Our planet is about 4.5 billion years old, and life is thought to have first appeared about 3 billion years ago in a marine environment, and even more, it is thought to have appeared by accident, as an extraordinary set of circumstances would have been necessary to give the spark of life.
Early lifeforms would have been similar to the bacterias the we can find today at great depths into the ocean, near volcanic regions. When our planet was about 1 billion years old, oxygen would have been scarce in the atmosphere, so conditions for terrestrial life were virtually none, but for marine life, that’s another story. Underwater volcanoes would have provided heat and minerals necessary for feeding primitive organisms, and these organisms would produce tiny amounts of oxygen in their feeding process, thus laying the foundations of an oxygen-rich atmosphere and terrestrial life.
Just as it happens in today’s world, after the very first microorganisms appeared, evolution kicked in and more and more complex life forms appeared. But however complex, they were still primitive, the oceans were populated by strange jellyfish beings that fed on sunlight, and giant slugs that were probably carnivorous. The being that became the root of all vertebrates has been named pikaia, a polychaete worm that had a proto-notochord, the basis that later evolved in what today is the spinal cord.
Millions of years later, early fish started to appear, they lacked jaws or teeth, and probably fed by sucking in their prey, creating some sort of vacuum with their mouths and respiratory system.
These types of creatures represent the foundation of today’s diverse marine life, but many creatures that live in the oceans made transitions from marine and terrestrial life habits, such is the case of whales, dolphins or seals. This is an interesting fact, that may eventually prove vital for human life. Scientists believe that in order to potentially populate other planets or satellites, humans might need to adapt to marine life, not a very hard thing, if we realize that some geneticists managed to create phosphorescent mice by implanting DNA from marine jellyfish into mice embryos.
Though the length of time until the above mentioned ideas will become “tangible” is going to be measured in centuries, we can all begin to ponder the fact that without marine life, our species would never have existed, and if we’re not careful about how we can protect today’s sea creatures, we might be heading towards extinction.
