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Chimpanzee Droppings Lead Scientists to Evolutionary Discovery


Erica F. Kosal
Department of Biology
North Carolina Wesleyan College


This interrupted case study focuses on the research of Dr. Beatrice Hahn, who investigates DNA sequences in chimpanzee droppings in order to explore the origins of the human immunodeficiency virus (HIV). Students first consider the types of data that can be gained through collecting chimpanzee feces and studying the behavior of these animals. Students then apply this information to learn more about microevolution when they compare DNA sequences. Finally, students learn about ELISA tests and consider the role of basic and applied science. This case study is appropriate for an introductory biology course for non-majors or majors.

  • Understand the difference between basic and applied science and realize the significance each contributes towards the field of science.
  • Get a sense of the kinds of studies and types of data that can be gathered in the field and gain practice with posing questions and hypotheses.
  • Understand how HIV could have evolved from SIV.
  • Understand that there are alternative hypotheses on the evolution of HIV, but that the most widely accepted hypothesis stems from the zoonosis of SIV to humans and the subsequent evolution into HIV.
  • Be familiar with how HIV is detected in humans.
  • Understand how two genetic sequences can be compared to reveal information about evolutionary relationships.
Keywords: Human immunodeficiency virus; HIV; simian immunodeficiency virus; SIV; retrovirus; primate; ape; chimpanzee; Pan troglodytes troglodyte; microevolution; evolution; selective pressure; antibodies; ELISA; DNA; RNA; zoonosis; infectious disease; pandemic
Topical Area: Scientific method
Educational Level: High school, Undergraduate lower division
Formats: PDF
Type/Method: Interrupted
Language: English
Subject Headings: Biology (General)   Evolutionary Biology   Molecular Biology   Public Health   Epidemiology   Zoology  
Date Posted: 04/16/08
Date Modified: N/A
Copyright: Copyright held by the National Center for Case Study Teaching in Science, University at Buffalo, State University of New York. Please see our usage guidelines, which outline our policy concerning permissible reproduction of this work.

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Supplemental Materials

The supplemental material below may be used with this case study:

  Click and Learn: Creating Phylogenetic Trees from DNA Sequences hhmi/
This 27-slide presentation explains how DNA sequences can be used to generate such trees, and how to interpret them. Produced by HHMI BioInteractive.
  Immunology Virtual Lab hhmi/
This virtual lab teaches the procedures of performing an ELISA test to determine whether a particular antibody is present in a patient's blood sample. Produced by HHMI BioInteractive.


The following video(s) are recommended for use in association with this case study.

  Origin of HIV hhmi/
Video clip of Dr. Beatrice Hahn discussing her research that has traced the origin of HIV to chimpanzees in Cameroon. Running time: 5:32 min. Produced by HHMI BioInteractive.

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