You Can't IMAGINE What Existed Before Dinosaurs

53 crore 88 lakh years ago, Earth was in the midst of the Paleozoic Era—a time that spanned until about 25 crore 20 lakh years ago. This era, predating the dinosaurs, is a subject of great mystery and intrigue for us. It belongs to a prehistoric time, where evidence is scarce and the remnants we do have leave us with more questions than answers. Today, if you were to ask anyone which period would be the hardest for humans to survive, most would probably point to the age of dinosaurs. After all, who would want to live among 10 to 100-foot-long terrifying creatures? But you say this because you have no idea how dangerous and unforgiving the world was before the dinosaurs even existed.

The world before the dinosaurs is still shrouded in mystery, and very little has been revealed about it. However, in today’s article , we’re going to explore that ancient world and uncover the reality behind the evolution of life on Earth.

Hello guys, I’m Kaushik, and let’s dive into another exciting episode [Music].

We all know that Earth was formed about 4.54 billion years ago. But life as we know it began to take shape around 541 million years ago when the Paleozoic Era kicked off. This era, lasting over 200 million years, was a time of significant change—an era marked by the brutal challenges faced by life on Earth. It’s divided into six periods: the Cambrian, Ordovician, Silurian, Devonian, Carboniferous, and Permian. Each of these periods was crucial in shaping the history of life on Earth.

The Cambrian Period, which started around 541 million years ago and ended about 485 million years ago, was when life on Earth began to diversify dramatically. Before this, life was mostly unicellular, small, and simple. But as the Cambrian period began, there was an explosion of multicellular life, especially in the oceans. This "Cambrian Explosion" wasn’t a literal explosion, but rather a metaphorical one, signifying the rapid development of new life forms.

During this period, the first arthropods came into existence, eventually evolving into the insects we see today. Even vertebrates—creatures with backbones—first appeared during this time, laying the groundwork for all future animals, including humans.

But don’t be fooled by the idea that life in the sea was peaceful. If you were to travel back in time, you would likely flee in terror from some of the creatures that thrived back then. Take trilobites, for example—marine insects that could grow anywhere from 6 to 60 cm long, or even larger. But they were nothing compared to predators like Anomalocaris. This fearsome creature ruled the Cambrian seas with an iron grip—or rather, with powerful claws and jaws that made it a terrifying predator. Its mid-gut glands allowed it to digest its prey rapidly, making it one of the most efficient killers of its time.

However, like all empires, the reign of the Cambrian predators eventually came to an end, around 485 million years ago, when the Ordovician period began. This period brought massive changes to the world. Carbon dioxide levels were much higher than they are today, and sea levels were at their peak. Much of what is now North America was submerged under water, and even the highest peaks we know today, like Mount Everest, were once beneath the sea. Evidence of this has been found in the form of Ordovician rocks on Everest, revealing that even the highest points of the Earth were once part of the ocean floor.

With the expansion of the seas during the Ordovician period, new species emerged, such as bryozoans, crinoids, brachiopods, snails, cephalopods, and blastoids. But while life flourished under the waves, a new form of life was beginning to take hold on land. Around 470 to 460 million years ago, the first plants—liverworts and mosses—began to grow on Earth, marking the beginning of terrestrial life.

The spread of these plants, however, had a catastrophic effect on marine life. As plants absorbed carbon dioxide from the atmosphere, global temperatures began to drop. Marine animals, adapted to warm and shallow waters, found their habitats disappearing. This led to one of the most significant mass extinctions in Earth’s history, wiping out around 85% of existing species in what is now known as the Ordovician-Silurian extinction event.

This event marked the end of the Ordovician period but paved the way for the Silurian period, a new chapter in the evolution of life [Music].

So, after the devastation of the Ordovician period, the Silurian period began around 443 million years ago. It was a perfect time for the evolution of both marine and terrestrial life. For the first time, jawed fish appeared, including both cartilaginous and bony fishes. Cartilaginous fish, with their strong jaws, became lethal predators, much like the sharks of today. In contrast, bony fish developed less powerful jaws but are now the most common fish in our oceans, making up about 98% of the species we see today.

On land, the Silurian period also saw the first appearance of more complex life forms. Fungi and bacteria were already present, but multicellular life began to take shape, leading to the first terrestrial creatures like centipedes and arachnids. Arachnids, which include familiar creatures like spiders and scorpions, were among the earliest animals to venture onto land.

In just three periods of the Paleozoic Era, life on Earth transformed from simple unicellular organisms to complex multicellular beings. But this was just the beginning. The remaining three periods of the Paleozoic Era would bring even more incredible changes, with stories and creatures that will both amaze and terrify you.