Scientists Estimate 1.7 Billion T. Rex Roamed Earth — Here’s How They Figured It Out

T. rex, or Tyrannosaurus rex, is often dubbed the king of the Mesozoic Era when the dinosaurs roamed and ruled the Earth, about 252 to 66 million years ago. It is one of the most dominant species during its time, so much so that its name was just a translation of “tyrant lizard king”.

Which is why when people hear that scientists have estimated the total number of these giant reptiles to be in the billions, most could not believe it. However, they used real math and science to work out an estimation, which turns out to be a lower figure than previously calculated.

How Do Scientists Estimate Dinosaur Numbers?

The people who studied dinosaurs and their remains, paleontologists, estimate that the total number of T.rex that existed on Earth was about 1.7 billion. But how could they know this number? They can’t just dig up the dinosaur’s fossils, count them, and call that the total number.

The formula for estimating this amount is directly related to how long a specific species can live, how many offspring it produces, and what is the population of the species at one place at any given time.

In the T.rex case, scientists estimated that they can live up to 28 to 30 years, have 20 or more eggs, and have about 20,000 individuals at any time of their existence. Then they multiplied this number, along with a few other factors, to come up with the estimate.

Read more: Paleontology

What Was the First Big Estimate—2.5 Billion?

T-Rex Facts for Kids | All about the Tyrannosaurus Rex

In 2021, a study was published in Science that suggests the estimate to be about 2.5 billion T. rex. Their findings were that there were around 20,000 T. rex alive at any time, and that the species lasted for about 127,000 generations. By multiplying those amounts, they were able to come up with the bigger number.

Based on that number, only about 1 in 80 million T.rex became a fossil that we can find today. This number reflects and supports just how rare it is to find a dinosaur’s remains.

A New, Lower Estimate—1.7 Billion

A newer study has recently suggested another alternative estimation for the total number of T.rex that existed on Earth. The scientists found that T. rex lived for around 96,800 generations and probably only had about 19,000 individuals at any point in time.

Both of these estimates are lower than the first study, resulting in a product of 1.7 billion, which is 800 million less than the earlier estimate. The scientific community finds it realistic and is more inclined to this newer number because it was estimated using better technology, data, and understanding.

Read more: Science Alert

Why Do Estimates Change?

T.rex Ambush | Walking with Dinosaurs | BBC Earth

Some people think that once Science presents a fact based on evidence that it will forever remain the truth. However, these facts are not always absolute and can be revised or completely debunked based on the existence of newer evidence or better data.

The 1.7 billion estimate fixes some mistakes of the older model, such as overlooking or overestimating how long T. rex lived, how quickly it reproduced, and how strong its babies were before they grew up. Additionally, the recent estimate aligns better with animals we see today, like birds and reptiles that lay eggs.

However, the older model, which states a total of 2.5 billion T.rex have ever lived, is not completely wrong, even if the number has changed. It just meant that as science improves, and more evidence arises, we get closer to the truth.

Author's Final Thoughts

Scientists did not just count the number of T.rex bones and remains they have found on the ground to come up with an estimated number. They use math, science, and information from different animal species alive today, such as birds and reptiles, to create a hypothesis on how many T. rex lived.

The first big guess was 2.5 billion, but new research suggests it is closer to 1.7 billion. Regardless, both numbers were very large and dramatically reflect just how much the “tyrant lizard king” dominated its era.

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