A single Tyrannosaurus rex is unsettling enough, and scientists estimate that there were once about 2.5 billion Tyrannosaurus rexes on the planet.
Tyrannosaurus rex is the largest land animal known to have ever lived on Earth, with adults averaging about 5.2 tons and some reaching 7 tons. Based on fossils from different time periods found around the world, it is speculated that Tyrannosaurus rex lived in present-day North America at the end of the Cretaceous period (about 68 million years ago to 66 million years ago) and existed for a span of about 1.2 million to 3.6 million years.
A study published April 16 in the journal Science provides the first estimate of the total number of Tyrannosaurus rexes. And in the last century, the famous paleontologist George Gaylord Simpson thought it was impossible to do.
The University of California, Berkeley (University of California, Berkeley) research team, using data on the size of the Tyrannosaurus Rex, the time it took to grow to adulthood, and the energy required for the creature to survive, speculated on this figure.
They estimate that there were an average of 20,000 adults at any one time during the time Tyrannosaurus rex existed, and that they bred for 127,000 generations over a span of two to three million years, resulting in a total of 2.5 billion Tyrannosaurus rexes on Earth.
Two and a half billion sounds like a lot. Considering the total number of births over millions of years, the study analyzed that they were not densely distributed at any one point in time – the equivalent of only two in a place the size of Washington, D.C., or 3,800 in a place the size of California.
The researchers followed some general laws of biology to make their projections. For example, the larger the animal, the smaller the density of distribution. Plus the energy they need to survive to estimate. The study estimated that the energy required for the survival of Tyrannosaurus rex between Komodo lizard (Komodo dragon) and lions. Similarly, the greater the energy required for survival, the smaller the density of distribution of the animal. Furthermore, the study also considered the lifespan of each Tyrannosaurus rex to estimate the number of generations they reproduced. They estimated that the average Tyrannosaurus rex to 14 to 17 years to reach adulthood, life expectancy is about 28 years.
Charles Marshall, a paleontologist at the University of California, Berkeley, who led the study, said the estimate, of course, contains many uncertainties, such as the paleontological data from the excavation of Tyrannosaurus rex, the time span of their existence, the number of generations that reproduced, and so on.
The greatest uncertainty, Marshall said, is probably the ecological characteristics of the dinosaurs. Ecological characteristics refer to an animal’s pattern of interaction with its surroundings, and also include the extent to which T. rex was a warm-blooded animal.
They drew on data from a study at the University of California, Santa Barbara (UC Santa Barbara) to speculate on the ratio between animal weight and distribution density. But even though the relationship is clear, Marshall says the ecological characteristics of different animals still play a big role. For example, jaguars and hyenas are about the same size, but the distribution density of hyenas is 50 times greater than that of jaguars.
Marshall said, “Surprisingly, ecological characteristics are the dominant uncertainty in this estimate rather than the paleontological data we used.” They projected the total number of Tyrannosaurus rex to be somewhere between 140 million and 42 billion. 2.5 billion is the number to take.
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