As long as we’re speculating...
If a woman is in a group/society/tribe where a monogamous relationship is not the guarantee of long term protection and sustenance, her alternatives are limited to being able to go it alone, or being able to keep the attention of multiple partners for fractional support from each.
She’d better be good at it, or she will starve in her old age.
People are only truly good at things they enjoy...
Take a look at our "inner cities" for an example of this. Women having babies from multiple different men, most of them thugs. Being under the protection of a thug shields her from all the OTHER thugs of the neighborhood. Having multiple thugs gives her spare thugs if one gets shot or goes to prison. This is only viable, though, if she has an independent source of support, because the thug boyfriends do not contribute income (rather, they consume).
In a society where monogamous relationships are not strongly backed by law and custom, most of the women will spend their attractive years competing with each other chasing a relatively small number of the most desirable men. These men will move on when a women stops being as attractive as her competition. Marriage and monogamy was likely invented by women, as a means to secure the support of a man past the point where the woman loses her maidenly looks.