"The evolution of complex life on other worlds is rare in frequency but large in absolute number," according to new research from a team led by Louis Irwin—from the Department of Biological Sciences, University of Texas at El Paso. Their findings are based on the first plausible "assessment of complex life in the Universe using empirical data."
The BCI ranks planets and moons by basic, first-order characteristics detectable with available technology. By our calculation only 11 (~1.7%) of the extrasolar planets known to date have a BCI above that of Europa; but by extrapolation, the total of such planets could exceed 100 million in our galaxy alone. This is the first quantitative assessment of the plausibility of complex life throughout the universe based on empirical data. It supports the view that the evolution of complex life on other worlds is rare in frequency but large in absolute number.
Rational speculation about biological evolution on other worlds is one of the outstanding challenges in astrobiology. With the growing confirmation that multiplanetary systems abound in the universe, the prospect that life occurs redundantly throughout the cosmos is gaining widespread support. Given the enormous number of possible abodes for life likely to be discovered on an ongoing basis, the prospect that life could have evolved into complex, macro-organismic communities merits serious consideration.
The team says that only 11 of the more than 1,700 planets so far discovered in the Milky Way have a higher BCI than Jupiter's moon Europa.
The paper was published in Challenges of Astrobiology by Louis Irwin—from the Department of Biological Sciences, University of Texas at El Paso—Abel Méndez—from the Planetary Habitability Laboratory, University of Puerto Rico at Arecibo—Alberto G. Fairén—from the Department of Astronomy, Cornell University—and Dirk Schulze-Makuch—from the Center of Astronomy and Astrophysics, at Technical University Berlin.
The Daily Galaxy via http://www.mdpi.com/2078-1547/5/1/159
Image credit: http://blog.journals.cambridge.org/2013/06/how-the-drake-equation-contributed-to-the-search-for-life-beyond-earth/