How many T rexes were there?
Over approximately 2.5 million years, North America likely hosted 2.5 billion Tyrannosaurus rexes, a minuscule proportion of which have been dug up and studied by paleontologists, according to a UC Berkeley study. University of CaliforniaHow many T. rexes were there? Billions.
Updated 7:54 PM ET, Thu April 15, 2021
CNN's Kristen Rogers contributed to this story.
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18 April, 2021 - 08:10pm
WASHINGTON (Reuters) - If one Tyrannosaurus rex - the school bus-sized meat-eating dinosaur that stalked the Cretaceous Period landscape - seems impressive, how about 2.5 billion of them?
Researchers on Thursday unveiled the first calculation of the total T. rex population during the estimated 2.4 million years that this fearsome species inhabited western North America during the twilight of the age of dinosaurs.
They considered factors including the size of its geographic range, its body mass, growth pattern, age at sexual maturity, life expectancy, duration of a single generation and the total time that T. rex existed before extinction 66 million years ago. They also heeded a doctrine called Damuth's law linking population to body mass: the bigger the animal, the fewer the individuals.
Their analysis put the total number of T. rex individuals that ever existed at about 2.5 billion, including approximately 20,000 adults alive at any one time.
Fossils of more than 40 T. rex individuals have been found since it was first described in 1905, providing a wealth of information about a beast that thrives in the popular imagination.
"Why iconic?" asked paleontologist Charles Marshall, who led the study published in the journal Science.
"Heck, a hugely massive killer with super-huge teeth, one that you would never dream up on your own if we didn't have the fossil record. So not only super-cool and beyond the imagination, but real. Like Godzilla, but actually real. And I think we like feeling small, and T. rex sure makes us feel small and vulnerable," Marshall said.
It was among the largest carnivorous dinosaurs, possessing a skull about 5 feet (1.5 meters) long, massive and muscular jaws with a bite force capable of crushing bone, a mouthful of banana-sized serrated teeth, a keen sense of smell, strong legs and puny arms with hands boasting just two fingers.
Perhaps the largest-known T. rex is a specimen named Sue at the Field Museum in Chicago, measuring 40-1/2-foot-long (12.3-meters), weighing an estimated 9 tons and living about 33 years.
The new study put the weight of the average adult T. rex at 5.2 tons, average lifespan at 28 years, generation time at 19 years, total number of generations of the species at about 125,000, and its geographic range at roughly 890,000 square miles (2.3 million square kilometers).
They calculated an average population density of about one T. rex for every roughly 40 square miles (100 square kilometers).
T. rex fossils have been found in Canada's Alberta and Saskatchewan provinces and the U.S. states of Montana, Wyoming, South Dakota, North Dakota, Utah, Colorado, New Mexico and Texas. T. rex apparently met a fiery end when an asteroid slammed into Mexico, exterminating three quarters of Earth's species.
While the uncertainties in the estimates were large and some of the assumptions may be challenged by other paleontologists, the study was a worthwhile effort to expand the understanding of this famous dinosaur, said Marshall, director of the University of California Museum of Paleontology and a University of California, Berkeley professor of integrative biology.
The formula could be applied to other extinct animals, Marshall added.
Paleontologist and study co-author Ashley Poust of the San Diego Natural History Museum said while 2.5 billion is a lot, it represents only about a third of Earth's current human population - and 20,000 is merely the size of a small town.
"They'd have to meet up over possibly long distances to mate, or maybe even care for their young," Poust said of Tyrannosaurus. "The numbers can seem big and cold, but I guess I see them as a pretty intimate window into their lives."
(Reporting by Will Dunham, Editing by Rosalba O'Brien)
One Tyrannosaurus rex seems scary enough. Using calculations based on body size, sexual maturity and the creatures' energy needs, a team at the University of California, Berkeley figured out just how many T. rex lived over 127,000 generations, according to a study in Thursday’s journal Science. It’s a first-of-its-kind number, but just an estimate with a margin of error that is the size of a T. rex. The species roamed North America for about 1.2 million to 3.6 million years, meaning the T. rex population density was small at any one moment.
