Academic journal article The Science Teacher

Experimenting with Extinction: A Multi-Disciplinary Investigation into Ancient Cat Extinctions

Academic journal article The Science Teacher

Experimenting with Extinction: A Multi-Disciplinary Investigation into Ancient Cat Extinctions

Article excerpt

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Imagine looking out your window and witnessing a pride of saber-toothed cats stalking their prey of giant ground sloths taller than a school bus. While these species may seem as ancient as dinosaurs, they went extinct only about 11,000 years ago at the end of the Pleistocene epoch (Barnosky et al. 2004). In fact, humans lived alongside such giant animals, or megafauna, for thousands of years. Megafauna are model organisms for teaching about ecology, anatomy, ancient Earth, evolution, or even predator-prey dynamics. High school students seem especially fascinated by saber-toothed cats, dire wolves, and armadillo-like animals the size of cars.

This article describes a lesson in which high school biology, ecology, environmental science, anatomy, and physiology students can devise hypotheses and test them with scientific data, identify unanswered questions, and design an additional study to answer those questions. This module connects students with exciting research and current science standards (see box, p. 55) and asks them to communicate their data. It also identifies extension opportunities appropriate for biology, anatomy, ecology, and environmental science courses.

Background

Living species have two options: evolve or go extinct. Numerous studies (e.g., Graham et al. 2016) examine why large herbivores such as giant mammoths went extinct. Less is understood about the extinction of top predators such as saber-toothed cats and American lions (larger than modern-day lions; Anyonge 1993). Extinct carnivorans may have been desperately scavenging carcasses and bones right before dying off, indicating a dramatic decline in prey or competition with humans for prey (Van Valkenbergh and Hertel 1993). However, more recent examinations of their tooth surfaces suggested that the large cats were not surviving on carcasses before their extinction (DeSantis et al. 2012). The cougar survived the extinction event, scavenging carcasses both in the past and today. Its "less picky" eating may have been key to its survival during the Pleistocene (DeSantis and Haupt 2014).

The investigation

Part 1: The hook and hypothesis formulation

Teachers first "hook" students via a short video (see "On the web") on the charismatic creatures of the Pleistocene. The introductory video provides background information on the megafaunal research and how fossils were used for study. Instead of, or in addition to, watching the video, students can research the questions listed in Figure 1 before the first lesson as homework. In-class discussion of these questions sets the stage for the remaining activities.

After the discussion, teachers divide students into groups of 2-4, attempting to group students with different abilities (e.g., artistic, quantitative, writing). Each group receives tooth breakage data from one of the video's featured scientists (Figure 2). Within their groups, students discuss these data and determine a hypothesis regarding the feeding behavior of extinct carnivorans. Groups plot their data (Figure 3, p. 52), define hypotheses, and then discuss their results with the rest of the class.

Students should clearly see that extinct carnivorans have a higher percentage of broken teeth than surviving carnivorans. Ultimately, the class should reach a testable Hypothesis 1: Saber-toothed cats and American lions actively scavenged on carcasses when living during the late Pleistocene. If Hypothesis 1 is upheld, this suggests that a prey reduction (possibly due to competition with humans) may have resulted in their ultimate extinction. Students may make an alternative hypothesis: Ancient cats, especially the American lion, underwent significant damage to their teeth from hunting larger prey. We don't test this alternate hypothesis, but it comes up in future discussions (see Part 2).

FIGURE 1
Examples of questions for an opening discussion. … 
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