Intelligence can be difficult to quantify, as we use ourselves as a basis for comparison. Dolphins and whales may have a higher intelligence than humans due to their large brains and problem solving capability, but they are adapted to a marine enviroment. They can succeed very well in that environment, but have no need to develop a civilization, although they do have families and groups.
It has been demonstrated that some orangutangs and sea lions can out score some human in certain memory and association tasks.
The early earth atmosphere was mostly methane, and early micribial life ate the methane and produced oxygen as a by product. Even today there are microbes living on black smokers at the bottom of the ocean in temperatures that would instantly destroy life we are more familiar with.
Given the huge variety of forms life can take if given the right conditions, it would seem feasable that not only would life not be such a rarity in the universe, but due to the extreme numbers of stars and planets, the odds are that there are other societies that have developed technologies. The odds are greater based on what we see on earth, that intelligence can take many forms, and tends to adapt to a particular environment.
One thing that came to view on another thread, is that outside of the few signals we ourselves have sent into space, the earth is mostly invisible to others in the bandwidth we are searching for ET in. If ET is observing frequencies other than what we are using due to the quietness of the bandwidth, then we may be detectable within 75 or so light years, whenever we started radio broadcasts. Much farther than that and earth is mostly invisible, so one could ask why would ET broadcast their existance when we on earth do not.
The chance of a technologically developed civilization is certainly there, and worth searching for. It's a bit like playing the lottery. The chance of winning is small, but the payout can be huge.
Warning, addicted to SETI crunching!
Crunching as a member of GPU Users Group.