Not to be jerk, but how can we know with certainty things happened that way, though (is there something I missed)?
You kinda make it sound like all we need is that process, and life should just be. If that is the case, I think we should have been contacted by now, afterall, the Universe is over 13 Billion years old, our planet is about 4 or more, and I am sure there are planets older than ours.
If the process is there, and all the right ingredients, then the chance for life to form is there. That doesn't mean it will necessarily form, but only that all the ingredients are there for it to form. In the case of crystals in a bucket, the way they form is completely unique each time you perform the experiment, but each time the crystals themselves share a similar pattern and eventually things start to happen if you wait long enough. Let's say the chance of life forming was only one in ten thousand, given the perfect planetary conditions, and that the chance of a planet having the right conditions is one in ten thousand; you have a one in a hundred million chance for something to happen.
When you consider that there are over a hundred billion planets in our galaxy alone, and hundreds of billions of galaxies, then that means that there would still be an incredibly large amount of life out there.
I think going off the sheer size, it is kinda silly to think we're alone, but I just wish I could say for sure. Then, it begs the question which is the basis of the Firmas Paradox "why haven't we been contacted"?
My response to that has several parts:
A) If other intelligent life moves to a hive mind system for optical use of resources, then we wouldn't be worth contacting until we develop a hive mind system ourselves. Our planet has yet to awaken in terms of a meta-being. We have the internet, wireless communications, vast cities and technology, so the pulse of a mass sentience may be starting to form, but we're a ways off yet. In the instance of the cell analogy, a single being on earth trying to contact another planet that has a hive mind existence, is like a cell trying to talk to a human. You don't even perceive it. If other planets out there are "awake" as meta-life forms, then humans are only the equivalent of cells on earth in the analogy above.
Other planets might not want to communicate with ours until after we achieve a technological singularity and our planet itself begins to have a life pulse of it's own; a planetary-level consciousness.
B) For other planets that haven't reached a planetary level consciousness yet, they may still view Earth as a "zoo". Think of how bad news travels fast on the internet; as soon as Obama takes a dump you have right wingers on this forum blasting him for wiping his ass the wrong way. In the same fashion, given the type of people on this planet, advanced civilizations may be watching us with a warning sign around us saying "do not enter" or "look but don't touch".
Given that there are problems with parts of General Relativity, such as how things are processed inside of a black hole (the idea of a singularity doesn't "jive" with quantum physics, and Stephen Hawking noted that black holes will eventually evaporate over the course of billions of years, the more likely idea being that quanta will stack into the core of a black hole instead of being a singularity), then it's entirely possible that there are forms of communication that are faster than light.
We see the effects of dark matter but can't perceive it, for instance, so what if it's possible for non-baryon based matter or energy to be lighter than a photon and thus travel faster than light? There are other possibilities, such as warping space itself to travel faster than light. In any case, it's entirely possible that there are billions of life forms with a giant universe-level internet-equivalent that we're just not able to tap into because we can't even begin to perceive it yet.
It's as if you had someone in the 18th century trying to tap into microwave communication - they don't know it's there because it's invisible to them. If you can warp space to travel faster than light, then that implies that it may even be possible to communicate outside of the dimensional brane in which we reside, even that there may be entirely separate universes out there besides our own.
The primitive species won't have the ability to shine dark energy across the universe at us, or may go through a period of trying to communicate using primitive radio waves which require exponentially more power the further it needs to travel for the brief period that they are at our stage of evolution, and the chance of that reaching us are slim to none. When you look at the universe in terms of time, it's key to remember that things have been happening for billions of years and will continue to happen for billions of years. Humans have only been civilized for about 12,000 years, give or take a few thousand years, and we only invented more advanced means of communication in the last 100 years. In terms of time of various planets, suns, star systems, etc., 100 years is almost nothing.
We might be sending out a signal now that isn't responded to for ten thousand years, for example, given how slow radio waves propagate. So I think it's premature to say that there is nothing else out there when we've barely given it any time in the grand scheme of things.
In terms of other answers to Fermi's paradox, this io9 article has some good answers, include the "zoo" hypothesis:
http://io9.com/11-of-the-weirdest-solutions-to-the-fermi-paradox-456850746
