The odds are astronomical. They're astronomically great.
The current theory on the origin of life is that it was preceded by self-replicating molecules. One definition of life is that it must be capable of reproduction, and these fitted that parameter. The first was RNA, which promptly created copies of itself all around the world, and occasionally the RNA surrounded itself with other molecules that protected it, and which could also replicate along with the RNA. These became proto-viri.
The viri further developed survival measures by random bonding and replication errors over hundreds of millions of years. That means sextillions of generations of proto-viri, all over the world, each of which might have had some minute error that might prove beneficial and cause it to reproduce more effectively than other proto-viri. These developed sturdier protein jackets, and even a metabolic system, which oxidized sugars, turning them into energy for use by the now proto-cell.
Energy for use opened up many possibilities, including flagella, propelling the proto-cells to new locations quickly, at several body-lengths per second. No longer did these basic almost-life forms have to rely on ocean currents for movement. Organelles, smaller at first, but then becoming larger in size through the generations through what was now mutation, served vital roles in these early cells. Plasmids detailing the genetic instructions for parts of the cells were exchanged, and new mutations were quickly spread throughout the population. I think a biology teacher told you the rest. And yes, the odds of, in warm, acidic water, full of organic molecules, ribonucleic acid forming is quite likely.
The food chain only occurred because predators reproduced and adapted in a way that they created new niches. Prey developed first, only checked by resources and disease, but then predators, small at first, evolved to hunt different sorts of prey; unlocking a new, bigger food source was a hugely beneficial trait that was quickly passed on. However, hunting the new prey might take the adapted strain of the existing predator elsewhere, and separate the groups. Such separation leads to species differenciation.
This, by the way, is a great opportunity to explain why monkeys don't spontaneously turn into people. Homonids filled a niche that required intellect and the ability to make tools, along with other tasks which need higher thinking. They filled this niche very well. If modern-day chimpanzees were to attempt to outcompete humans in our niche, they would have to spontaneously "turn into humans," something that is biologically impossible, or about as likely as Game Crazy Kid listening to reason, logic, and science.
The niche change was, instead, something gradual and over millions of years. We outcompete monkeys in our niche so hopelessly that they couldn't hope to adapt so as to barge in on what humans do so well. In was only evolutionarily recently (about 300 years or so) that conservational efforts were enacted so as to prevent humans from killing anything attempting to steal livestock or kill in the same area we attempted to. We shoot wolves, trap tigers, fight bears in gladiator arenas because we can, and subject any predator worth its salt to a hunt so fierce it has nearly wiped out a great number of the species.
Nothing can happen evolutionarily, on a large scale, within the time frame of 300 years. It would be like me asking you to put together as much of a puzzle that could be assembled correctly in 1000 different ways out of billions of possibilities as you could in five seconds. Five hours is different. Five years is different.
I might add, at this point, that I find it equally, if not more so, as ridiculous as you find my views that you believe, and hold dear the belief with all your little heart, that God slapped us all (us all being all life) down onto the face of a barren rock in six days, despite the fact that two of those days were measured against a rotation of a planet that didn't even exist yet.
We're the only species that's intelligent enough to hold a conversation (oh, and parrots), but other species have other methods of communication, such as clicks, screeches, thumps, and odors. These, given time, and given a lack of an omnipotent predator having gained control of the planet (that's us), might evolve into complete language.
Finally, I ask you this, in response to your last question:
Do you think purring, fighting, whining, building, climbing, digging, emitting a sound of greater than 200 decibels, running 75 miles per hour, coaxing termites out of a hole with a stick, and singing are nothing more than basic life processes? I certainly hope not.
