Overview
- On average about 66% of human offspring are full siblings, placing humans 7th of 35 mammals between the Eurasian beaver (~73%) and the white‑handed gibbon (~64%).
- The research drew on genetic sibling data from more than 100 historical and contemporary human societies plus 34 other mammal species, incorporating ancient DNA where available.
- Only about nine percent of mammal species qualify as monogamous by this measure, with higher examples including the California mouse (100%), African wild dog (~85%) and Damaraland mole‑rat (~79%).
- Human full‑sibling rates vary sharply across contexts, from roughly 26% at some Neolithic sites to as high as 100% in others.
- The author cautions that the metric captures reproduction rather than sexual exclusivity, notes incomplete data, and suggests widespread monogamy may have fostered large kin networks and complex societies.