The early history of Earth covers such vast stretches of time that years, centuries and even millennia become virtually meaningless. The first four billion years of its development are known as the Precambrian period. For the first billion years or so, there was no life in Earth. Then the first single-celled life-forms, early bacteria and algae, began to emerge. We don’t know where they came from or even if they originated on this planet at all. This gradual development continued until around four billion years ago when suddenly (in relative geological terms) more complex forms of life began to emerge.

Scientists call this time of an explosion of new forms of life the Paleozoic Era and it stretched from around 541 to 250 million years ago. First of all, in the oceans and then on land, new creatures and plants began to appear in bewildering variety. By the end of this period, life on Earth had exploded into a myriad of complex forms that filled virtually every habitat and niche available in the seas and on the planet’s only continent, Pangea.

Then a mysterious event that became known to early paleontologists as “The Great Dying” wiped out more than 95% of all life on Earth. No one is entirely certain what caused this, but the effect of this cataclysm was as if someone had pressed a great, cosmic “reset” button and it took 30 million years for the development of life on Earth to start again.
The next period of Earth’s history is known as the Mesozoic Era, from about 252 to 66 million years ago. This era is further divided into three periods, the Triassic, Jurassic and Cretaceous. During this era, one type of life came to dominate the planet more completely and for a longer period than had been seen before or since; this was the Age of Reptiles.
Beginning in the Triassic but especially in the Jurassic period, reptiles came to dominate the oceans, the land and even the skies. There has never been anything else quite like this period in terms of the success of a particular type of creature. For almost 200 million years, reptiles were the only significant creatures on Earth. They were so successful and so diverse that they evolved to take advantage of every available habitat and no other type of large creature had a chance to develop.

The massively popular 1990 novel Jurassic Park by Michael Crichton and its subsequent movie adaptations led to a huge resurgence in interest in dinosaurs and the prehistoric world. That interest continues to the present day, even though most of the dinosaurs in Jurassic Park weren’t actually from the Jurassic period. Triceratops, Velociraptor, Tyrannosaurus Rex and the huge sauropods such as Brachiosaurus that feature in the book and movies all actually belong to the Late Cretaceous period, more than 40 million years after the end of the Jurassic. Regardless, the movie made certain kinds of dinosaurs instantly recognizable, even if associated with the wrong era.

Thanks to the movie, there has been some unwitting confusion over the identity of the Velociraptor, and this confusion was due in large part to the fact the name sounds far more scary than the creature to which the name originally belonged. Moreover, the creature to which the label was applied in the novel and movie was actually a distant cousin named Deinonychus, but as the story goes, the author, Michael Crichton, thought “Velociraptor” sounded “more dramatic.” The actual Velociraptor lived not in the badlands of North America, but in the badlands of central-eastern Asia, and it was not nearly as intimidating as Deinonychus.