Throughout most of history, and likely a great deal of prehistory, kin have had a substantial influence on human mate selection. This makes humans unique. It also means that simple Darwinian sexual selection models that apply to other species may not work as well with humans. Male kin had more influence than female kin; and female maters were more subject to kin influence than male. But there was significant influence on both genders by members of both genders.

Kin and mating principals did not have perfectly aligned interests. For example, Good Genes (GG) (appearance and some social skill/charisma) preferences were likely stronger in the principals than the kin, and the lineage of the principals was more impacted. Furthermore, it is likely that principals evolved adaptations to better assert their interests (better parental manipulation, etc.) and kind adapted to better protect their own preferences.

In the evolutionary novel modern West, we have not only seen the sudden depreciation of the value of male Provisioning, Protection and Parental Investment (PPP) traits. We have also seen the sudden end of kin influence. The consequences of the latter are rarely discussed, particularly in evolutionary terms.