This post is by Jessica Fries-Gaither, a 2024-2025 Albert Einstein Distinguished Educator Fellow at the Library of Congress.
How do we know when an organism has gone extinct?
This feature from The Tacoma Times presents an intriguing story from paleontology—the history of the coelacanth (pronounced SEE-la-canth). The earliest fossils of this lobe-finned fish date back to the Devonian time period (approximately 420 million years ago). Coelacanth fossils are conspicuously absent after the Cretaceous Period (about 66 million years ago), and as the end of the Cretaceous was marked by the mass extinction event that killed off the dinosaurs, scientists believed that the fish also died out at this time.
As the story reports, a live coelacanth was caught off the coast of South Africa in December 1938, completely upending scientists’ understanding of the species. The coelacanth was dubbed a “living fossil,” a term first used by Charles Darwin in his 1859 book, On the Origin of Species, to describe organisms that appear to be relatively unchanged from their extinct fossil ancestors. While scientists today prefer not to use that term, it remains part of the popular lexicon—and can be an intriguing entry point into science concepts like evolution, extinction, and the nature of science.
Share the feature with students (you may wish to cover up the unrelated drawings that separate the headline from the article). Invite them both to examine the graphic elements and to read the brief text and then record their observations, reflections, and questions. Students will likely wonder about the term, “living fossil” and can conduct research to learn more about the term’s origin and history. You might also extend student thinking by posing questions of your own such as
- How do we know when something is extinct? Is there a way to know with 100% certainty?
- What does the term living fossil imply about the animal?
- How much (or how little) has a coelacanth evolved over time?
- How closely related are modern coelacanths to their ancient ancestors?
These questions, whether student-generated or teacher-prompted, can lead to further research about living fossils in general and, in particular, the coelacanth.
After students have researched and answered their questions, direct them back to the original newspaper feature. They will likely find the account to be lacking in both context and detail. Challenge students to write a more informative headline, or for a greater challenge, an entire article presenting information about the coelacanth scientifically.
Are you interested in other paleontology resources? Take a look at our newest Primary Source Set: Paleontology, Past and Present.
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