Cambrian - Age of Light

This week's image comes from a staggeringly long time ago. Dinosaurs have their share of spectacle, but before their trademark gigantism was an entire alien world of animals the likes of which have never been seen since. Here, we stand at the most bizarre point in Earth's history- the climax of the Cambrian explosion 500 million years BCE. Life has been slowly evolving for three billion years now, but it has yet to take root above the surface of the ocean. The land has been roasted in the Sun's destructive radiation, and the atmosphere largely consists of carbon dioxide- much too dangerous for even bacteria to survive up there.
However, it is just this destructive force that sets life on the most important journey yet. As venturing close to the surface imposes certain death, animals that learn how to detect light, be it through feeling it or developing extrasensory pits on their skulls, have a clear advantage. The recent global glaciation period dimmed the lights, but not the UV radiation it carried. That meant these organs had to develop further to save the organisms that held them. Eventually, these organs became so refined that they could make out high-definition images of the world around them. The first eyes had evolved.
When the glaciers receded and the sun came back through, the oxygen byproduct from the nearby plants had already started to bond and form Ozone in the upper atmosphere. Light was now no longer a hazard but a tool. Eyes turned from defense mechanisms to predatory weapons. If you could see something, you could eat it faster than someone who couldn't. With the dawn came the start of a new competition. New features were bred into these animal's genomes such as armor, limbs, mandibles, and claws. Eventually, this gave rise to the most massive predator until that point- the Alien Shrimp Anomalocaris. It may not be so impressive by today's standards- the largest were only three feet long. However, this was easily enough to literally crush the competition.
Even so, there was another anomaly that came from this era- a half-inch-long lamprey-like fish called Pikia. This animal and others like it lacked the hard shells of more dominant animals like the trilobites or Anomalocaris, but it had a wild card that nobody could have accounted for: the first bony backbone. This deceptively irrelevant adaptation laid the foundation for a centralized nervous system, paving the way for not just smarter animals, but eventually bigger and stronger ones as well. Among these include the entire caste of Vertebrates, including all bony fish, amphibians, reptiles, mammals, and- eventually- us.
Five hundred million years is still a long way to go, though...

Rendered in Photoshop 7.0