What makes people care? An anthropologist’s view of Biocultural Reproduction — the human style of hyper-cooperation

The essence of Being Human is the practice of Biocultural Reproduction (BCR).  BCR is defined as the set of marriage and kinship based rules for extra-maternal cooperation in the production, feeding, and care of offspring. Human evolution theory needs to explain how people successfully combined a vastly extended period of offspring dependency and delayed reproduction with helpless newborns — with large heads and much body fat (even with problems giving birth) -- a short duration of breast-feeding, an adolescent growth spurt, and vigorous post-menopause valuable grandmothers. Are these characteristics a package or a mosaic?