One Tyrannosaurus rex seems scary enough. Now picture 2.5 billion of them.
That is how many of the fierce dinosaur king probably roamed Earth over the course of a couple of million years, a new study has found.
Using calculations based on body size, sexual maturity and the creatures’ energy needs, a team at the University of California, Berkeley calculated how many T-rex lived over 127,000 generations.
Photo: Reuters
The study, published in Science on Thursday, presents a first-of-its-kind estimation, but has a margin of error the size of a T-rex.
“That’s a lot of jaws,” said University of California Museum of Paleontology director Charles Marshall, the study’s lead author. “That’s a lot of teeth. That’s a lot of claws.”
The species roamed North America for about 1.2 million to 3.6 million years, meaning that the T-rex population density was small at any one moment.
There would be about two in a place of the size of Washington DC, or 3,800 in California, the study said.
“Probably like a lot of people, I literally did a double take to make sure that my eyes had not deceived me when I first read that 2.5 billion T-rexes have ever lived,” said Kristi Curry Roger, a paleobiologist at Macalester College who was not part of the study.
The estimate helps scientists calculate the preservation rate of T-rex fossils and underscores how lucky the world is to know about them at all, Marshall said.
About 100 T-rex fossils have been found — 32 of them with enough material to determine that they were adults.
If there were 2.5 million T-rex instead of 2.5 billion, we would probably have never known they existed, Marshall said.
The researchers calculated the population by using a general biology rule of thumb that says that the bigger the animal, the less dense its population.
They added estimates of how much energy the carnivorous T rex needed to stay alive, which they think is somewhere between a Komodo dragon and a lion.
The more energy required, the less dense the population.
They also factored in that T-rex reached sexual maturity at about 14 to 17 years old and lived up to 28 years.
Given uncertainties in T-rex’s generation length, range and how long they roamed, the team said that the total population could be as little as 140 million or as much as 42 billion, with 2.4 billion as the middle value.
The science about the biggest land-living carnivores of all time is important, “but the truth, as I see it, is that this kind of thing is just very cool,” said James Farlow, a geologist at Purdue University.
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