On our planet, human beings are the apex creatures. We dominate Earth due to our intelligence and ability to adapt. We are the supreme species, but we weren’t always. Going back millions of years, back before the rise of humans, before even the dinosaurs, there was no life on land, but the oceans were a different story.

Before life on land developed, the ocean was teeming with life, but it didn’t start out with fish. Instead, single celled organisms, like bacteria, were everywhere. While not as interesting or complex as the creatures on earth would later be, they were the first creature inhabiting this planet.

At some point, due to causes scientists don’t entirely know, life evolved. Multicellular organisms began to rise, such as the Trilobite, an arthropod resembling a horseshoe crab, and jawless fish, which are considered the first animals with a backbone. These fish would eventually evolve further into pretty much any animal with a backbone.

Up to this point, the lands on earth were nearly barren of life, with some fungus making up its population of living things. This would change when global cooling, warming and reduced oxygen in the ocean would eventually contribute to more complex animals in the oceans, forced to adapt to survive. Eventually, certain fish evolved to move on land due to environmental pressures and years of evolution. 

While the fish that adapted to land wouldn’t evolve into things like dinosaurs for many, many years, it was the beginning of life as we know it.