Cheating
For this dynamic and the practicality of enjoying the best of both genetic worlds, women find it necessary to 'cheat'. This cheating can be done proactively or reactively.
In the reactive model, a woman who has already paired with her long term partner choice, engages in an extramarital or outside-pairing, sexual intercourse with a short term partner (i.e. the classic cheating wife or girlfriend). That's not to say this short term opportunity cannot develop into a 2nd, long term mate, but the action itself is a method for securing better genetic stock (by her perception) than the committed male provider is capable of supplying.
Proactive cheating is the single Mommy dillema. This form of 'cheating' relies on the woman breeding with a Good Genes male, bearing his children and then abandoning him, or having him abandon her, (again through invented social conventions) in order to find a Good Dad male to provide for her and the children of her Good Genes partner to ensure their security. The feminine facilitates this through invented social mores that positively affirm a man for "stepping up to the plate" and helping the "poor woman victimized by the villainous ex" share in a parental investment that was never his burden.
I want to stress again that (most) women do not have some consciously recognized, master plan to enact this cycle and deliberately trap men into it. Rather the motivations for this behavior and the accompanying rationales invented to justify it are an unconscious process. It's my belief that for the most part, women are unaware of this dynamic, but are nonetheless subject to it's influence. For a female of any species to facilitate a methodology for breeding with the best genetic partner she's able to attract AND to ensure her own and her offspring's survival by pairing with the best provisioning partner; this is an evolutionary jackpot.