Life (Part 2 - origins)

We talked about the mechanics of evolution yesterday, but I still didn't explain how life started in the first place. We're definitely entering theoretical territory today, because nobody knows for sure how the world went from lifeless to the first single-celled organisms.

You can click through this slide show for some of the predominant theories, but the main one is covered better here - basically, amino acids came first. You wouldn't call them life yet, but amino acids are the building blocks of proteins - when amino acids assembled themselves into proteins, the proteins started enacting relatively random processes. Chemical reactions don't require "life" as we would see it - but if a chemical reaction results in replication, now you're starting to look more like a living thing.

Random at first, but once they start connecting to each other the behavior changes

As I mentioned yesterday, this all would have happened over a VERY long period of time. Once cell start copying themselves, sometimes making mistakes that sometimes result in adaptations,  then the evolutionary process has begun, and different species can begin to exist - all single-celled at first, but then another mutation causes cells to start working together and that cooperation has an advantage, so if that 'team' of cells replicates, now there's a multi-celled organism.

The first divisions would have been random, but the resulting cells have a higher chance of dividing again

Another theory is that metabolism came first - metabolism is a lot like a chemical reaction, where a substance is converted into energy. When people say that I have a fast metabolism, they mean that I convert food quickly into energy, so very little of it is stored as fat. Metabolism at these early stages could have begun near deep sea vents, from the heat energy and varied chemicals.

Lava coming out of the ground at the bottom of the Atlantic ocean, creating new land at the fantastic rate of 13 cm per year - and maybe creating some life, too

Both of these have been deemed 'plausible' by lab experiments, but nobody really knows for sure. They also could have happened on another planet and been brought here by asteroids!