Humans in our present form have existed for several hundred thousand years, which seems unimaginably long compared to the lifespan of one man. Even more astonishing is the fact that long before we appeared, Tyrannosaurus rex ran the site more than 10 times longer.
Now new research is trying to calculate exactly how many terrifying, thunderous lizards may have trampled and made their way across Earth over several million years. The result: probably a total of about 2.5 billion, but that number could actually be up to 42 billion.
That peak number is probably less than half the total number of people who have ever lived, but it’s still a lot of huge, hungry prehistoric predators, especially considering what a relatively rare finding of the T. rex fossil is for paleontologists.
“Today, there are about 32 relatively well-preserved post-juvenile T. rexa in public museums,” said Charles Marshall, director of the University of California Paleontological Museum. “Of all the adults after minors who have ever lived, that means we have about one in 80 million.”
Marshall led a study published in the latest issue of the journal Science that entered known data about extinct beasts into computer simulations to basically create educated assumptions about their total numbers.
The billions of tall beasts that have lived for millions of years are still a much lower population density than those of humans today, of course. The study estimates that the total population of T. rexes at any given time was probably about 20,000 adults. Clearly nothing compared to the nearly 8 billion human meat bags that are rolled today.
But Marshall and his colleagues at UC Berkeley estimate the population density of about one dinosaur every 39 square kilometers (100 square kilometers). This means that, statistically speaking, during the Late Cretaceous period, you could expect T. rex to be located about 11.3 kilometers from your place. Not a very safe environment for a lot of travel.
However, there is a lot of uncertainty in the estimates that Marshall and his team came up with. Although the simulation found 2.5 billion total T. rex as the best assumption, the exact figure could actually be somewhere in the wide range between 140 and 42 billion.
“In a way this was a paleontological exercise as far as we can know and how we know it,” Marshall said. “It’s amazing how much we actually know about these dinosaurs and, of that, how much more we can calculate. Our knowledge of T. rex has expanded so much in the last few decades thanks to more fossils, more ways to analyze them, and better ways to integrate information into more known fossils.” ”
The team is also opening up a source of computer codes used in the research, which they hope could allow paleontologists to estimate how many other species it may miss in the excavations.
“With these numbers, we can begin to estimate how many short-lived, geographically specialized species may be missing in fossil records,” he said. “This may be a way to start quantifying what we don’t know.”
One thing is for sure for at least one person: Putting quantity in the historical number of T. rexesa brings some nightmares into sharper focus.