3 Reasons Dinosaurs Never Really Ruled the Earth

Giant lizards may terrify you in the movies, but are we exaggerating their presence in Earth's history?

When it comes to dinosaurs, we immediately think of giant, bloodthirsty reptiles and their dominance for more than 150 million years.

It's a dramatic retelling of history, but fundamentally wrong on several counts. Dinosaurs may not have been as scary as the filmmakers painted them to be.

Dinosaurs started out as small reptiles.

Dinosaurs are believed to have been the most dominant group of vertebrates throughout the Jurassic period and into the late Cretaceous. But did they really dominate the Earth as history has it? (Photo: Getty).

The oldest dinosaurs we know of date back to about 235 million years ago, during the mid-Triassic period.

Recent finds from Africa, South America and Europe tell us that they were not much larger than a dog, and were tall, thin creatures that ate mainly leaves and beetles.

In contrast, the ancient relatives of crocodiles were much more abundant and diverse. Among the relatives of crocodiles in the Triassic period , there were carnivores with sharp teeth that specialized in chasing large prey on two legs.

They were covered with bony scales and spines, had ostrich-like beaks, and specialized in fern feeding.

Even as the first dinosaurs began to evolve into the main lineage that would thrive for the rest of the Mesozoic, most of them were small and outnumbered by their crocodile cousins.

Then everything changed at the end of the Triassic period, when massive volcanic eruptions changed the global climate , causing many other reptiles to die out, and dinosaurs gradually became dominant.

If this mass extinction had not occurred, we might have had an "age of crocodiles" instead of an age of dinosaurs as recorded in history.

Dinosaurs never evolved to live in the sea.

The largest predators in the Cretaceous oceans were reptiles and sharks, not dinosaurs. (Photo: De Agostini/Getty Images).

Three-quarters of our planet's surface area is ocean, and we cannot say that dinosaurs ruled the Earth if their presence in the ocean was only in extremely small numbers.

Although some dinosaurs evolved to swim, and left traces in ancient shallow waters, there is no record of any species evolving to spend their entire lives in the ocean.

Even penguins - the so-called living dinosaurs - have not evolved the ability to stay at sea like many marine mammals, and must return to land to nest.

Meanwhile, many non-dinosaur marine reptiles of all shapes and sizes dominated the underwater kingdom .

It was this small, abundant life form that allowed marine reptiles to thrive for millions of years, despite climate change and mass extinction events on land.

Mammals thrived during the Age of Dinosaurs

Mammals have coexisted with dinosaurs at every stage of history, suggesting that dinosaurs may not have dominated the Earth as we know them. (Photo: Getty)

Over the past two decades, paleontologists have rewritten the ancient story to show that mammals and their human relatives actually thrived alongside dinosaurs.

Ancient generations of squirrels, raccoons, otters, beavers, aardvarks. and many others evolved through the Jurassic and Cretaceous periods, including primates that lived right under the nose of the tyrannosaurus rex.

Although it is true that all known Mesozoic mammals were small, this does not necessarily mean that they were inferior to dinosaurs.

In fact, researchers have come to realize that the way our ancient ancestors interacted with each other played a much more important role in shaping evolution than dinosaurs.

In fact, even after the dinosaurs disappeared, most mammals that survived the mass extinction continued to evolve to small sizes, suggesting that this was a survival advantage that many mammals had that dinosaurs simply ignored.

And if they hadn't had this evolutionary flair, the dinosaurs' dominance during their time would still be a big question mark.