When approaching the Fermi paradox astrobiologists usually use the principle of convergent evolution [1], where multiple types of life will evolve similar featu

When approaching the Fermi paradox astrobiologists usually use the principle of convergent evolution [1], where multiple types of life will evolve similar features because of similar environmental pressures. (the application is the development of intelligence.) I'm a big fan of this, because it affirms my hope that life exists elsewhere. But unfortunately we don't really know what "life" and "intelligence" is -- an intelligent dolphin might never think or desire to leave the ocean, and an intelligent four-legged creature might never think to look up at the sky and wonder, the way that humans have always done. http://en.wikipedia.org/wiki/Convergent_evolution http://en.wikipedia.org/wiki/Convergent_evolution