Like many other mammalian and primate societies [1-4], humans are said to live in
multilevel social groups, with individuals situated in a series of hierarchically
structured sub-groups [5, 6]. Although this multilevel social organization has been
described among contemporary hunter-gatherers [5], questions remain as to the benefits
that individuals derive from living in such groups. Here, we show that food sharing
among two populations of contemporary hunter-gatherers-the Palanan Agta (Philippines)
and Mbendjele BaYaka (Republic of Congo)-reveals similar multilevel social structures,
with individuals situated in households, within sharing clusters of 3-4 households,
within the wider residential camps, which vary in size. We suggest that these groupings
serve to facilitate inter-sexual provisioning, kin provisioning, and risk reduction
reciprocity, three levels of cooperation argued to be fundamental in human societies
[7, 8]. Humans have a suite of derived life history characteristics including a long
childhood and short inter-birth intervals that make offspring energetically demanding
[9] and have moved to a dietary niche that often involves the exploitation of difficult
to acquire foods with highly variable return rates [10-12]. This means that human
foragers face both day-to-day and more long-term energetic deficits that conspire
to make humans energetically interdependent. We suggest that a multilevel social organization
allows individuals access to both the food sharing partners required to buffer themselves
against energetic shortfalls and the cooperative partners required for skill-based
tasks such as cooperative foraging.