Humans may extend kin-based sharing rules to strangers by treating them as context-dependent relatives.

Evidence

A social index is not the same thing as a WRT, because the latter applies to sympathetic preferences, as exemplified by Hamilton’s (1963) notion of inclusive fitness. However, one can speculate that our species may have graduated from using Hamilton’s rule within the family to using social indices more generally via the expedient of resolving sharing problems by treating strangers as though they were relatives, with the degree of relationship determined by the context in which the sharing problem arises. — Nicolas Baumard, A mutualistic approach to morality, 285

Categorization

• XREF: Connects directly to the reader’s Big God / moral cognition framework of the priests-sacrifice analysis, and to the ritual-context framing of partner choice. Treating strangers as context-dependent relatives is essentially what high-stakes moral environments compel. — connects to: Sharing develops later and less spontaneously than helping or comforting. — Nicolas Baumard, A mutualistic approach to morality: The…, 382; Kin selection arises from helping related individuals reproduce; Trust extends kin-group loyalty outward to the whole society (+3 more)
• ADDENDUM: Relevant to ‘On Sacrifice’ — the mechanism by which sacrificial/moral commitment extends beyond kin to strangers in high-stakes contexts complements the stabilizing-ritual thesis.

Related

• Sharing develops later and less spontaneously than helping or comforting. (similarity 0.81)
• Kinship provides reliable trust bonds regardless of personal sympathy. (similarity 0.78)

Broader Connections

• Kin selection arises from helping related individuals reproduce #expands (0.85)
• Trust extends kin-group loyalty outward to the whole society #qualifies (0.80)
• Morality extends beyond fairness among strangers to relational obligations #expands (0.75) — Nicolas Baumard, A mutualistic approach to morality, 333
• Kinship-based trust fails when its sanctioning institutions do not migrate #qualifies (0.75)