from new scientist:
“Zebra finches form monogamous lifetime partnerships, but both males and females indulge in extramarital sex. The benefit for the males is clear: the chance to sire more offspring than fidelity would permit. But why would females cheat when that means risking losing their lifetime partners and catching diseases?
A new study suggests females are promiscuous simply because they inherit many of the same genes responsible for promiscuous behaviour in males.”
the researchers found that both male and female finches who had fathers that had “strayed” were more likely to engage in extrapair copulations themselves. this was the case even when daddy was not around to raise them, so they couldn’t learn the behavior through watching him (the researchers were very sneaky and shuffled eggs between nests!).
from the research article:
“Here we show that in the socially monogamous zebra finch, individual differences in extrapair mating behavior have a hereditary component. Intriguingly, this genetic basis is shared between the sexes, as shown by a strong genetic correlation between male and female measurements of extrapair mating behavior. Hence, positive selection on males to sire extrapair young will lead to increased extrapair mating by females as a correlated evolutionary response. This behavior leads to a fundamentally different view of female extrapair mating: it may exist even if females obtain no net benefit from it, simply because the corresponding alleles were positively selected in the male ancestors.“
“In humans, individual differences in attachment style, fidelity, and sociosexuality are known to have a hereditary basis. The degree to which variation in physiological mechanisms of attachment and of sexual arousal is shared between the sexes is not sufficiently known to predict whether between-sex correlations [like in the finches] can be expected. At the phenotypic level, sexual fidelity correlates with several of the major axes of personality variation (extraversion, agreeableness, and conscientiousness) and, importantly, these correlations are largely consistent between the sexes. The apparent multitude of aspects of personality that may influence sexual fidelity is in agreement with the hypothesis of Halliday and Arnold: such a genetically complex trait would represent a large target for new mutations that would typically have similar (correlated) effects on both sexes.”
in other words, a similar pattern of selection for “infidelity genes” might also be the case in humans (not to mention other animals). maybe.
so, just to be safe, if you’re looking for a mate who will remain faithful, find out how faithful their father was. (especially if you’re a zebra finch.)
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