Is there anybody out there? (Forwarded)

Communications Office
University of East Anglia
Norwich, U.K.

Contact:
Cat Bartman, 44-016-035-93007

16 April 2008

Is there anybody out there?

Is there anybody out there? Probably not, according to a scientist from the
University of East Anglia. A mathematical model produced by Prof Andrew
Watson suggests that the odds of finding new life on other Earth-like
planets are low, given the time it has taken for beings such as humans to
evolve and the remaining life span of Earth.

Structurally complex and intelligent life evolved late on Earth and it has
already been suggested that this process might be governed by a small number
of very difficult evolutionary steps.

Prof Watson, from the School of Environmental Sciences, takes this idea
further by looking at the probability of each of these critical steps
occurring in relation to the life span of Earth, giving an improved
mathematical model for the evolution of intelligent life.

According to Prof Watson a limit to evolution is the habitability of Earth,
and any other Earth-like planets, which will end as the sun brightens. Solar
models predict that the brightness of the sun is increasing, while
temperature models suggest that because of this the future life span of
Earth will be 'only' about another billion years, a short time compared to
the four billion years since life first appeared on the planet.

"The Earth's biosphere is now in its old age and this has implications for
our understanding of the likelihood of complex life and intelligence arising
on any given planet," said Prof Watson.

"At present, Earth is the only example we have of a planet with life. If we
learned the planet would be habitable for a set period and that we had
evolved early in this period, then even with a sample of one, we'd suspect
that evolution from simple to complex and intelligent life was quite likely
to occur. By contrast, we now believe that we evolved late in the habitable
period, and this suggests that our evolution is rather unlikely. In fact,
the timing of events is consistent with it being very rare indeed."

Prof Watson suggests the number of evolutionary steps needed to create
intelligent life, in the case of humans, is four. These probably include the
emergence of single-celled bacteria, complex cells, specialized cells
allowing complex life forms, and intelligent life with an established
language.

"Complex life is separated from the simplest life forms by several very
unlikely steps and therefore will be much less common. Intelligence is one
step further, so it is much less common still," said Prof Watson.

His model, published in the journal Astrobiology, suggests an upper limit
for the probability of each step occurring is 10 per cent or less, so the
chances of intelligent life emerging is low -- less than 0.01 per cent over
four billion years.

Each step is independent of the other and can only take place after the
previous steps in the sequence have occurred. They tend to be evenly spaced
through Earth's history and this is consistent with some of the major
transitions identified in the evolution of life on Earth.