Imagine this. Billions of years ago, before humanity, before the earth itself was anything remotely the way it is now, before even our solar system was the way it is now, the planet Mars was covered in free-flowing water. I'm not making this up--it's currently near-proven, an almost non-theory. From studying the rocks and rock formations on the surface, it sure looks like there were oceans of water at some point.
Now imagine that in that mineral-rich Martian ocean live tiny organisms, extremely small, uni- or multicellular, that have for thousands of years, for hundreds of thousands of years, (or for millions more) lived happily, not worrying about a thing.
The organisms that live at the bottom of our own oceans--miles down where no sunlight reaches, and thus no photosynthesis can occur--survive solely on the chemicals released into the water by underground vents. These vents are pumping water at nearly 750 degrees Fahrenheit into water that is just above freezing. Thus the animals living there must be able to withstand shifting temperatures of hundreds of degrees, changing like a whim.
So imagine billions of years ago, Earth is still a craggy, unfortunate rock. Mars, however, is a sea-rich world, which (also unfortunately) is about to be hit by an enormous asteroid the size of Texas. Or the size of Europe.
The impact of that asteroid throws enormous pieces of rock into the atmosphere, and inside those chunks of rock could be pockets of this Martian ocean. And in those pockets of Martian ocean, traveling through the climatic shifts of interplanetary travel, live some of these tiny creatures who like being hot and then cold and then hot and then cold again.
Some of those pieces of rock land on the surface of the earth. And then those organisms fall down into our own fledgling oceans. And the rocks crack open.
In this way, evolution doesn't begin as we think it might. Evolution begins billions of years earlier, on an entirely different planet.