A group of researchers led by the University of California Museum of Paleontology director, Charles Marshall, asked themselves how many tyrannosaurus rexes wandered the earth.
During their reign of several million years, the team estimated that the total amount of T. rexes that once lived and died is approximately 2,500,000,000. Scientists have never before been able to make a rough estimate of the total population for long-extinct animals akin to the tyrannosaurus rex.
T-Rex. - Image Credit: Orla via iStock/Getty Images - HDR tune by Universal-Sci
According to the paper published in the journal Science, this estimate may still contain a substantial margin of error. It is, for example, still uncertain how long a single generation of tyrannosaurus rexes lived. It is also not precisely known where and on how many locations on the planet they lived. And on top of that, there are still a lot of open questions regarding the precise nature of the T-rex's ecology.
The estimates rely on data distributed by John Damuth of UC Santa Barbara that compares the body mass of living animals to their population density, a connection that is known as Damuth's Law. An important caveat is that, although the relationship is substantial, ecological differences result in significant fluctuations in population densities for animals with the same physiology and ecological niche. For instance, jaguars and hyenas are approximately the same sizes, yet hyenas are found in their natural environment at a density 50x higher than the density of jaguars in their natural habitat.
Marshall was, therefore, swift to mention that the degree of uncertainty in his team's calculations is substantial. Although the population of Tyrannosaurus rexes was most likely about 20,000 adults at any given point in time, the 95% confidence range (the population range in which there is a 95% chance that the actual number lies) is from 1,300 to 328,000 individuals. This means that the total number of individual T-rexes that ever existed most probably ranges between 140 million at the low end and 42 billion at the high end.
Even though there probably were billions of them, relatively few fossils of the tyrannosaurus rex have been found so far. Paleontologists have discovered about 100 specimens, 32 of which were the size of an adult specimen.
Scale chart for some of the larger specimens of Tyrannosaurus rex that have been found - Image Credit: KoprX via Wikimedia commons - size edit by Universal-Sci - (CC BY-SA 4.0)
Marshall believes his calculation framework for estimating extinct populations will stand and be helpful in evaluating populations of other fossilized creatures. According to him, this has been a paleontological exercise in how much we can know and how we go about knowing it.
The framework has been made publicly available by the science team as computer code so that others can have a crack at it. Marshall believes that the code can also be helpful in determining how many species paleontologists may have missed when excavating for fossils.
If you want a more detailed overview of what the study was all about, be sure to check out the paper published in Science listed below.
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