I recently read an article that discussed the impending search for the spectral signatures of organic life. That search is going on now and is expected to yield positive evidence soon enough. All such estimates are based on the probabilities revealed by a revised formula.
However, the search for "intelligent life" (don't be so homo-centric by calling it "human") may take much longer since it assumes that "they" will be transmitting electromagnetic signals. http://io9.com/what-a-brand-new-equation-reveals-about-our-odds-of-fin-531575395 http://io9.com/what-a-brand-new-equation-reveals-about-our-odds-of-fin-531575395
