Continued...

Current molecular clock analyses of bacterial origins point to c. 2.5 Gya = perhaps a late arrival is the simplest explanation.

If so it changes Dr Charles Lineweaver's recent analysis quite dramatically...

http://au.arxiv.org/abs/astro-ph/0209385

http://au.arxiv.org/abs/astro-ph/0205014

...if life arose in 200 myr, in his analysis, then its probability of arising after 1 Gyr is >33%. BUT if the wait time is >2 Gyr, then this probability is a LOT smaller AFAIK. Say <3% ?

Could easily explain the Fermi paradox?

BUT the jury is still out on early life... 0.2 Gyr or 2 Gyr???

Actually if it might've arisen after 4.3 Gya, but didn't arrive until 3.5 Gya, that's 0.8 Gyr... HMMM....