50 years ago, the dinosaurs’ demise was still a mystery 

Excerpt from the July 22, 1972 issue of Science News

an illustration of a dinosaur skeleton partly buried by debris

Fifty years ago, scientists thought dinosaurs’ warm blood or soft eggs may have caused the reptiles to die out (illustration of a partially buried dinosaur skeleton shown). Now, mounting evidence points to a killer asteroid impact.

MARK GARLICK/Science Photo Library/Getty Images

July 22, 1972 issue of Science News

What did in the dinosaurs: Warm blood or soft eggs?Science News, July 22, 1972

Dinosaurs might have been endothermic, or warm-blooded…. The combination of large size, endothermy and naked skin may explain the extinction of dinosaurs. About 65 million years ago there was a sharp drop in temperature…. Dinosaurs, lacking skin insulation and too large to burrow underground … could not survive. Meanwhile, evidence has come that … the shells [of their eggs] became progressively thinner … too fragile to support the growing embryo.


Some dinosaurs may have been warm-blooded and some could have laid soft-shelled eggs (SN: 7/12/14, p. 6). But neither trait led to the reptiles’ demise. In the late 1970s, geologists proposed that an asteroid strike triggered a mass extinction (1/25/92, p. 56), killing more than 75 percent of life on Earth. That theory is now widely accepted. Scientists have even found the killer’s calling card: a crater about 180 kilometers wide on the coast of the Yucatán Peninsula in Mexico. The asteroid probably crash landed there in the springtime 66 million years ago, fossils hint (SN: 3/26/22, p. 8).

Maria Temming

Previously the staff writer for physical sciences at Science News, Maria Temming is the assistant editor at Science News Explores. She has bachelor's degrees in physics and English, and a master's in science writing.

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