Some spoilers to follow.
In one sense the numbers are stacked in life's favour with there being billions of potential stars and current data suggesting there are billions of planets that could sustain life. Cox does a good job of explaining why the odds vastly reduce when you consider the possibly unique event of the symbiosis that created eukaryotic life on our planet. He then reduces the odds further by introducing the Fermi paradox which states any intelligent life existing 10 million years prior to us would have fully colonised the galaxy. I guess they could be more adherent to the laws of Star Trek in not interfering or civilizations burn out before they can escape their gravity well.
The show ended well with the sobering thought that if we are the only intelligent beings* out there ** then we have a responsibility to protect this unique situation and to go out there and explore. I particularly like the latter idea (it should also help with preserving other life on earth) of us going out there and colonising (preferably empty planets as opposed to conquering others). I'm a firm believer of humanity having to create its own aliens - give us a few millenia on different planets separated by near impossible distances and we'll eventually evolve into our own Klingons and Ewoks.
Anyway - a solid episode that has me willing to give the remaining episodes a chance.
*Don't worry he acknowledges there's plenty of intelligence on our own planet - something I think we really need to acknowledge. His point was that none of these animals are physically capable of building things (with the exception of primates and possibly the octopus with some minor mutations) that would allow them to communicate beyond the stars.
** He sticks to the Milky way for what I assume is the fact that a) all bets are off when you include the universe (as you multiply the chance by at least 100 billion) and b) the distances between galaxies are vast even if you happened to be next door to an intelligent galaxy.