For a few decades, those believing

For a few decades, those believing that the chances for life elsewhere in the Universe are small have made circulate a theory that backs up their claims, known as the anthropic argument. Essentially, it states that the period of time it takes life to evolve is longer than the period in a star's life when it can sustain it on planets around it, and that, therefore, complex life must be very rare. Now, a new study comes to question this established line of reasoning, and proposes that complex life may occur more often and under less conditions than first thought, Space informs.Astrophysicist Brandon Carter was the first to propose the anthropic argument back in 1983, after successfully conducting remarkable work in the field of anthropic principles back in the 1970s. The driving force behind his argument is the assumption that the life cycle of a star is completely independent from the time frame complex life needs to appear and develop. In a new scientific study, astrobiologist Milan M. Cirkovic and colleagues argue that this argument is obsolete, because it has been proven that no body in, for example, the solar system, is completely independent from others. “There are many different ways in which planets in our solar system are not isolated. We must not regard habitable planets as closed boxes. If you abandon that assumption of independence, then you have a whole new background in which you can set up various models of astrobiological development,” explains Cirkovic. He adds that influences that could lead to the emergence of life on a certain celestial body could come from a variety of sources, such as gamma ray bursts, nearby supernovae, and perturbations of comet clouds.“A gamma ray burst won't affect whether life will begin at some particular point in time, but it would affect how quickly life develops or takes hold by causing changes in atmospheric chemistry on the planet. This can be interpreted as resetting astrobiological clocks which tick on each habitable planet in the Milky Way,” the expert adds. It may be, Cirkovic adds, that gamma-rays act like an astrobiological reset button, wiping out early attempts at life, and giving stars and their planets a new chance to sync up and attempt to produce life. “The speed of evolution is very variable. There is no reason to think that life on Earth has only one single origin. It is quite possible that there were several beginnings of life on Earth,” he concludes. The study detailing his idea appears in the June 2009 issue of the journal Astrobiology.