Humans are traditionally a tournament species but we adopted pair-bonding as a necessity for a functioning society when we implemented civilisation and farming. Cue the birth control pill, social media, online dating and a raft of other cultural changes which freed women from the consequences of unplanned pregnancy and expectations on men to make a good wife out of the woman he got pregnant plus allowed both to explore sexuality with relatively no cost. Now look at what's happening in the dating market, the top tier men have several women on the go, women are chasing and potentially sharing the top tier men and most men are getting little to no attention.