One may be drawn to ask the question: why would microorganisms choose to develop the ability to survive and to thrive in such inhospitable environments when there are plenty of other places to live on Earth? But that question assumes that extremophiles came into being after the conception of more regular organisms. Since it is known that the environment of Earth was, at one time, much hotter than it is today; and since many archaebacteria, the root of several models of the tree of life, are thermophilic, some researchers believe that adaptation to extreme conditions is not a feature acquired during the course of evolution, but one that most of todays organisms have lost in the course of an evolution away from hyperthermophilic ancestors (Michael Gross, Life on the Edge). Perhaps, this reasoning suggests, thermophiles came first. Maybe the rest of us are the ones who have made adaptations to new and extreme environments, maybe were the crazy ones. In our search for extraterrestrial life we must realize the flukishness of human existence: we are much more likely to find psychrophiles on planets similar to Mars and thermophiles on moons and planets resembling Europa rather than egg-headed crazies wielding anal probes.