Billions of T. rexes roamed the Earth over their lifetime, new study says - CNET

At the high end, it's probably less than half the total number of humans that have ever lived.

The result: probably about 2.5 billion altogether, but the number could actually be as high as 42 billion.

That high-end number is probably less than half the total number of humans that have ever lived, but it's still a lot of huge, hungry prehistoric predators, especially when we consider what a relatively rare find T.

Billions of towering carnivores living over a few million years is still a much lower population density than that of humans today, of course.

The study estimates the total population of T.

While the simulation found 2.5 billion total T.

rexes as its best guess, the correct figure could actually be somewhere in a wide range between 140 million to 42 billion.