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For the first time, scientists have estimated how many Tyrannosaurus rex, the so-called king of dinosaurs, once roamed the Earth. Why it matters: The number is staggering: 2.5 billion Tyrannosaurus rex lived and died during the roughly 2.4 million years the species survived on the planet, according to a new study set to be published in the journal Science on Friday.Stay on top of the latest market trends and economic insights with Axios Markets. Subscribe for freeThe study may help contextualize the fossil record and the rarity of finding certain fossilized prehistoric organisms, according to lead researcher Charles Marshall, director of the University of California Museum of Paleontology."I mean, to me, it's just amazing we could have come up with a number," Marshall told Axios. "Some people have asked me, 'How does your number compare to other numbers of the total that have ever lived?' The answer is it doesn't because there weren't any."How it works: The team of researchers couldn't use the limited fossil record to estimate the species' population, so they instead used Damuth’s Law, which describes a relationship between population density and body mass.The relationship, used in population ecology, generally states that species with larger body sizes tend to have lower population densities.The researchers then computed the average body mass of a T. rex, settling on a mean of 5,200 kilograms (roughly 11,460 pounds).Using the body mass, the team calculated that the species had a population density of around one individual per 40 square miles.By the numbers: With this information and an estimated geographic area that the species occupied, the researchers were able to approximate that about 20,000 T. rex were alive at any given time that the species lived on the planet.To find the total number of T. rex that walked the Earth, the team multiplied the species' standing population by the number of generations it spanned (around 127,000), which they determined by dividing how long the species survived by its estimated generation time of 19 years.The researchers noted that their estimated population density for the species would translate to roughly 3,800 T. rex in an area the size of California and just two in an area the size of Washington, D.C.Yes, but: Marshall said the precision of the analysis was "low" and this was primarily due to uncertainty about the accuracy of the relationship between living animals' body mass and their population density, rather than the paleontological data the team used.James Clark, a professor of biology at George Washington University who did not participate in the study, said the research didn't reach a definitive conclusion but showed the difficulties of estimating the lives of extinct animals."It's an exercise in what you can and can't tell," Clark said. "It gives you the chance to say, 'Wow, there really were a lot of these things, and we're not getting a lot of them captured in the fossil record.'"Go deeper: How the meteor that killed dinosaurs created modern forestsLike this article? Get more from Axios and subscribe to Axios Markets for free.
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Here's how many T. rex once roamed Earth, according to a team of researchers. The answer is staggering
18 April, 2021 - 08:10pm
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Billions of Tyrannosaurus rex roamed North America during their fascinating reign as top predators, according to a team of researchers that went about the daunting task of making the calculation.
Paleontologists from the University of California, Berkeley, set out to put a number on how many T. rex lived during the Cretaceous period — about 65 million to 98 million years ago — knowing that it wouldn't be a simple task.
Fossils have long been used to deepen our understanding about extinct creatures such as dinosaurs, but experts say it can be challenging to use these remains to calculate population density and abundance.
"There is just no information to make the estimate," explained Charles Marshall, director of the University of California Museum of Paleontology, who was part of the research team. "If you find an Easter egg in your garden, how can you estimate how many Easter eggs that have ever existed? It simply can't be done. You need information from somewhere else -- for example, the density of Easter eggs, the area over which eggs might be found, and for how many years Easter eggs have been placed in gardens."
"Previously researchers have tried to estimate things like the likely home range size of Tyrannosaurus, and its basic energetic needs, so this is a neat extension of previous work, and it includes lots of updated information on Tyrannosaurus," said Nizar Ibrahim, paleontologist at the University of Portsmouth (UK) and National Geographic Explorer, who was not part of the research.
"We just have to keep in mind that all of these intriguing studies come with a certain dose of uncertainty — there is just so much we still don't know about dinosaurs, even a Hollywood star like T. rex," Ibrahim added in an email.
