The Sustainability Solution to the Fermi Paradox

Background: The Fermi Paradox According to a simple but powerful inference introduced by physicist Enrico Fermi in 1950, we should expect to observe numerous extraterrestrial civilizations throughout our galaxy. Given the old age of our galaxy, Fermi postulated that if the evolution of life and subsequent development of intelligence is common, then extraterrestrial intelligence (ETI) could have colonized the Milky Way several times over by now. Thus, the paradox is: if ETI should be so widespread, where are they? Many solutions have been proposed to account for our absence of ETI observation. Perhaps the occurrence of life or intelligence is rare in the galaxy. Perhaps ETI inevitably destroy themselves soon after developing advanced technology. Perhaps ETI are keeping Earth as a zoo!