Intelligent ET life probably not likely, according to English study

William Atkins
Saturday, 12 April 2008 21:56

Science - Space

New planets around other stars (called extrasolar planets or exoplanets) are being discovered all of the time by astronomers, however, a new mathematical study by an English environmental scientist states that intelligent extraterrestrial (ET) life in the universe is “probably rare.”


As of April 2008, 287 exoplanets have been detected by scientists. No doubt countless others are out there that haven’t yet been (or, are unable to be) detected by astronomers using our current technologies of ground-based and space-based telescopes.

Andrew J. Watson, from the School of Environmental Science, University of East Anglia (Norwich, United Kingdom), has stated--based on a mathematical model he developed--that even if some of these exoplanets turn out to be Earth-like, the chances that they contain intelligent life is very small.

Watson’s results are published in the February 1, 2008 issue of the journal Astrobiology . Its title is “Implications of an Anthropic Model of Evolution for Emergence of Complex Life and Intelligence.”

Watson’s abstract to the paper states, “Structurally complex life and intelligence evolved late on Earth; models for the evolution of global temperature suggest that, due to the increasing solar luminosity, the future life span of the (eukaryote) biosphere will be “only” about another billion years, a short time compared to the 4 Ga since life began.”

He continues “A simple stochastic model … suggests that this timing might be governed by the necessity to pass a small number, n, of very difficult evolutionary steps, with n < 10 and a best guess of n = 4, in order for intelligent observers like ourselves to evolve.”

Also, “Here I extend the model analysis to derive probability distributions for each step. Past steps should tend to be evenly spaced through Earth's history, and this is consistent with identification of the steps with some of the major transitions in the evolution of life on Earth. A complementary approach, identifying the critical steps with major reorganizations in Earth's biogeochemical cycles, suggests that the Archean-Proterozoic and Proterozoic-Phanerozoic transitions might be identified with critical steps.”

And, in conclusion, “The success of the model lends support to a “Rare Earth” hypothesis … structurally complex life is separated from prokaryotes by several very unlikely steps and, hence, will be much less common than prokaryotes. Intelligence is one further unlikely step, so it is much less common still.”

Watson's four discrete steps for the evolution of intellient life is provided on the next page.