A Fresh Perspective on T. rex Ancestry: Research Links Evolutionary Origins to Asia
In a revolutionary paleontological finding, an extensive study released on May 7, 2025, in Royal Society Open Science has redefined the evolutionary landscape of one of the most legendary and feared creatures in Earth’s past—Tyrannosaurus rex. Conducted by a global team from University College London (UCL), this research asserts that T. rex did not emerge exclusively in North America as was previously believed. Rather, its immediate ancestors probably migrated from Asia more than 70 million years ago, utilizing the Bering Land Bridge, thus transforming our comprehension of dinosaur distribution during the Late Cretaceous.
Exploring the Ancestry of Tyrannosaurus rex
The evolutionary path of T. rex has long intrigued paleontologists. The fossil evidence hinted at potential links between tyrannosaurs from North America and their counterparts in Asia, notably Tarbosaurus. Nevertheless, the exact nature of this connection remained ambiguous.
Chief author Cassius Morrison, a doctoral candidate in UCL’s Department of Earth Sciences, along with his team, employed sophisticated biogeographical and computational techniques to meticulously analyze the geographic and evolutionary trends of over 75 species of tyrannosaurs and megaraptors. The results indicated that the massive tyrannosaurid lineage that eventually led to T. rex likely migrated into North America from Asia more than 70 million years ago.
“Our findings support the notion that most giant tyrannosaurs, including T. rex, originated in Asia—their forebears crossed into North America via the Bering Land Bridge,” Morrison stated. This route is the same ancient land corridor that allowed early humans to move into the Americas.
This finding strengthens the evolutionary ties between T. rex and Asian tyrannosaurs like Tarbosaurus more decisively than previously recognized connections with North American relatives such as Daspletosaurus.
The Ascendance of Dinosaur Giants Tied to Climatic Changes
Aside from identifying T. rex’s geographic lineage, the study uncovered an unforeseen environmental catalyst for the gigantic size seen in dinosaurs. Approximately 92 million years ago, following the zenith of the Cretaceous Thermal Maximum, the Earth underwent a significant cooling phase. This worldwide climate transition coincided with a marked increase in body size among tyrannosaurids and their lesser-known relatives, the megaraptors.
Paleontologists theorize that cooler conditions might have prompted evolutionary adaptations, fostering features like warm-blooded metabolisms, insulating feathers, and larger body forms in these colossal predators. As apex carcharodontosaurid predators declined and eventually vanished during the same time frame, ecological spaces opened up for tyrannosaurids and megaraptors to rise as leading predators.
Key Findings of the Study:
– T. rex’s forebears are believed to have migrated from Asia to North America through the Bering Land Bridge around 70 million years ago.
– The Beringian migration aligns T. rex more closely with Asian species like Tarbosaurus rather than traditional North American dinosaurs such as Daspletosaurus.
– Climatic changes post-Cretaceous Thermal Maximum sparked the evolution of giant predators.
– Megaraptors were likely distributed more widely across the globe than previously acknowledged.
– The disappearance of competing predators (like carcharodontosaurids) facilitated the dominance in size of tyrannosaurs and megaraptors.
The Often Overlooked Megaraptors
While T. rex holds a significant position in science and popular culture, this study sheds new light on megaraptors—an agile, clawed predator family whose fossils have mainly been discovered in the Southern Hemisphere.
“Megaraptors showcase a different predation strategy compared to the bone-crushing tyrannosaurs,” explained Dr. Mauro Aranciaga Rolando from the Bernardino Rivadavia Natural Sciences Argentine Museum. “They depended on speed, agility, and formidable claws on well-formed arms—starkly different from T. rex’s reduced forelimbs.”
The team’s modeling suggests megaraptors may have occupied regions of ancient Gondwana beyond known fossil locations, possibly reaching into Europe and Africa. This enriches our understanding of their paleogeographic distribution, adding complexity—and depth—to our grasp of global dinosaur biodiversity.
Predators Adapted to Their Prey
The research further explored the ecological adaptations between these two predator groups. North America’s T. rex specialized in hunting relatively smaller yet heavily defended herbivores—like horned Triceratops and duck-billed hadrosaurs—utilizing a biting power unequaled by any known terrestrial carnivore.
In contrast, in the landscapes of Gondwana, megaraptors likely hunted young sauropods—the gargantuan long-necked dinosaurs that prevailed in southern ecosystems. This distinction in prey type significantly influenced the unique adaptations of each group: T. rex’s powerful bite and sturdy skull versus megaraptors’ nimble limbs and gripping arms.
“Our evolutionary models indicate that geography and prey availability played a significant role in shaping the anatomical specializations.”