Skip to Content

Chimpanzee Droppings Lead Scientists to Evolutionary Discovery


Erica F. Kosal
Department of Biology
North Carolina State University


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.


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 Areas

Scientific method

Educational Level

High school, Undergraduate lower division



Type / Methods




Subject Headings

Biology (General)  |   Evolutionary Biology  |   Molecular Biology  |   Public Health  |   Epidemiology  |   Zoology  |  

Date Posted


Teaching Notes

Case teaching notes are password-protected and access to them is limited to paid subscribed instructors. To become a paid subscriber, begin the process by registering.

Teaching notes are intended to help teachers select and adopt a case. They typically include a summary of the case, teaching objectives, information about the intended audience, details about how the case may be taught, and a list of references and resources.

Supplemental Materials

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

  Click and Learn: Creating Phylogenetic Trees from DNA Sequences hhmi/
  Immunology Virtual Lab hhmi/

Answer Key

Answer keys for the cases in our collection are password-protected and access to them is limited to paid subscribed instructors. To become a paid subscriber, begin the process by registering.


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.