&gt; It probably relates because the marriages themselves don&#x27;t matter, it is the family that forms and the impacts that has on individuals that do.<p>That&#x27;s speculative, and not at all what the study found.<p>It <i>could</i> be that that&#x27;s what&#x27;s important; it could be, instead, that what is important is the social expectation of marriage combined with the opportunities available for it. It could be something else. It could be a combination of any of the three.<p>&gt; Thus if you had some society which allowed only monogamy but also allowed concubines, you would likely see the same issues as caused by polygamy.<p>Since concubinage is generally exclusive in the same way as marriage is (and exclusive of marriage), you&#x27;d expect in pretty much any case it to have similar social effects to polygyny (if it isn&#x27;t just considered a <i>form</i> of polygyny in which there is a wife with a formally preferred status, which is common in polygyny.)<p>&gt; Or if you had a society that didn&#x27;t do marriage at all, but the relationships that formed tended to be greater towards polygamy than monogamy.<p>OTOH, if it is the social expectation and opportunity aspect of marriage that is at issue, a society which lacked the formal marriage and social expectations tied to it might not have the problems of a formally polygynous society <i>even if</i> the informal relations formed were generally polgynous rather than monogamous.<p>And if, on yet <i>another</i> hand, there is a stabilizing effect of socially-recognized relationship, the absence of social recognition might produce problems similar to those in a formally polygynous society <i>regardless</i> of the form of the informal relationships that form.