Does the Actuality of Life Favor Many Actual Histories?

This essay develops a simple conditional argument for many-history ontologies from the fact that life exists. The question is not why our exact evolutionary sequence occurred, but why reality contains the broad class of life-bearing histories at all. If such histories are sufficiently rare, then a single-history ontology makes the existence of life surprising, while an ontology containing many histories can make it unsurprising. In the limiting case, life may be vanishingly unlikely in any one history while almost certain to occur somewhere if many histories are actualized. Everettian quantum mechanics is a natural candidate for this kind of ontology because its multiplicity is not introduced for anthropic purposes, but arises from taking universal unitary quantum mechanics seriously. The Fermi paradox is discussed as pressure against the claim that life is common within a single history.