How Did Complex Life Evolve In The Deep Sea?

Life was restricted to tiny, single-celled organisms in the ocean's depths for billions of years. Before some of us made our way to land, sophisticated life had been present in the deepest depths of the ocean for almost 15 million years before something caused it to suddenly erupt in population around 570 million years ago. From plants to horses to all marine animals, all multicellular life today can be traced back to that time.

The emergence of complex life from simple organisms is still one of evolution's greatest riddles, if not its greatest mystery. On a fundamental level, all complex forms of life vary from single-celled organisms, and it is unclear how or even when humanity achieved the transition.

According to one idea, the missing piece is Archaea, an early single-celled living form that diverged from other single-celled organisms. Given that life had persisted in its basic form for billions of years without any obvious justification for evolution, it ties into the more general puzzle of why complex creatures even evolved at all.