Could Dinosaurs Survived In Modern Times

Breathless and Cold

The world as it exists today is wildy different than it was in the Cretaceous, when many of our favorite dinosaurs lived. Perhaps the most immediate challenge facing any dinosaur living in the modern world would be getting enough oxygen.

The beginning of the age of dinosaurs, about 215 million years ago, corresponded with an increase in atmospheric oxygen from 15  percent to 19 percent. The current atmosphere has about 21 perfect oxygen so some of those early dinosaurs from the Triassic would likely be plenty comfortable running around today. Their friends from the Cretaceous wouldn't be so lucky. .

Over the course of the next 150 million years things continued to change such that the oxygen  requirements of late-Cretaceous dinosaurs might have been much higher.  Namely the T.rex and Velociraptor lived between 90 and 66 million years ago when the atmosphere on Earth was  positively stacked with oxygen.

Using air bubbles trapped in amber, scientists were able to analyze samples of the atmosphere during the Cretaceous and found oxygen levels as high as 35 percent. For a dinosaur like T.rex that had adapted to live in a world with that much oxygen, running around and chasing Bryce Dallas Howard  in the modern atmosphere would be like hunting prey while climbing Kilimanjaro. Each breath would offer barely more than half of the oxygen  they're used to. Moreover, that's a best-case scenario at sea level. If you live in Colorado, at a higher elevation where there's less oxygen, it's possible  your dinosaur pursuers would pass out before they ever reach you.

They'd also be fighting the cold, at least from their perspective. Global temperatures during the Cretaceous were between 5 and 10 degrees warmer than they are today and the difference in temperature by latitude was less extreme.

All told, any dinosaurs let loose on the modern world would find themselves inhabiting a planet which looks not at all like the one the left behind, making every moment unpleasant at the very least. Maybe that's  why they're so angry.