Originally Posted by Wheeldog

Statistically, so-called intelligent life likely does exist elsewhere in the universe. Amost certainly there are many other planets beyond our solar system that host life. However, if there is senscient life somewhere out there there is a surprising lack of concrete evidence of its existence. All things considered, if there are several planets with intelligent life at least one of them should have progressed to the point of using some form of radio transmissions and possibly established themselves on other planets. Yet all the efforts to detect extrasolar radio transmissions to date have been strikingly unsuccessful. Other than the natural sounds and signals generated by stars and other bodies, space is hauntingly silent.

There is one school of thought that speculates that intellegent life on another planet would likely follow much the same pattern as has happened on earth. It would progress through primative stages learning to tap into stores of natural energy such as coal, oil and natural gas gaining in numbers and power as time passed. However, every planet would have a finite ability to meet the energy and other resource demands of a civilized specie. Even though the intellegent life specie might reach the point where it could begin to colonize other worlds, the host home world would be exhausted before this step could be carried out. In other words, they probably would be faced with the same limits that we are now experiencing.