Using the fossil record, density data and data from climate models, the UC Berkeley team calculated that roughly 20,000 adult T. rex, which lived throughout North America, probably existed at any one time. This, the researchers say in a study published in the journal Science, means that some 2.5 billion of the predators lived and died over the approximately 2.5 million years during which the dinosaurs lived.
For the first time, the team also calculated the longevity of the dinosaur: Using scientific literature and expert opinion, they estimated that the likely age of sexual maturity for a T. rex was 15.5 years, and its lifespan could reach into the late 20s. The dinosaur's average adult body mass was around 5,200 kilograms (11,464 pounds), and a growth spurt at sexual maturity could send them to 7,000 kilograms (15,432 pounds).
From these estimates, the team came to the conclusion that each generation of T. rex lasted for around 19 years, with there being one dinosaur for every 100 square kilometers (38.6 miles).
With a standing population of 20,000 of the dinosaurs, and with some 127,000 generations of the species, there would be 2.5 billion dinosaurs overall, the team determined.
The researchers' methods "seem to be very informative while also showing the present limits of what can be done with what we now know," said Jason C. Poole, head fossil preparator at Bighorn Basin Paleontological Institute and a paleontological artist, who was not part of the study.
"I am sure it will open doors for getting even better focus on the questions of population density and what that means over time," Poole added in an email. "So really this could help understand things like change in a species over time as it relates to evolution and changing ecosystems."
The study authors estimate that the population density of the species equated to 3,800 of the carnivorous dinosaurs in an area the size of California — but only two in an area the size of Washington DC.
Meanwhile, the results also allowed the report authors to determine that only about 1 in 80 million T. rex are preserved as fossilized remains.
"The great impact of this study may be that it shows just how rare fossils are, in that they only represent a small fraction of the individual organisms that existed not to mention depth of time as in how much happens in a few thousand to a million years," Poole said.
"In some ways, this has been a paleontological exercise in how much we can know, and how we go about knowing it," said Marshall, a study coauthor and UC Berkeley professor of integrative biology and of Earth and planetary science, in a statement.
"It's surprising how much we actually know about these dinosaurs and, from that, how much more we can compute. Our knowledge of T. rex has expanded so greatly in the past few decades thanks to more fossils, more ways of analyzing them and better ways of integrating information over the multiple fossils known," he said.
Ibrahim sees other possibilities stemming from this study.
"There are a lot of things we don't know about the physiology, behavior and feeding ecology of Tyrannosaurus, but this study offers an interesting approach to estimating the abundance and preservation rate of dinosaurs, he said.
"I would love to see it applied to other dinosaurs known from abundant fossils. Looking at a wider range of dinosaurs — predators and prey — might enable us to better compare dinosaur-age animal communities to modern ones.
"But we are just scratching the surface, and even with this intriguing study, there is still a long way to go before we can confidently apply such approaches more broadly to the study of dinosaurs."
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18 April, 2021 - 08:10pm
If you hear the word “dinosaur,” there’s a good chance that an image of a Tyrannosaurus rex flashes in your mind. That’s a credit to the incredible intimidation factor that the animals possessed, but it’s especially impressive when you consider that only around 50 T. rex skeletons have ever been found. Dinosaur fossils are obviously very rare, and it can be very difficult to get an idea of how many of any given animal actually existed on Earth. Now, a study focused on T. rex fossils offers an estimate for the number of these dinosaurs that have existed on Earth, and it’s a very big number.
Looking at the number of T. rexes that we know about and extrapolating information about their general locations, range, and length of time they existed on Earth, researchers writing in Science suggest there may have been literally billions of the animals over the course of their existence. Yeah, it’s a lot.
Estimating the abundance of a species is a common practice for extant species and can reveal many aspects of its ecology, evolution, and threat level. Estimating abundance for species that are extinct, especially those long extinct, is a much trickier endeavor. Marshall et al. used a relationship established between body size and population density in extant species to estimate traits such as density, distribution, total biomass, and species persistence for one of the best-known dinosaurs, Tyrannosaurus rex, revealing previously hidden aspects of its population ecology.
