Transcript: The very limited evidence that we have is consistent with the supposition that microbial life is quite common in the universe whereas intelligent life is quite rare. Evidence in favor of microbial life being potentially common is the fact that carbon, nitrogen, and oxygen, the essential life elements, are created readily in stars throughout the Milky Way and beyond, the fact that planets are found to exist around solar stars, even if Earth-like planets have not yet been found, the fact that life on Earth formed early in the history of this planet, that it is robust, and that microbial life has diversified into many evolutionary niches. Arguing against intelligent life being common is the fact that it happened relatively late in the evolution of life on Earth, after four billion years of evolution, the fact that only a handful of species under the most generous definition have evolved intelligence out of hundreds of millions in the history of Earth, and the fact that intelligent life forms like us are fragile, and that the idea of intelligence and communication may be a cultural tendency rather than a biological directive.