Imagine a world where you live alongside T. rex still roaming the forests, and herds of Triceratops grazing open plains alongside modern animals like deer or elephants.
It may sound like science fiction at first—but according to a recent study published in Current Biology, this scenario could very well have been reality, had a massive asteroid not struck Earth 66 million years ago.
For over three decades, scientists have debated a major question: Were dinosaurs already on the brink of extinction before the catastrophe? Or were they thriving in stable, diverse populations—until their fate was abruptly changed by an extraordinary, unavoidable event?
Fossil Records Can Be Misleading
For years, many scientists believed that dinosaurs were already in decline before the asteroid ended the Cretaceous period. Fossil data appeared to show a drop in both the number and diversity of dinosaur species beginning around 75 million years ago—long before the impact occurred.
However, a research team from University College London (UCL), led by Dr. Chris Dean, looked deeper into the data and found that this apparent decline may not reflect the real situation. Instead, they suggest that the perceived drop in dinosaur populations may be due to a decreased likelihood of fossil preservation and discovery during that time, particularly in North America.
Research Focus: Four Dinosaur Families
The study focused on four major dinosaur groups from North America:
- Ankylosauridae – armored herbivores like Ankylosaurus
- Ceratopsidae – three-horned herbivores like Triceratops
- Hadrosauridae – duck-billed dinosaurs like Edmontosaurus
- Tyrannosauridae – predators like Tyrannosaurus rex
More than 8,000 fossils from these groups were analyzed over an 18-million-year span leading up to the extinction event, specifically between 84 and 66 million years ago. This crucial period covers two key stages in geological history: the Campanian (83.6–72.1 million years ago) and the Maastrichtian (72.1–66 million years ago).
With such a large dataset, the researchers didn’t just rely on the number of fossils found—they also accounted for the likelihood of those fossils being discovered over time.
Mapping Ancient Life: A Methodology
To generate a more accurate picture, the team applied occupancy modeling—a statistical approach commonly used in modern ecological studies to estimate species distribution across a given area.
They divided North America into small grid cells based on geological, geographic, and ancient climate data, then mapped out the probable habitats of the four dinosaur groups.
The results were striking: there was no significant contraction in the regions likely to be inhabited by dinosaurs. In other words, their habitats remained wide and stable, showing no signs of an ongoing population collapse. What actually changed was our modern ability to detect their presence in the fossil record.
Why Dinosaur Fossils Are Scarce
This research emphasizes that the fossil record is not a perfect snapshot of the past. In the late Cretaceous period, particularly during the last six million years before the asteroid impact, many geological areas containing fossils became less exposed. Factors such as tectonic uplift, mountain formation, and the retreat of the sea gradually buried the rocks that held these historical records.
This explains why fossils from this period are so scarce—not because dinosaurs disappeared, but because their fossils became increasingly difficult to find.
Interestingly, only one group of dinosaurs was more abundant during this period: Ceratopsidae. This group was easier to detect because they tended to live in grassy plains far from riverbeds, exactly the type of environment that was better preserved in the geological record of that time.
Rewriting Dinosaur Extinction
Co-author Dr. Alessandro Chiarenza from UCL, who has long studied dinosaur diversity near the end of the Mesozoic era, stated that what appeared to be a decline in species diversity was likely the result of an increasingly narrow window of fossil sampling—not a true decrease in diversity.
Geological phenomena such as sea-level changes, tectonic activity, and land uplift have made it more difficult to discover fossils from that period.
The Dinosaurs' Final Days: Misjudged?
This research challenges the long-held assumption that dinosaurs were already on a path to extinction before the Chicxulub event—the massive asteroid impact that marked the end of the Cretaceous period. By taking into account the limitations of the fossil record and using more advanced analytical techniques, scientists have concluded that dinosaurs likely still had stable populations and habitats up until their final day.
In other words, if Earth had not experienced that extraordinary cosmic collision, we might still see Ankylosaurus roaming the forests or T. rex hunting on the open plains—sharing the world with humans, birds, and mammals.
