Cooperative breeders do cooperate

Proc. Natl. Acad. Sci. U.S.A.

Fehr

Efferson

et al. 2007

311

314

Human cooperation is unparalleled in the animal world and rests on an altruistic concern for the welfare of genetically unrelated strangers. The evolutionary roots of human altruism, however, remain poorly understood. Recent evidence suggests a discontinuity between humans and other primates because individual chimpanzees do not spontaneously provide food to other group members, indicating a lack of concern for their welfare. Here, we demonstrate that common marmoset monkeys (Callithrix jacchus) do spontaneously provide food to nonreciprocating and genetically unrelated individuals, indicating that other-regarding preferences are not unique to humans and that their evolution did not require advanced cognitive abilities such as theory of mind. Because humans and marmosets are cooperative breeders and the only two primate taxa in which such unsolicited prosociality has been found, we conclude that these prosocial predispositions may emanate from cooperative breeding.cooperative breeding ͉ non-human primates ͉ prosociality ͉ helping ͉ dictator game

Section: Resultsmentioning

confidence: 99%

Other-regarding preferences in a non-human primate: Common marmosets provision food altruistically

Proc. Natl. Acad. Sci. U.S.A.

Fehr

Efferson

et al. 2007

311

314

“…3), are highly responsive to signals from other group members, [38][39][40] and do not appear to punish underperforming helpers. 41 Based on this natural history, one can deduce that callitrichid caregivers have spontaneously prosocial motivations that render them eager to perform acts that benefit others, even in the absence of either solicitation by the recipient, (such as begging or harassment), or expectation of reciprocation.…”

Section: Box 1: Spontaneous Prosociality In Nonhuman Primatesmentioning

confidence: 99%

Cooperative breeding and human cognitive evolution

Evolutionary Anthropology

Hrdy

Schaik³

2009

490

406

Despite sharing a recent common ancestor, humans are surprisingly different from other great apes. The most obvious discontinuities are related to our cognitive abilities, including language, but we also have a markedly different, cooperative breeding system. Among many nonhuman primates and mammals in general, cooperative breeding is accompanied by psychological changes leading to greater prosociality, which directly enhances performance in social cognition. Here we propose that these cognitive consequences of cooperative breeding could have become more pervasive in the human lineage because the psychological changes were added to an ape-level cognitive system capable of understanding simple mental states, albeit mainly in competitive contexts. Once more prosocial motivations were added, these cognitive abilities could also be used for cooperative purposes, including a willingness to share mental states, thereby enabling the emergence of shared intentionality. Shared intentionality has been identified as the original source of many uniquely human cognitive abilities, including cumulative culture and language. Shared intentionality rests on a fundamentally prosocial disposition that is strikingly absent in chimpanzees, but present in cooperatively breeding primates. Thus, our hypothesis is that while chimpanzees and perhaps all great apes exhibit many of the important cognitive preconditions for uniquely human mental capacities to evolve, they lack the psychological preconditions. In humans, we argue, the two components merged, the cognitive component due to common descent from ape ancestors and the motivational component due to convergent evolution of traits typical of many cooperative breeders.As recently as 6 to 7 million years ago, the hominin lineage split off from the rest of the great ape (hominid) lineage 1 and consequently shares many biological traits and behavioral and cognitive similarities with great apes. 2,3Nevertheless, humans also exhibit remarkable differences from our closest relatives. First, we not only live far longer lives and reproduce at faster rates than do the other great apes, but our offspring take much longer to mature and women cease reproduction well before somatic senescence sets in.4 Second, our ecological niche involves specialization on large, valuable food packages that have to be acquired together, as well as shared, and mandatory reliance on techniques acquired through cumulative culture.5 This niche and our social relationships are based on an un-apelike selflessness, a degree of hypersociality reflected in a concern for others, eagerness to share food and information with others, and cooperation in a wide array of contexts, even with nonrelatives and near-strangers.5-8 Our mode of life facilitates our spread into new habitats, resulting in a ubiquitous geographic distribution.9 Third, with regard to intellectual performance, humans differ from the other great apes, which, as a group, show relatively homogeneous cognitive abilities. [10][11][12]

“…Relationships between breeders and helpers may also result in longer periods of acceptance of the helpers in the natal group, or increased allomaternal care by helpers [38,39]. Strong bonds between same-sex helpers may furthermore provide benefits during dispersal [10,40].…”

Section: Accepted Manuscriptmentioning

confidence: 99%

Long-term-stability of relationship structure in family groups of common marmosets, and its link to proactive prosociality

Finkenwirth

2017

Physiology & Behavior

Cooperatively breeding, group-living common marmosets show differentiated relationships, where more strongly bonded dyads within a group engage more in affiliative interactions than less strongly bonded ones. Intriguingly, recent results suggest that strong bonds do not only occur between breeding partners but between individuals from any sex or status, and that strong-bond partners exhibit correlated oxytocin fluctuations (dyadic oxytocin synchrony, OTS) over a period of six weeks. To date, it is unclear whether such relationships are stable over time and whether they are also reflected in higher partner-specific proactive prosociality. To assess the long-term stability of the relationship structure of common marmoset family groups, we investigated whether hormonal and behavioral markers of group structure (dyadic OTS, dyadic affiliation, and individual group integration) in common marmoset families remained stable over a period of six months. We collected baseline urinary OT and social behavior of 36 dyads from three family groups in a non-reproductive period (period A), and again six months later, around the birth of new infants (period B). Patterns of dyadic OTS, dyadic affiliation, and individual group integration were consistent between the two study periods. Oxytocin data from a fourth group (10 dyads), collected in two nonreproductive periods separated by a period of more than five years, could replicate this finding. Furthermore, OTS was also correlated with proactive prosociality that was assessed experimentally for 38 dyads during an earlier study. These results suggest that differentiated relationships are stable over time, even between group members other than the breeding pair, and that more strongly bonded partners also show higher levels of proactive prosociality.Future studies are necessary to identify whether these relationships have an adaptive function, perhaps with regard to positive consequences on cooperativeness.