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By Hillel J. HoffmannPhotographs by Jonathan Blair



About 90 percent of all species vanished in a mysterious mass extinction 250 million years ago.



Read this compelling excerpt, or print the whole story.

“The Karoo is the kind of place where people fall asleep at the wheel,” said Roger Smith, a paleontologist at the South African Museum, as we drove across the treeless land. “But it may be the best place to see the terrestrial realm’s transition from the Permian to the Triassic period.”

We ascended through sheep-ranching country toward the Lootsberg Pass. The rocks that surrounded us date from the late Permian. For every yard of altitude we gained, we traveled tens of thousands of years forward in time, heading for the Permian’s conclusion.

If we had driven here before the extinction, we would have seen animals as abundant and diverse as those of today’s Serengeti, except most would have belonged to a group known as synapsids. Often called mammal-like reptiles—they looked like a cross between a dog and a lizard—the synapsids were Earth’s first great dynasty of land vertebrates.

“We’ve found fossils of many kinds of synapsids in these rocks, especially tortoise-beaked dicynodonts, which likely lived in herds and browsed on vegetation along the river banks,” said Smith. “There were also a lot of smaller grazers and root grubbers, like Diictodon, a dachshund-shaped dicynodont that probably dug up roots and shoots. They were preyed upon by gorgonopsians—fleet-footed synapsid carnivores with needle-sharp teeth.”

The late Permian rocks we passed as we neared Lootsberg Pass capture the synapsids at the height of their reign. For more than 60 million years they were Earth’s dominant land vertebrates, occupying the same ecological niches as their successors, the dinosaurs.

Smith slowed at a switchback, rolled down the window, and pointed to a horizontally banded cliff. “See that road cut?” he asked. “That’s your Permo-Triassic transition zone. Brace yourself, you’re about to go through the extinction.” The fossils embedded in this road cut suggest that synapsids took a savage hit at the end of the Permian.


Share your thoughts: Are humans causing another mass extinction?





In More to Explore the National Geographic Magazine team shares some of their best sources and other information. Special thanks to the Research Division.


The Permian Extinction was the greatest mass extinction ever, but it’s not the only big one. Five times in Earth’s history—at the end of the Ordovician (440 million years ago), the Devonian (370 m.y.a.), the Permian (250 m.y.a.), the Triassic (210 m.y.a.), and the Cretaceous (65 m.y.a.) periods—mysterious events wiped out more than half the species alive. Some researchers think that humans have put so much stress on the environment that we’re causing another mass extinction (see “The Sixth Extinction,” National Geographic Magazine, February 1999).


The Extinction Files
http://www.bbc.co.uk/education/darwin/exfiles/index.htm
A website associated with the BBC’s documentary series by the same name, it explores the Earth’s five great extinctions.

The Geological Society
http://www.geolsoc.org.uk/template.cfm?name=fbasalts
Many researchers think the world’s worst episode of flood basalts, a type of volcanic eruption, caused the Permian extinction. Learn more about these upwellings of gooey lava—and the ways they may have changed the course of the history of life.

Woodleigh, Carnarvon Basin, Western Australia: a new 120 km diameter impact structure
http://www.elsevier.nl/gej-ng/10/18/23/80/25/34/article.html
An asteroid impact has been blamed for the extinction that wiped out the dinosaurs. A few researchers think that an asteroid caused the Permian extinction as well, but no one had found an impact crater that could date to the end of the Permian period . . . until now.

The National Park Service
http://www.nps.gov/gumo/gumo/geology.htm
Want to see fossils of the Permian extinction’s victims? The marine animals that inhabited Permian reefs can be seen on scenic hikes in Texas’s Guadalupe Mountains National Park. This website describes the geology of the park’s ancient reefs.

Fossil Reptiles of the South Africa Karoo
http://www.museums.org.za/sam/resource/palaeo/cluver/index.html
The Karoo, a desert-like area in South Africa’s interior, is the best place in the world to see fossils of the Permian extinction’s most famous terrestrial victims, the synapsids. Here’s an electronic field guide to these odd-looking animals.

Backwoods Home Magazine
http://www.backwoodshome.com/articles/silveira57.html
The end of the world—it almost happened 250 million years ago. What are the chances that global disaster could strike again? A whimsical look at doomsday odds from Backwoods Home Magazine, which advocates self-reliant country living.


Broad, William J. “Newfound Crater Could Explain Worst Mass Extinction,” New York Times, April 25, 2000.

Erwin, Douglas H. The Great Paleozoic Crisis: Life and Death in the Permian. Columbia University Press, 1993.

Erwin, Douglas H. “The Mother of Mass Extinctions,” Scientific American, July 1996, 72-78.

Monastersky, Richard. “Life’s Closest Call: What Caused the Spectacular Extinctions at the End of the Permian Period?” Science News, Vol. 151, February 1, 1997, 74-75.

Mory, Arthur J. et al. “Woodleigh, Carnarvon Basin, Western Australia: A new 120 km diameter impact structure,” Earth and Planetary Science Letters (Elsevier), Vol. 177 (2000), 119-128. Available online at http://www.elsevier.com/locate/epsl.

Renne, Paul R. et al. “Synchrony and Causal Relations Between Permian-Triassic Boundary Crises and Siberian Flood Volcanism,” Science, 8 September 1995, Vol. 269, 1413-1416.

Smith, Roger. “Survivor of the Great Extinction,” MuseNews, Vol. 13, No. 6, June 1999. Available online at http://www.museums.org.za/sam/muse/9906.htm.


“Biodiversity Milestones.” National Geographic, Feb. 1999.

Morell, Virginia. “The Sixth Extinction.” National Geographic, Feb. 1999, 42-59.

“Tracking Life in Prehistoric Times.” National Geographic, March 1990.

Gore, Rick. “Extinctions.” National Geographic, June 1989, 663-699.

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