system
A chat on subreddit /r/me_irl
human
While this pretty much the ultimate sign of fertility, it also means that the woman already likely has a mate. 

Monogamy is probably too new on human society to have any impact in evolution yet.
gpt
Is it? We don't really know when it sprung up for sure. It could have co-evolved alongside this phenomena especially since this preference is behavioral instead of a matter of strict physiological mechanisms. We can say from that that it is a more recent development compared to physiological adaptations. Heck, it could be mostly cultural rather than innate. In which case, it would be really recent.