‘Mass Extinction’ vivifies the science of die-offs

Documentary explores causes of dinosaur disappearance, ‘Great Dying’

cliffs in Spain

These rocks in Spain helped geologists determine what killed the dinosaurs.

© HHMI J.B. Spector/Museum of Science and Industry

Mass Extinction: Life on the Brink
Premieres November 30
Smithsonian Channel

Anyone with a passing interest in dinosaurs knows that the beasts were killed off some 65 million years ago after a colossal asteroid struck Earth. But what many people probably don’t know is how paleontologists came to that conclusion. Mass Extinction: Life at the Brink tells that story.

The hour-long documentary, airing on the Smithsonian Channel, explores the causes of two of Earth’s five mass extinctions: the dinosaurs’ demise and the “Great Dying.” That long-ago extinction, roughly 252 million years ago, saw as many as 97 percent of species on Earth disappear. By focusing on how researchers have pieced together these ancient whodunits, Mass Extinction offers great insight into how science works.

The film begins with a journey back in time — to the 1970s. Geologist Walter Alvarez is studying rocks in Italy. An odd sliver of clay in a stretch of limestone intrigues him: It contains an unusually high concentration of iridium, an element that is normally rare in Earth’s crust. Similar iridium-rich layers appear elsewhere around the world and all date to around the time of the dinosaur extinction. Working with his Nobel Prize–winning physicist father, Luis, Alvarez hypothesizes that the iridium came from an asteroid. The documentary goes on to show how subsequent studies over the last few decades have uncovered remnants of the asteroid’s gigantic crater and have calculated the extent of the space rock’s destruction.

The gray layer, found in rocks in Spain and elsewhere, marks the dinosaur extinction event. © HHMI
Alien forces aren’t always at play in mass extinctions. In the case of the Great Dying, the destruction was homegrown. The world just before the extinction event was very different from today’s, as the program’s CGI effects illustrate. Earth’s landmasses made up one giant supercontinent called Pangaea,armored trilobites ruled the seas and reptiles resembling the demon dogs from Ghostbusters ruled on land.

Researchers suspect that the creatures were wiped out by a major episode of climate change triggered by an enormous volcanic eruption in Siberia. Pinning the blame on the volcano requires getting the timing just right: Did the volcano erupt before, during or after the die-off? The film shows researchers working in Siberia and China trying to answer that question. Increasingly, these scientists say, the evidence is pointing to the volcano as the culprit.

The last third of the documentary shifts to the present and examines whether Earth is on the brink of a sixth mass extinction. And here the film falls a bit flat. The filmmakers cram so much into a mere 15 minutes — evidence that we’re on track for a mass die-off, proof that humans are responsible and actions people should take to stave it off — that their arguments feel incomplete. That’s especially the case when compared with the film’s thoughtful treatment of the other two extinctions.

But on balance, the documentary is an informative introduction to the science of mass extinctions. The film explains the research so that anyone can follow along while still managing to captivate viewers who are well-versed in science.

Erin Wayman is the managing editor for print and longform content at Science News. She has a master’s degree in biological anthropology from the University of California, Davis and a master’s degree in science writing from Johns Hopkins University.

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