Editing Falsifiability (section)

===Natural selection===

{{Main| Survival of the fittest#Tautology}}
In the 5th and 6th editions of ''[[On the Origin of Species]]'', following a suggestion of [[Alfred Russel Wallace]], Darwin used "Survival of the fittest", an expression first coined by [[Herbert Spencer]], as a synonym for "Natural Selection".<ref name="naturalselectionassurvivalofthefittest" group=upper-alpha /> Popper and others said that, if one uses the most widely accepted definition of "fitness" in modern biology (see subsection {{slink||Evolution}}), namely reproductive success itself, the expression "survival of the fittest" is a tautology.<ref name="thompsonnaturalselectionastautology" group=upper-alpha /><ref name="naturalselectionasatautology" group=upper-alpha /><ref name="poppernaturalselectiontautological" group=upper-alpha />

Darwinist [[Ronald Fisher]] worked out mathematical theorems to help answer questions regarding natural selection. But, for Popper and others, there is no (falsifiable) law of Natural Selection in this, because these tools only apply to some rare traits.<ref name="thompsonnotalltraitsaffectfitness" group=upper-alpha /><ref name="poppernotalltraitsaffectfitness" group=upper-alpha /> Instead, for Popper, the work of Fisher and others on Natural Selection is part of an important and successful metaphysical research program.{{sfn|Elgin|Sober|2017}}