Dinosaurs Would Still Roam Earth If Asteroid Hadn’t Hit, Study Says - GreekReporter.com (2025)

Dinosaurs may have survived and continued to roam the planet Earth if a massive asteroid had not struck Earth 66 million years ago, says a new study.

Researchers say the extinction was sudden and not the result of a long-term decline, challenging a theory that the species was already struggling before the impact.

Fossil evidence shows no clear sign of population drop

For years, many paleontologists believed dinosaurs were already struggling during the final stretch of the Cretaceous period. A drop in species variety and fewer fossil discoveries from that era were often cited as signs of slow extinction.

New research, published Monday in Current Biology, suggests this theory may be built on flawed evidence.

Researchers from University College London analyzed nearly 8,000 dinosaur fossils from North America, focusing on two key time frames: the Campanian (84 to 72 million years ago) and the Maastrichtian (72 to 66 million years ago).

The team studied four major dinosaur groups, including horned, armored, duck-billed, and large carnivorous species.

No environmental cause found for apparent decline

While the fossil record appears to show a dip in diversity during the last six million years before the asteroid impact, scientists found no clear environmental changes that would explain such a decline.

Instead, they say the data likely reflects gaps in fossil preservation and accessibility, not an actual drop in dinosaur populations.

“It’s been a subject of debate for more than 30 years—were dinosaurs doomed and already on their way out before the asteroid hit?” said Chris Dean, lead author of the study and a paleontologist at University College London.

He explained that the findings suggest they were doing just fine until that sudden catastrophic event.

Geological changes likely disrupted fossilization

The study highlights several geological shifts that may have interfered with fossil formation. Approximately 75 million years ago, the Western Interior Seaway—a vast inland sea that once divided North America—began to retreat. Simultaneously, the Rocky Mountains began to rise. These changes likely disrupted the conditions needed for fossilization, particularly in regions where many dinosaur species once roamed.

In addition, rock layers from the Maastrichtian period are often buried under vegetation or remain unexposed, making fossil recovery more difficult. Since half of the known fossils from this time come from North America, the findings could have global implications.

Horned dinosaurs were preserved more than others

Among the fossils studied, horned dinosaurs like Triceratops—known as Ceratopsians—were the most frequently preserved. These species lived in open plains, which were more favorable for fossilization.

In contrast, duck-billed dinosaurs, or Hadrosaurians, preferred riverbanks. Reduced river flow during this time may have limited sediment buildup, making fossil preservation less likely.

Study suggests asteroid impact caused a sudden extinction

“Dinosaurs were probably not inevitably doomed to extinction at the end of the Mesozoic [252 million to 66 million years ago],” said co-author Alfio Alessandro Chiarenza. “If it weren’t for that asteroid, they might still share this planet with mammals, lizards, and their surviving descendants: birds.”

What you see here is an asteroid crater 😳

The Chicxulub crater was formed around 66 million years ago, when a large asteroid (10km in diameter) struck the Earth. Many scientists think that this event was the cause of the the Cretaceous-Paleogene extinction. pic.twitter.com/i1LlMxJnms

— Curiosity (@MAstronomers) October 28, 2022

The findings shed new light on one of paleontology’s most debated questions and suggest that the dinosaurs’ disappearance from Earth was not part of a slow, inevitable decline but rather the result of an extraordinary, rapid disaster from the asteroid.