The assumption that natural selection was the cause of a specific phenomenon is something that is not, and cannot be, tested – because this assumption is outside science, comes before science, structures scientific investigations.
Paradoxically, it is the metaphysical – hence extra-scientific – nature of the concept of natural selection which enables it to serve as a kind of substitute for religion.
This is because natural selection is assumed to be the explanation for phenomena in general – therefore once this metaphysical assumption has been made, once natural selection has been accepted as universally valid, then all further experiences and investigations are structured by this assumption.
Therefore the ‘truth’ of natural selection is, apparently, reinforced by anything and everything which happens from that point onwards; natural selection can never fail to explain anything, because all valid explanations are required to conform to natural selection.
Excerpt from Bruce Charlton’s blog post “Natural Selection as Religion“, August 29, 2013.