The Earth has directly witnessed the coming and going of different species along the timeline due to different mass extinctions or explosions of biodiversity. Therefore, studying fossils helps us to pursue this puzzle and estimate the population size of species from their first emergence to their extinction, in one way or another.
Now, a team of scientists from has wanted to extract this data from one of the most famous dinosaurs in history : the Tyrannosaurus rex. According to his calculations, the number of T. rex that roamed the world is staggering: about 2.5 billion individuals.
How did they calculate this figure?
To establish a reliable estimate of the total population of a dead species, experts follow a method similar to that used for living species, with a methodology with its own name: Damuth’s law.
This law, an ecological equation that states that average population density can be predicted based on body size, where larger animals will have smaller populations compared to smaller creatures (imagine elephants versus ants).
What can this information be used for?
In addition to getting an idea of the population of the animal, it can also provide us with an idea of past ecologies and species that are missing from the fossil record , as an estimate of the total population of the iconic predator can teach us things about dinosaurs that they fossils cannot.
“Establishing the physiology of T. rex has proven challenging,” the authors wrote in their article published in the journal Science . And it is that a species with a slower metabolism could sustain a higher population density greater. And whether dinosaurs were hot or cold blooded is still a hotly debated topic in the scientific community.
How to weigh this debate?
The researchers decided to assume an intermediate physiology , halfway between a large carnivorous mammal and a large land lizard like a Komodo dragon.
Because so much is still unknown about dinosaurs, and given the incomplete nature of the fossil record, the notion of being able to reliably estimate the number of populations of long-extinct species has been dismissed as an impossibility, but scientists weren’t looking for find a single definitive answer, but set limits on what they thought might have been a plausible number. Despite the uncertainties, the model presents a robust qualitative result, according to experts, for one of the largest carnivorous theropods known to science.
As the approach used has great potential, the scientists hope to expand this work to all dinosaurs that exist within the T. rex ecosystem. Many think that his work could be used to estimate the total number of any extinct species, provided we have the necessary information to do so (knowing the body mass, whether it ate meat or plants, or whether it was a warm or cold-blooded animal).
Referencia: C.R. Marshall el al., “Absolute abundance and preservation rate of Tyrannosaurus rex,” Science (2021). science.sciencemag.org/cgi/doi … 1126/science.abc8300
