> This probably happened only once in history and under
> very specific conditions, which are very unlikely to be
> repeated.
"Anything not forbidden is compulsory" only if you assume an infinitely long time horizon
Without having more data points, it is hard to say whether the average life span of a planet in the Universe is long enough for multicellular life to inevitably develop.
So far, all evidence points to no. It is also true, however, that so far we have negligible data.
Re:UN to appoint Earth contact for aliens
by carbocation on Monday September 27, 2010 @01:08AM
(#1730803)
Wolbachia has a remarkable relationship, with some species dependent upon it for fertility. I'd say that endosymbiosis has occurred independently a few times.
A book called "Power, Sex, Suicide: Mitochondria and the Meaning of Life" provides some insights. The author argues that the only reason multicellular organisms evolved is that one type of cells ("host") engulfed (or engaged into symbiotic relationship with) another, that became mitochondria and was used as a "power plant". This probably happened only once in history and under very specific conditions, which are very unlikely to be repeated.