READY, FIRE, AIM: How Many T. Rexes Were There?

The University of California at Berkeley has a reputation for existing somewhere outside the realm of reality.

That reputation may have been enhanced slightly this month, when the internet started sharing claims made by paleontology professor Charles Marshall that he and his students had calculated how many Tyrannosaurus Rexes had roamed the earth, back in the day.

You can read the official UC Berkeley article here, on the school’s website. From that article:

Marshall, director of the University of California Museum of Paleontology, the Philip Sandford Boone Chair in Paleontology and a UC Berkeley professor of integrative biology and of earth and planetary science, was also surprised that such a calculation was possible.
 
“The project just started off as a lark, in a way,” he said. “When I hold a fossil in my hand, I can’t help wondering at the improbability that this very beast was alive millions of years ago, and here I am holding part of its skeleton — it seems so improbable. The question just kept popping into my head, ‘Just how improbable is it? Is it one in a thousand, one in a million, one in a billion?’ And then I began to realize that maybe we can actually estimate how many were alive, and thus, that I could answer that question.”

Paleontologists have a special fondness for T. rex — don’t we all? — partly because so many fossils have been uncovered, beginning in 1874, when a T. rex tooth was found near Golden, Colorado.

For a long time, only a few pieces of the big guy’s skeletons were dug up — a leg bone here, a neck bone there — so scientists had to be inventive with their ideas about how big, exactly, T. rex was, and what he looked like. (Why T. rex left little pieces of himself scattered here and there, is still unclear.)

Eventually, some nearly complete skeletons were dug up, including ‘Sue’ — excavated in 1990 and named for amateur paleontologist Sue Hendrickson. ‘Sue’ is about 85% complete. (The skeleton, I mean.)

Another nearly complete T. rex, “Stan” (also named after an amateur paleontologist) had apparent lived a rough life. The fossilized bones suggested broken (and healed) ribs, a broken (and healed) neck, and a substantial hole in the back of its head, about the size of a Tyrannosaurus tooth.

But regardless of any broken ribs and cracked skulls, Professor Marshall and his students decided to calculate how many T. rexes might have been walking around (in a bad mood?) on an average Sunday afternoon during the Cretaceous Period, 68 million years ago. Which strikes me as incredibly ambitious, when you think about all the trouble the US Census had last year, just counting Americans who are actually alive and able to complete a convenient online form.

Basically, the team defined the Tyrant’s probable hunting grounds (about 900,000 square miles, all in North America)… and then looked at the ‘territory’ occupied existing, present-day meat-eating animals — lions, tigers and so on — and then multiplied by a certain number, based on T. rex’s height and weight and dietary preferences… including the sensible theory that the big guy probably subscribed to a Paleo diet.

Marshall is quick to point out that the uncertainties in the estimates are large. While the population of T. rexes was most likely 20,000 adults at any give time, the 95% confidence range — the population range within which there’s a 95% chance that the real number lies — is from 1,300 to 328,000 individuals. Thus, the total number of individuals that existed over the lifetime of the species could have been anywhere from 140 million to 42 billion.

So far, scientist have dug up about 30 skeletons. Sometimes they find just a tooth, and announce it as “another Tyrannosaurus Rex”.

The UC Berkeley scientists mined the scientific literature and the expertise of colleagues for data they used to estimate that the likely age at sexual maturity of a T. rex was 15.5 years; its maximum lifespan was probably into its late 20s; and its average body mass as an adult — its so-called ecological body mass — was about 5.2 tons…

I’m not sure how “5.2 tons” supposedly aligns with a Paleo diet… but then, I’m not a scientist.

Here’s an imaginative illustration of a Tyrannosaurs Rex, in a bad mood.

I truly love scientists, because they are so… so innocent. And so gullible. They dig up 30 partial skeletons — plus an occasional tooth, or maybe a knuckle — and head off into the conceptual ozone, describing the sexual activities and lifestyle of an animal that, as best they can tell, has been extinct for 60 million years.

Does this research have any bearing, whatsoever, on reality? Or did the professor and his students waste weeks of their lives playing a silly intellectual game?

We can find some solace, I suppose, in the fact that college students engaged in this type of activity are helping to keep America’s banks and financial institutions happy and solvent. From Forbes magazine:

The latest student loan debt statistics for 2020 show how serious the student loan debt crisis has become for borrowers across all demographics and age groups. There are 45 million borrowers who collectively owe nearly $1.6 trillion in student loan debt in the US. Student loan debt is now the second highest consumer debt category – behind only mortgage debt – and higher than both credit cards and auto loans.

When I was a child, I owned a plastic Tyrannosaurus Rex. It was purple, and had its mouth conveniently open so it could bite the other plastic dinosaurs. (No dinosaurs were actually harmed, however. The biting was done playfully.)

I would be curious how many purple, plastic T. rexes were manufactured by that company during the past 40 years. I suppose that number could be calculated.

If any college professors are interested.

Louis Cannon

Louis Cannon

Underrated writer Louis Cannon grew up in the vast American West, although his ex-wife, given the slightest opportunity, will deny that he ever grew up at all.