Establishing the Criteria for Early Life on Earth
A significant but widely ignored problem in early life studies concerns our reliance upon inductive lines of reasoning. More specifically, there has tended to be too much reliance upon evidence that is ‘consistent with’ microbes, without falsifying or rejecting (sensu Popper, 1959) other possible non-biological scenarios that may likewise be consistent. We have tended to ask ‘what do these structures remind us of’, rather than ‘what are these structures’? Recognition of the need for testing a null hypothesis of a non-biological origin for the earliest fossil evidence therefore forces us to face up to, and overcome, this very human tendency. Arguments of the kind: ‘absence of evidence is not evidence of absence’ are also highly insecure in the high-stakes search for early life, and are incompatible with evolutionary studies of all kinds.
Attempts have been made to establish sets of more rigid criteria that any claims for early life should adhere to. These are here divided into criteria used to demonstrate the antiquity of a given structure and those used to demonstrate the biogenicity of a structure.
KeywordsAgate Sedimentation Geochemistry Fractionation Pyrite
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