The mighty Tyrannosaurus rex, long considered the apex predator of North America, may have originated from Asia before making its mark on prehistoric landscapes across the continent. According to a new study led by Cassius Morrison, a paleontology doctoral student at University College London, ancestors of the T. rex likely journeyed across a land bridge that once connected Asia and North America around 70 million years ago.
This latest research adds weight to the ongoing debate about the origins of one of history’s most iconic dinosaurs. By using advanced mathematical modeling, Morrison and his team traced the likely migration of tyrannosaurids — the group that includes T. rex — across the ancient Bering Strait from Siberia to Alaska during the late Cretaceous period.
Morrison explained that, back then, the region resembled today’s temperate rainforests of British Columbia, creating an environment where these fearsome carnivores could thrive. Tyrannosaurids, though dominant predators, were outnumbered by the plant-eating dinosaurs they hunted, making their fossils far less common and challenging to uncover in the present day.
To overcome gaps in the fossil record, the team used models combining existing fossil data, evolutionary family trees, and environmental conditions. Their findings indicate that more undiscovered fossils of T. rex ancestors could still be hidden in Asia, waiting for future paleontological discoveries.
One major revelation from the study is that tyrannosaurids experienced a rapid increase in body size as the planet cooled, possibly aided by insulating feathers or warm-blooded physiology. This growth surge coincided with the extinction of another group of giant predators, the carcharodontosaurids, roughly 90 million years ago. With their rivals gone, tyrannosaurids rose to the top of the food chain, eventually producing behemoths like T. rex, which weighed as much as 9 metric tons — comparable to a large elephant or a light tank.
Study coauthor Charlie Scherer noted that this extinction event “likely removed the ecological barrier that prevented tyrannosaurs from growing to such sizes.” The result was the rise of the largest tyrannosaurs in both North and South America by the end of the Cretaceous period.
Paleontologist Steve Brusatte, who was not involved in the study, praised the work for its detailed analysis of how tyrannosaurs and other predators evolved alongside changing climates. He remarked that even the most dominant dinosaurs were shaped by environmental factors, with cooler temperatures providing an advantage for bigger bodies.
Ultimately, the new findings suggest that the rule of the T. rex in North America was the result not just of fierce competition, but also of migration, extinction, and shifts in the prehistoric climate — painting a more dynamic portrait of dinosaur evolution than ever before.
