If you were to travel back to when dinosaurs walked the Earth, it might take you a little while before realizing that you had slipped into another time. A wandering Tyrannosaurus or a shovel-beaked Edmontosuarus chewing a rotting log would be immediate giveaways, of course, but the forests, floodplains and other landscapes of the time would not be so alien as to immediately arouse your suspicion. We still inhabit the same planet as our favorite saurians, after all, and the world of the dinosaurs was not quite like what we often see in the movies.
The trick almost every dinosaur movie tries to perform is how to bring us in contact with the terrible lizards. Sometimes the creatures live on a lost world—a plateau or island where the Age of Reptiles never ended. Jurassic Park popularized another method: genetic reinvention, returning dinosaurs to the world they supposedly ruled. Time travel is another favorite, either bringing the scaly stars to the present or throwing humans back into the past. The latest prehistoric romp, 65, in theaters this weekend, attempts something a little different, with future humans seeming to drift through both space and time to crash land on Earth just before the Cretaceous come to a fiery close.
First thing’s first—the title 65 is a dino-sized mistake. In 2012 the International Commission for Stratigraphy, or geologists who determine Earth’s timescales, revised the end of the Cretaceous Period to be about 66 million years ago rather than the previous estimate of 65.5. If you were to visit Earth about 65 million years ago, during a time called the Paleocene, you would find thick forests where the descendants of mammals that survived the asteroid impact were starting to get big. Triceratops would have been extinct for a million years.
But when did accuracy ever stop Hollywood? From the trailers released so far, 65 follows the struggle of a pilot (Adam Driver) and a child (Ariana Greenblatt) as they stumble through Cretaceous forests and past ancient geysers as they’re chased by Tyrannosaurus, Velociraptor-like carnivores and other prehistoric terrors. The question the movie invites viewers to entertain while munching on their popcorn like an enthusiastic Edmontosaurus munches on leaves is how humans could survive in a forest primeval inhabited by creatures that could gobble us up in two bites. Before considering a stroll through the Late Cretaceous forest, or to the theater, you should know a few things.
We have a relatively incomplete view of the Late Cretaceous world. That’s because the fossil and geologic records are uneven, preserved in some places but not others. Much of what paleontologists have studied comes from places where sediment was being laid down—like sand in oceans or silt carried by streams. Still, all the individual pieces help outline the bigger picture. “If a time traveler should be lost in the latest Cretaceous of North America,” says Alfio Alessandro Chiarenza, a paleontologist with the University of Vigo in Spain, they would see “lush tropical forests covering the lowlands to an abundance of streams running through them from nearby mountains.” The range wouldn’t look like it does today, but would be lower and still be in the process of being pushed up.
“The Late Cretaceous Earth would be a mixture of familiar and unfamiliar,” says Caleb Brown, a paleontologist with the Royal Tyrrell Museum in Canada. Despite the impression that the Late Cretaceous was the peak of the “Age of Dinosaurs,” the great reptiles wouldn’t necessarily be around every other tree. “The iconic dinosaurs would be rare on the landscape,” Brown says, “so you would likely see many more turtles, frogs, birds and lizards cross your path before you stumbled into a lumbering ankylosaur or tyrannosaur.”
Even the arrangement of the Earth itself would look like an altered version of what we now know. What we’d eventually name North America, Africa, Australia and Antarctica would all have recognizable outlines. Still, plenty of notable differences existed 66 million years ago. India was an island continent, sitting near prehistoric Madagascar, and Australia was still connected to Antarctica. The Americas wouldn’t touch for tens of millions of years, and what’s now Europe was largely an archipelago flooded by shallow seas. The world was warmer than it is now, with an average summer temperature of about 82 degrees, but ice had once again begun to build at the poles. Earth was still very much a greenhouse world, with high levels of carbon dioxide in the atmosphere but relatively lower amounts of oxygen than today. A time-traveling human would be able to breathe without difficulty, even lacking the specialized air sacs that allowed dinosaurs to breathe more efficiently than any mammal.
The obligatory presence of T. rex in 65 indicates that the story unfolds in what’s now western North America, one of the areas of the Cretaceous world we’ve come to know quite well. The lowlands where the tyrant dinosaur stalked might have resembled parts of the modern Gulf Coast, with forests of conifers growing among swampy habitats dotted with ancient relatives of willows, magnolias and sassafras. You wouldn’t find fields of grass, though. Vast, grassy plains only spread about 36 million years later, so much of the low-growing groundcover of the Late Cretaceous was ferns, cycads and similar plants. For that reason, many production companies often shoot their prehistoric films in places like British Columbia, where mossy forests of redwoods at least approximate the Cretaceous look.
Many of the perils a Cretaceous traveler would face would be familiar to anyone who’s stumbled through the backcountry or gone camping far away from roads and fire pits. Thunderstorms and heavy rains would likely pose a problem. Chiarenza notes that a time traveler would have to contend with fierce seasonal storms not unlike those seen in the southeastern United States each hurricane season. And, much like these hot and humid areas now, biting insects would likely present a hassle, too. The scene might recall someplace in Florida, wet and buzzing with bugs. Turtles, crocodile relatives, birds, lizards, fish and small mammals would be everywhere. Still, sooner or later you’d see a dinosaur and realize that you’d traveled far from 2023.
Small dinosaurs lived in the Late Cretaceous, including carnivores such as Acheroraptor. But the average dinosaur would be much larger, an animal closer to three tons. Most of these were herbivores such as Edmontosaurus and Triceratops, great plant eaters that changed their habitats through where they walked and what they ate. In one area of the Late Cretaceous Hell Creek Formation in Montana, for example, about 40 percent of the fossils found were attributed to Triceratops. The infamous T. rex was still fairly common—about 24 percent of the sample—but still significantly scarcer than any of the plant-eating species. And those herbivores were far from harmless. We know from damaged bones that Triceratops fought each other with their impressive horns, and injuries sustained by visitors who try to get too close to bison at our modern national parks are a reminder of how dangerous herbivores can be.
Almost certainly mysteries and dangers existed in the Late Cretaceous of North America that we don’t know yet. “We know only a small fraction of extinct animals due to the vagaries of fossil preservation,” Chiarenza says. “An unexpected predator, or a big, dangerous kind of horned dinosaur, might represent a physical threat to anyone wandering this terra incognita.” We know practically nothing of dinosaurs in upland, more mountainous habitats, and so anyone who wandered upslope would start encountering organisms paleontologists have never seen.
Of course, the question hanging over all of 65 is whether the inhabitants of the Cretaceous world would chase down a human morsel just for the novelty of it. We’ll never know the answer for certain. But given the behavior or large carnivores, T. rex would probably not stalk a human given how much energy would be required for a relatively lean payoff. Paleontologists have estimated that an adult T. rex would need about 200,000 calories a day, or roughly an adult human and a half. Raptors probably wouldn’t be too enticed, either, as their curved claws evolved to pin down modest morsels like mammals and smaller dinosaurs rather than taking on big prey.
Sorry, Adam Driver, but to a T. rex, at least, you’re not really a snack.
Editors' Note, March 22, 2023: Due to a math error this article misstated the daily caloric intake of a T. rex. It should be 200,000 calories a day, not 2,500 calories a day.