An abundance of vegetation during the late Jurassic Period drove the enormous size of herbivorous Apatosauruses like the one illustrated.
ROGER HARRIS/SCIENCE PHOTO LIBRARY/getty images
When the Earth Was Green
Riley Black
St. Martin’s Press, $29
Imagine being a paleontologist exploring Utah’s Jurassic-aged rocks. Imagine discovering the bones of a 20-meter-long, 20-ton herbivorous dinosaur. Then consider: How could any beast become so big? The answer, according to science writer and paleontologist Riley Black, lies in plants.
Black narrates the story of this Jurassic saurian in a chapter of her latest book, When the Earth Was Green. The imagined Apatosaurus lumbers through lush cycads, ferns and conifers, vacuuming plant matter into her digestive system of “enormous fermentation vats,” which allows her to extract maximal nutrients. The abundance of verdant foliage available for the adult Apatosaurus to inhale drove its species’s gigantic size. Black even conjures the green pats of dung produced by the (probably) gassy animal as it farts along.
With a focus firmly on plants, Black masterfully uses science to breathe life into ancient worlds in which some of our favorite prehistoric animals lived. Each chapter — written as a vignette with its own appendix explaining the science behind Black’s story choices — portrays a particular time and place.
Take the first chapter, set in Arctic Canada 1.2 billion years ago. This is a world of no forests, no fish, no seashells. Bare rock studded with snowcapped mountains presided over sediment-filled oceans stocked with mats of cyanobacteria and other mostly unicellular organisms. Against this backdrop, Black describes something that’s not quite plant. It’s a multicellular, photosynthesizing red alga. “It’s only in this moment that what were once single cells are beginning to combine and coalesce into new and unexpected arrangements,” she writes. We wouldn’t be here without this evolutionary step.
This red alga and its photosynthetic brethren are ancestors of the first plants that crept onto land, inadvertently luring critters out of the ocean. “It was the plants, not fleshy-finned fish, that changed the world when they came ashore,” Black writes.
Paleontology is often framed as stories of colonization and conquest — life colonized land, dinosaurs dominated the Mesozoic Era. Black rejects this framework, instead twining tales of communities into an “evolutionary romance.” She reminds us that “we did not arrive here on our own, but as part of an ongoing relationship with the botanical.” By itself, a dinosaur is just a dinosaur. Farting sauropods dining at the salad bars of Jurassic forests, warming the planet with their methane-rich malodors, is something else entirely.
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