What would happen if dinosaurs roamed the earth today? Originally appeared on Quora – the knowledge sharing network where compelling questions are answered by people with unique insights.
Answer by Ben Waggoner, Ph.D in Integrative Biology, paleontologist, and evolutionary biologist, on Quora:
Massive devastation of trendy Manhattan wine bars.
Okay, first of all, one subgroup of dinosaurs is still roaming the Earth today: the birds. So dinosaurs poop on your car, visit your feeders, and feed you well on Thanksgiving. But I assume you meant what would happen if the extinct, non-bird dinosaurs could somehow roam the Earth today.
That raises the point that different dinosaur species lived at different times and places. Tyrannosaurus never feasted on Stegosaurus, for example, because Steggy lived something like 100 million years before Rexy ever existed. Tyrannosaurus never got to taste Giraffatitan because they not only lived 80 million years apart, they lived on separate continents. (This is one of my beefs with Jurassic Park; Dilophosaurus, the critter that spit poison in Wayne Knight’s face, lived about 120 million years and 6000 miles away from Velociraptor, the critters that ate Bob Peck.) So if all the extinct dinosaurs suddenly started roaming the Earth together at the same time … well, you’d have utter ecological chaos, as the Velociraptors discovered that their tactics for hunting Protoceratops were ineffective against unfamiliar Ankylosaurus, and Triceratops found out that it had no idea how to dodge Allosaurus. You might as well turn some polar bears, bison, tree sloths, and kangaroos loose on the Serengeti plain.
But let’s keep it simple. Suppose we could magically transport a decent sample of the dinosaurs from one place and time into the present day. Let’s pick up a herd of duckbills—say, Edmontosaurus or Maiasaura —and a herd of Triceratops, a few smallish predators like Dakotaraptor, and a couple of Tyrannosaurus. All of these lived in the same general area (western North America) in the same general time frame (late Cretaceous). So we plop all of these down in North America today, and …
There were flowering plants in the Late Cretaceous, but they didn’t yet dominate the landscape. The typical landscape in Cretaceous North America seems to have been “fern savannas”—somewhat like prairies, but dominated by small ferns, not grasses—broken up by tracts of forests dominated by conifers, ginkgos, ferns, and cycads. There were flowering plants, including decent-sized trees, but again, nothing like the diversity we have now.
And here’s the problem: Modern flowering plants have had ~100 million years to evolve anti-herbivore defenses, and just to evolve complex chemistry in general. We don’t know enough about dinosaur biochemistry to know exactly what they would find poisonous. Suffice it to say that as soon as the herbivores started eating the local plants, they would be exposed to a whole range of chemicals that they had no adaptations to handle. They might not even have the sensory receptors to taste them.
The actual effects are anyone’s guess. The simplest case would be that the herbivores would get sick and die, like modern sheep or cows in the West that eat death camas or lupine. Some might end up tripping out, like humans eating ergot-infected rye or jimsonweed, or livestock eating Oxytropis or Astragalus “locoweeds”. Survivors might fail to lay viable eggs, or lay eggs that would hatch into deformed offspring—like sheep and goats eating false hellebore and giving birth to lambs and kids with cyclopia.
The carnivorous dinosaurs might have easy pickings for a while, as they feasted on dead or incapacitated herbivorous dinosaurs. This wouldn’t last long, though. Sooner or later, Tyrannosaurus rex has to find living prey, or possibly fresh carrion, depending on whether it was a predator or scavenger (that’s another story). There were mammals alive at the same time and place as T. rex, but none very big—and for all we know, modern mammal flesh might be unpalatable. But recall that birds belong within the dinosaurian clade. T. rex may run out of Triceratops to eat, but if it can find large, relatively slow birds to munch, it might survive for a while, assuming that it can run fast enough to catch them (a controversial question). A T. rex that was lucky enough to find a turkey farm would probably eat the birds like so much popcorn. The few ostrich ranches in the America West could find their business nipped in the bud, if by “nipped” you mean “messily dismembered.”
The herbivores would be equally hard to manage. Imagine: a herd of Triceratops eats a patch of Datura stramonium and promptly levels downtown Bismarck, North Dakota, hallucinating like a Grateful Dead show gone horribly wrong. Twitching, retching, slobbering duckbills collapse across I-94, blocking traffic into Fargo for hours, after getting into a patch of Apocynum cannabinum (hemp dogbane). A photo of a poor baby Edmontosaurus whose mamma tried hellebore, with a single eye and adorably deformed face, threatens to displace the “I Can Has Cheezburger?” cat as the most viral meme on the Internet …
And a herd of Maiasaura, starving and desperate, wanders into Manhattan and discovers a wine bar decorated with lush ferns and rare tropical cycads. Minutes later, the wine bar is flattened, its greenery devoured. Newly invigorated by their first decent meal in weeks, the Maiasaura rampage from one fern bar to the next. Hundreds of Wall Street middle-management flunkies who were hoping to score that night are severely inconvenienced.