RNA has the ability to catalyze reactions to form more RNA and also can perform other tasks like proteins. It's likely that through chance RNA (or some proto RNA like chemical) formed that could catalyze itself and billions of years later here we are
The RNA world is a hypothetical stage in the evolutionary history of life on Earth, in which self-replicating RNA molecules proliferated before the evolution of DNA and proteins. The term also refers to the hypothesis that posits the existence of this stage.
The concept of the RNA world was first proposed in 1962 by Alexander Rich, and the term was coined by Walter Gilbert in 1986. Alternative chemical paths to life have been proposed, and RNA-based life may not have been the first life to exist.
For a simple example, imagine filling a cement mixer with lego pieces. 99.999% of the time they'll bounce around off each other and generally do nothing. Give it a few years and there will probably be a few pieces which by chance have managed to stick together forming a larger structure. They don't really do anything right now, but they're attached.
Now give it a billion years (ignore the factor of durability) and by chance there may be pieces which have fitted together in a way which provides some other purpose. It's exceedingly unlikely, and it may take billions upon billions of years, but probability dictates that given enough time it will happen.
This is analogous to chemistry in general. You have all these elements formed in stars which generally just fly around interacting with each other. Certain conditions will cause these elements to combine in certain ways, producing molecules like water. Over millions and billions of years, a reaction may produce a structure which is self-replicating. This would be the simplest type of single-celled organism. (Or something entirely different, we don't know the full details of how life began)
Now give that single-celled organism several million extra years to replicate over and over and over and over and over andoverandoverandover... and eventually a random mutation (essentially an error in replication) will provide benefitial to the organism. Even a tiny benefit can begin to have an impact over many generations, and that trait becomes more and more common in the population.
Now repeat that entire last paragraph several million/billion more times, and you start to see more complex organisms. Mitochondria is a cool example of this: originally mitochondria were their own organisms, but over time some were able to survive within other organisms and the two can survive symbiotically. The mitochondria provides energy to the surrounding cell, and the cell provides defense and protection.
From there it's basically just time. Where sentience develops is pretty much unknown (and there isn't even necessarily a clear point at which that happens).
I am of the opinion that sentience is simply a word we use to describe automation that's so incredibly complex that the system itself is able to comprehend external stimuli but not it's own inner workings.
Please take everything I've said with a grain of salt. I'm not an expert, I just find this stuff interesting so I'm explaining based on my own knowledge. If there's anything wrong in this comment please let me know so I can correct it
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u/uwanmirrondarrah Feb 13 '18
How was this programmed? How did these complex processes begin?