A cast of a T. rex skeleton on display outside the UC Museum of Paleontology at the University of California, Berkeley. The original, a nearly complete skeleton excavated in the badlands of Eastern Montana in 1990, is at the Museum of the Rockies in Bozeman, Montana.
Keegan Houser, UC Berkeley
Humans in our current form may have existed for several hundred thousand years, which seems an unimaginably long term compared to the lifespan of a single human. Even more amazing is the fact that long before we emerged, the Tyrannosaurus rex roamed more than 10 times as long.
Now, a new study is trying to calculate exactly how many of the terrifying, thundering lizards have stomped and gnawed across the Earth over the course of a few million years. The result: probably about 2.5 billion in total, but the number could even reach 42 billion.
That high number is probably less than half the total number of people who ever lived, but it’s still a lot of huge, hungry prehistoric predators, especially when we consider what a relatively rare find T. rex fossils are to paleontologists.
“There are about 32 relatively well-preserved, post-juvenile T. rexes in public museums today,” Charles Marshall, director of the University of California Museum of Paleontology, said in a statement. “Of all post-juvenile adults who have ever lived, this means we have about one in 80 million.”
Marshall led the study, published in the latest issue of the journal Science, which fed known data about the extinct beasts into computer simulations to make essentially educated guesses about their total numbers.
Of course, billions of towering carnivores that live for a few million years still have a much lower population density than that of humans. The study estimates that the total population of T. rexes was likely around 20,000 adults at any one time. Obviously nothing compared to the nearly 8 billion human meat bags hanging around today.
But Marshall and his colleagues at UC Berkeley estimate a population density of about one dinosaur per 100 square kilometers. That means that statistically during the late Cretaceous period, you could have expected a T. rex to be within about 7 miles of your location. Not exactly a safe environment to travel a lot.
However, there are many uncertainties in the estimates that Marshall and his team have come up with. While the simulation found a total of 2.5 billion T. rexes as the best estimate, the correct figure could be anywhere in a wide range between 140 million and 42 billion.
“In some ways this has been a paleontological exercise in how much we can know, and how we should know,” Marshall said. “It’s surprising how much we actually know about these dinosaurs and, from that, how much more we can calculate. integrate the many known fossils. ”
The team is also open-sourcing the computer code used in the study, hoping paleontologists can estimate how many other species may be missed in excavations.
“With these numbers, we can begin to estimate how many short-lived, geographically specialized species we might be missing from the fossil record,” he said. “This could be a way to start quantifying what we don’t know.”
One thing is certain for at least one person: by adding a quantity to the historical T. rexes count, certain nightmares are brought into sharper focus.