this 'well they are naturally better caregivers' ONLY applies in a society that follows natural instincts.

Recent phenomenon, actually. Active effort by the first wave in order to gain stronger standings in family courts, prior to them, it was de facto assumed that men, the primary caregivers of women AND children in those times, "clearly" had more practice and skill in caregiving, rather than the women, who they thus viewed as a group that needed caregiving/providing for, not a caregiver necessarily in and of themselves.