About the Authors

Margaret A. Stanton

mastanton@gwu.edu

Affiliations Department of Biology, Georgetown University, Washington, D.C., United States of America, Department of Anthropology, The George Washington University, Washington, D.C., United States of America

Janet Mann

Affiliations Department of Biology, Georgetown University, Washington, D.C., United States of America, Department of Psychology, Georgetown University, Washington, D.C., United States of America

Competing Interests

The National Geographic Society Committee for Research and Exploration provided some funding for long-term field research. This does not alter the authors’ adherence to all the PLOS ONE policies on sharing data and materials.

Author Contributions

Conceived and designed the experiments: MAS JM. Performed the experiments: MAS JM. Analyzed the data: MAS. Contributed reagents/materials/analysis tools: MAS JM. Wrote the paper: MAS JM.