The statistical theories could all be true about how much life “should” be out there. The problem with intelligent life? If we knew where it was, communication could take hundred or thousands of years to establish a single idea or thought simply because of the time it takes light to travel. We haven't existed long enough for that to happen. Hell, we actually were "just born yesterday" in the grand scheme of things. If intelligent life on a planet exists for 1 million years, the possibility that they evolved in a solar system at the same rate we did (within a few thousand or hundred thousand years) would be very rare. Billions of years are a lot of years. We may indeed one day realize that the universe has “teemed” with life at varying levels in varying locations. But, as the article points out, relating to all of time (tens of bilions of earth years), planetary systems are rarely stable enough to go relatively undisturbed for a length of time suitable for intelligent life to evolve.
Anyway you slice it, either we are very lucky or our existence is planned, engineered and created. ;o) I don't believe in luck.
Even if there was a predictable, smooth path to intelligent life, given the right conditions (where the conditions were fairly rare), let’s do this thought experiment:
Let’s say there are 100 civilizations RIGHT NOW in the Milky Way that our at our CURRENT level of technology. Let’s further say that they are more or less evenly distributed throughout the Galaxy.
We have been transmitting modulated radio signals for about 100 years (give or take, I won’t quibble, just using a round figure).
That means that there is a 100 light year radius “bubble” around our solar system where Earth’s transmissions can be detected.
Similarly, the other 99 civilizations too have roughly 100 light year radius bubbles around them.
Evenly distributed, these bubbles would be THOUSANDS of light years apart, keeping all 100 civilizations from knowing about each other’s existence for long, long stretches of time, probably longer than the civilizations could survive.