Coryphodon, one of the first large mammals, on display as part of the AMNH's Extreme Mammals exhibit.
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Photo by Brian Switek.
Coryphodon, one of the first large mammals, on display as part of the AMNH's Extreme Mammals exhibit.

One for the Beasts

I like dinosaurs. A lot. Their bones were what first inspired me to start asking questions about the past and, many years later, set me on a path of professionally puzzling over prehistory. But I can’t give all the credit to fantastic saurians.

Mammals have always been part of my ancient education, even when they were shadows of the Cenozoic that I overlooked in favor of Apatosaurus and company. Plastic effigies of Uintatherium were stashed inside plastic bags of scaly monsters I got from the supermarket toy aisle, elephants trussed up as shaggy mammoths tromped through the movies I’d stay up late to watch, and no museum visit was complete without stopping to gaze at the bizarre bones of the giant ground sloths. I feel sorry that I didn’t fully appreciate them earlier. They’re both strange and familiar – animals that are perhaps easier to envision, but difficult to truly understand.

Not that mammals were restricted to the time after the non-avian dinosaurs were ushered off the evolutionary stage. The first mammals evolved over 220 million years ago, back when crocodile cousins were in the limelight and dinosaurs were marginal players. And while mammals stayed small as dinosaurs rose to dominance, the beasts nevertheless took on an array of ecological roles that included swimmers, burrowers, gliders, and more. The catastrophic finale of the Cretaceous is what let the surviving mammals go from understudies to leads, and many of them were as spectacular as any dinosaur.

That’s what makes the present so frustrating. The world is still populated by a wonderful assortment of mammals, but, as paleontologist Jessica Theodor notes in the Dinologue video below, extinction has removed some of the stars. In the deserts and alpine forests around my Utah home, for example, I should still be able to find elephants, camels, ground sloths, sabercats, and more. But I can’t. These communities, which had been evolving for tens of millions of years, were stripped down within the last 8,000 years by natural and human-caused triggers that are still hotly debated by specialists.

We shouldn’t forget these mammals and their forebears. Understanding the mammals of the past, and how they responded to phenomena such as rapid climate change, may help us get at least a rough sketch of what may happen in the future. Their old bones record how life responds to alterations and fluctuations, and what held true for fossil mammals may provide clues about the fate of living species. Fossil beasts aren’t dead history, Theodor reminds us. They’re an essential part of the continuing story of life: