How different would our world be if dinosaurs were alive today? The answer is: very.
13 Things That Could Happen If Dinosaurs Were Still Alive
Updated on Jul. 11, 2025
Well, for starters, they are
That’s right, dinosaurs do still exist, and they are everywhere, in the form of birds. That adorable little sparrow on your windowsill? Dinosaur. The noisy blue jay disturbing your morning coffee? Dinosaur. Pigeons, geese, hawks, you name it—they’re all descendants of large, two-legged, non-avian dinosaurs called theropods. Theropods, “whose members include the towering Tyrannosaurus rex and the smaller velociraptors,” according to Scientific American, adapted certain existing dino features (like feathers) into the birds we see today.
We wouldn’t recognize them
Say that species-extinction asteroid hadn’t hit Mexico 66 million years ago, and life on earth had continued apace. Well-known dinosaurs like the triceratops “would be totally different than anything we know from the fossil record,” science writer Riley Black writes in The Guardian. Why? They, too, would have continued to adapt. “There might even be new groups of dinosaurs that didn’t exist during the Mesozoic era. The present earth wouldn’t be a hodgepodge of old favorites, but an entirely different mix of unknown dinosaurs,” writes Black.
In fact, we may never see them at all
Why? It’s likely that, with a preponderance of dinosaurs remaining on our planet, humans and many other mammals would not have had the chance to evolve into existence. “Even though mammals thrived in the shadow of the dinosaurs, they did so at a small size,” says Black. “And even though the very first primates had evolved by the end of the dinosaurian reign, they had more in common with a tree shrew than with you or me … [Dinosaurs] would have undoubtedly continued to influence mammalian evolution.”
It would not look like Jurassic Park
The movie took a lot of liberties with the possible, writes biologist Ben Waggoner in Forbes. “Dilophosaurus, the critter that spat poison in Wayne Knight’s face, lived about 120 million years ago and 6,000 miles away from Velociraptor, the critter 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.”
Part of the chaos? Dead herbivores
Plant eaters like Edmontosaurus, snacking on the rich diversity of flowering plants that exist today, on and in our plains, prairies and forests, would likely have gotten sick, and perhaps even died, from this diet. At the very least, writes Waggoner, they might have just spent their whole lives hallucinating. The chemical makeup of modern plants isn’t anything like what dinosaur biology was meant to handle. Other, more palatable plants might have been completely decimated by the hungry (and huge) critters.
Happy times for carnivores!
All those dead and dying herbivores lying around—poisoned by flowering grasses and other plants their systems couldn’t handle—would have presented a total feeding bonanza for Tyrannosaurus rex, for example, as well as other scavenging predators, according to Forbes. Easy pickings!
But that bounty would have been short-lived
That’s because the dead animals would run out eventually. And when that happened, what would T. rex and friends eat? “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,” writes Waggoner. Also likely: “A T. rex that was lucky enough to find a turkey farm would probably eat the birds like so much popcorn.”
Climate change would mix things up …
“An event known as the Paleocene-Eocene Thermal Maximum, 55 million years ago, saw average global temperatures reach 8 degrees Celsius hotter than today, and rainforests spanning much of the planet,” according to BBC Future. “In this hothouse world with abundant vegetation, perhaps many long-necked sauropods might have grown more rapidly, breeding at a younger age and shrinking in size; several ‘dwarf’ sauropods (some little bigger than a cow) were already known from European islands in the late Cretaceous.”
… and so would fruit
Many modern birds have adapted to eating fruit and drinking the nectar of our numerous flowering plants—in fact, these things co-evolved so that birds would disperse the plants’ seeds. Some non-bird vegetarian dinosaurs could have developed this ability as well. Some or all may have grown into gradually smaller animals thanks to the relative ease of digestion of fruits and flowering plants compared with the gymnosperms of the Cretaceous, paleontologist Matt Bonnan told BBC Future.
They’d adapt to grasslands
In the absence of dinosaurs, mammals slowly evolved to have the ability to eat grassland plants. Vertebrate paleontologist Darren Naish speculated that surviving dinosaurs would have evolved much more quickly, thanks to evolutionary advantages they’d already developed, like the “batteries” of up to 1,000 teeth that hadrosaurs had in their jaws, which would have been extremely well suited to grinding grass.
Physical changes would occur …
… to the heads and bodies of these grass munchers as they evolve. As BBC Future points out, “Horses and cows have flattened muzzles useful for cropping tough, low-lying vegetation.” Grass-eating, duck-billed dinosaurs might have developed squared-off snouts, and “sauropod necks might have shortened to aid grazing at their feet.”
Dinos evolving to burrow?
“It’s odd that dinosaurs didn’t really [burrow], as it’s a common way of life among lizards and snakes,” paleontologist Paul Barrett told BBC Future. “Given more time, some dinosaurs might have become subterranean specialists—the scaly or feathery equivalent of mammalian moles,” the article notes.
They’d possibly be furry … but probably not cuddly
Some dinosaurs before the asteroid hit were living up above the Arctic Circle, in conditions that were considerably warmer than what was to come with various ice ages over the millennia. If dinosaurs were alive today, would they have developed “thick and elaborate pelts, covered in fuzz and feathers all the way down to the tips of their toes and tails?” Naish wonders. A woolly T. rex, perhaps?
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Sources:
- BBC: “What if dinosaurs hadn’t died out?”
- Forbes: “Here’s What It Would Be Like If Dinosaurs Were Around Today”
- The Guardian: “What if dinosaurs were still alive? You asked Google – here’s the answer”
- Scientific American: “How Dinosaurs Shrank and Became Birds”
- Riley Black, award-winning science writer and amateur paleontologist based in Salt Lake City
- Ben Waggoner, PhD, assistant professor of biology at the University of Central Arkansas
- Matt Bonnan, PhD, paleontologist and professor at Stockton University in New Jersey
- Darren Naish, British vertebrate paleontologist and author
- Paul Barrett, PhD, British vertebrate paleontologist at the Natural History Museum in London
