Web edition: July 1, 2011
Print edition: July 16, 2011; Vol.180 #2 (p. 32)
August 4, 1928 | Vol. 14 | No. 382
Dinosaurs died of rickets
Thirty-five-ton dinosaurs, that languidly lived and loved in the slimy lagoons of the Mesozoic Age, some 135,000,000 years ago, probably disappeared off the earth because their supply of ultra-violet light was cut off by vast clouds of volcanic dust obscuring the face of the sun. And so the biggest brutes that ever walked became extinct from the action of rickets, universally known today as a malady of babies.
This is one of the newest theories of science to account for the disappearance of the dinosaurs, proposed by Dr. Harry T. Marshall, pathologist of the University of Virginia. Migrations, new enemies and the cold climatic changes brought about by the glaciers of an age of ice, along with the great reptiles’ own stupidity, great size, and sluggish habits, all helped the extinction along, but ultra-violet deficiency is felt by Dr. Marshall to be the main cause.
Lack of ultra-violet light and the anti-rachitic vitamin D bring about a disturbance of the mineral chemistry of the body that results in malformed bones. Deprived of sunlight, one of their necessary sources of vitality, and probably forced to eat strange foods as the changed climatic conditions fostered new types of plants, the great beasts gradually grew weaker and weaker. . .
“If the ancient types of animal were dependent upon the sun’s short rays,” explained Dr. Marshall, “ultra-violet deficiency should have been followed by rather rapid extinction.” —Marjorie MacDill
UPDATE | July 16, 2011
Throw theory a (malformed) bone
Without vitamin D, bony dinos such as Triceratops would have been toast.
It should go without saying that not all ideas are created equal. But even equally logical, intriguing and all-around plausible ideas don’t receive equal access to serious scientific investigation. What separates those that move forward from those that fall flat often comes down to one feature: falsifiability.
In 1928, Harry Marshall suggested that a lack of vitamin D, the result of increased volcanic activity and thus ash-laden skies, could lead to all sorts of troubles for the dinosaurs. Within a few generations, he said, malformed bones, vulnerable young, shifting food sources and digestive disturbances could wipe out the creatures entirely. While Marshall’s idea has some logic to it — particularly now that researchers think a meteorite hit Earth 65 million years ago, shrouding the planet in dust — it has been largely ignored.
The problem, says Kevin Padian of the University of California, Berkeley, is that like hundreds of other theories behind the dinosaurs’ demise, Marshall’s proposal isn’t testable. Even Marshall admitted: “Extinction produced in this manner should leave only slight traces in the fossil bed.” The best evidence that could ever be expected, he said, would be a bone with signs of rickets or a defective tooth.
That would be cool, Padian says. But even then, establishing a causal connection would be required. And researchers would need some proposals for which dinos would have been affected first, why and how — and then evidence for those hypotheses, too.
But just because an idea doesn’t deserve equal consideration right now doesn’t mean it should be scrapped entirely. Stalled theories are handy to have around. If the right bone ever arrives, scientists should be ready to shift gears and dig in. —Elizabeth Quill