper Lebir River in the state of Kelantan,Peninsular Malaysia. Credit: Thomas Overly.

Although the Batek often said that their decisions tomove were based on women's foraging forcarbohydrates (often tubers), the data revealedotherwise, as rattan turned out to be a moreaccurate predictor of how long the Batek stayed ata camp. Venkataraman and his colleagues suggestthat the Batek case illustrates how genderinequalities may be introduced into hunter-gathersocieties through access to agriculturalcarbohydrates, such as rice, which alters traditionalgendered divisions of labor.

"In the 1970s, Karen and I had the rare opportunityto live with a group of fully nomadic Batek foragershow became enthusiastic partners in our efforts torecord their acquisition of food and rattan, and theirfood sharing practices. We are delighted that ourtalented young colleagues, coming fromevolutionary biology, have been able to use someof the data we collected back then to addressimportant questions in hunter-gatherer studies,including the determinants of camp movements,"says Kirk Endicott, professor emeritus ofanthropology at Dartmouth.

In addition to Venkataraman and Endicott, ThomasKraft, a postdoctoral researcher at the University ofCalifornia Santa Barbara, who was a graduatestudent in ecology and evolutionary biology atDartmouth at the time of the study, and Nathaniel J.Dominy, professor of anthropology and adjunctprofessor of biological sciences at Dartmouth, whospecializes in evolutionary biology, also served asco-authors of the study.

To understand how the Batek way of life as hunter-gatherers is changing in the 21st century,Venkataraman and Kraft are conducting a broaderlongitudinal study using data collected across 34years by the Endicotts, in combination with theirown fieldwork in 2013, 2014 and 2016. They haveconstructed a genealogy of more than 1,000 Batekspanning 115 years, and hope to gain insights intohuman evolution by studying how human socialstructure and organization in small-scale societiesvary across time and space.

More information: Hunter-gatherer residentialmobility and the marginal value of rainforestpatches, Proceedings of the National Academy ofSciences. DOI: 10.1073/pnas.1617542114

Provided by Dartmouth College

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APA citation: Study finds modern hunter-gathers relocate to maximize foraging efficiency (2017, March6) retrieved 5 January 2022 from https://phys.org/news/2017-03-dartmouth-modern-hunter-gathers-relocate-maximize.html

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