There’s a lot of math involved in estimating the population of any given animal at any time in history. For the T. rex research, the team used a number of data points including correlations between body mass and population density to offer an estimate of the number of these animals alive at any given time. The researchers figure this number to be in the neighborhood of around 20,000 post-juvenile T. rexes.
Then, by stretching that number out over approximately 127,000 generations and you come up with a very rough bottom-end estimate of around 2.5 billion adult T. rexes in the history of our planet. That’s a very big number, but the actual number of the creatures might actually be much larger than that. The researchers say that if you relax the data a bit to get a top-end estimate, you come up with something around 42 billion, or roughly 17 times the lower estimate.
To put this in comparison, the most accurate estimates we have about the number of humans to ever walk the Earth lands at around 107 billion. It’s pretty wild to think that number of T. rexes that walked the Earth could approach the halfway point in the number of humans that ever lived. Granted, the dinosaurs lived for over 125,000 generations and humans have only existed for less than 8,000 generations, but the total lifetime population comparisons are startlingly similar.
18 April, 2021 - 08:10pm
18 April, 2021 - 08:10pm
Billions of the giant Tyrannosaurus rex dinosaur existed during the species' millions of years of existence, although not all at once. Scientists estimate that about 2.5 billion of the giant dinosaur king roamed North America throughout the species' 2.4 million years of existence. That means the population density of the T. rex was not great, but there were enough for humans to know they existed over 65 million years after dinosaurs went extinct.
Researchers at the University of California, Berkley came to the 2.5 billion number using calculations based on body size, sexual maturity, and the Tyrannosaurus rex's energy needs. They estimated that the dinosaurs lived over 127,000 generations and published their findings in the journal Science. "That’s a lot of jaws," Charles Marshall, the study's lead author and the director of the University of California Museum of Paleontology, told the Associated Press. "That's a lot of teeth. That's a lot of claws."
The T. rex species lived in North America for 1.2 million to 3.6 million years, so scientists believe that the population density was very low at any one time. Although the 2.5 billion number sounds enormous, Marshall explained that the estimate is a testament to how lucky we are to know about them today. Only about 100 T. rex fossils have ever been found, and only 32 of those have enough material left to determine they are adults. If there were only 2.5 million T. rex instead of 2.5 billion, Marshall believes we would never even know they existed.
Marshall and his team also thought about modern-day biology when they reached their estimate. Even today, the bigger the animal, the less dense its population. The population density might also have been small because it required more energy to live. A T. rex is also believed to have reached sexual maturity between 14 and 17 years old, and lived to 28 years old.
There is still a huge margin of error for their calculations. Marshall's team was uncertain about how long each generation would live or how large their ranges were. "We estimate that its abundance at any one time was ~20,000 individuals, that it persisted for ~127,000 generations, and that the total number of T. rex that ever lived was ~2.5 billion individuals, with a fossil recovery rate of 1 per ~80 million individuals or 1 per 16,000 individuals where its fossils are most abundant," reads the study's abstract. "The uncertainties in these values span more than two orders of magnitude, largely because of the variance in the density–body mass relationship rather than variance in the paleobiological input variables."
Despite all this uncertainty that comes with trying to understand animals that existed millions of years ago, a study like this is still interesting for researchers. "Previously researchers have tried to estimate things like the likely home range size of Tyrannosaurus, and its basic energetic needs, so this is a neat extension of previous work, and it includes lots of updated information on Tyrannosaurus," Nizar Ibrahim, a paleontologist at the University of Portsmouth (UK) and National Geographic Explorer, who did not participate in the study, told CNN. "We just have to keep in mind that all of these intriguing studies come with a certain dose of uncertainty -- there is just so much we still don't know about dinosaurs, even a Hollywood star like T. rex."
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