Hi All

The current New Scientist has an article by Jon Copley which discusses the recent sceptical reassessment of the earliest evidences of life on Earth. Martin Brasier from Oxford University and a number of other researchers have questioned Bill Schopf's microfossils from 3.5 Gya.

Seems the "sedimentary rock" they are found in isn't. It's an intrusive mineral which produces streaks of carbon they sometimes looks like cells. Schopf has used Raman-spectroscopy to analysis the "microfossils" and claims they are legit, but others have shown how the "bio-signature" can be mimicked abiotically.

Brasier suggests the only uneqivocal microfossils date from 1.9 Gya - though personally he suspects life arose c. 3.5 Gya. It's just that the current "evidence" has alternative explanations. Even the late Archean bio-markers from 2.7 Gya might have alternative explanations.

Now what if...

what if life really did only arise c. 2.5 Gya - just before the oxygen spike that terminated the Archean. That gives 2.3 Gyr for abiogenesis, which in turn suggests a lower probability for life arising. Life could have arisen anytime from 4.3 Gya according to current guesstimates - IF it delayed 2 Gyr...