The early evolution of cooperation in humans. On cheating, group identity and group size

The evolution of cooperation is difficult to understand, because cheaters — individuals who profit without cooperating themselves — have a benefit in interaction with cooperators. Cooperation among humans is even more difficult to understand, because cooperation occurs in large groups, making cheating a bigger threat. Restricting cooperation to members of one’s own group based on some tag-based recognition of non-group members (allorecognition) has been shown to stabilise cooperation. We address how spatial structure and group size affect the opportunities for cheating such tag-based cooperation in a spatially explicit simulation. We show that increased group diversity, under conditions of limited dispersal, reduces the selective opportunities for cheaters. A small number can already be sufficient to keep cheating at a low frequency. We discuss how marginal additional benefits of increased group size, above the benefits of local cooperation, can provide the selective pressure to reduce the number of group identities and discuss possible examples.

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Coevolution of neocortical size, group size and language in humans

Behavioral and Brain Sciences ◽

10.1017/s0140525x00032325 ◽

1993 ◽

Vol 16 (4) ◽

pp. 681-694 ◽

Cited By ~ 957

Author(s):

R. I. M. Dunbar

Keyword(s):

Group Size ◽

Nonhuman Primates ◽

Old World Monkeys ◽

Time Sharing ◽

Social Grooming ◽

Historical Societies ◽

Behavioural Characteristics ◽

Personal Experiences ◽

Group Members ◽

Large Groups

AbstractGroup size covaries with relative neocortical volume in nonhuman primates. This regression equation predicts a group size for modern humans very similar to that for hunter-gatherer and traditional horticulturalist societies. Similar group sizes are found in other contemporary and historical societies. Nonhuman primates maintain group cohesion through social grooming; among the Old World monkeys and apes, social grooming time is linearly related to group size. Maintaining stability of human-sized groups by grooming alone would make intolerable time demands. It is therefore suggested (1) that the evolution of large groups in the human lineage depended on developing a more efficient method for time-sharing the processes of social bonding and (2) that language uniquely fulfills this requirement. Data on the size of conversational and other small interacting groups of humans accord with the predicted relative efficiency of conversation compared to grooming as a bonding process. In human conversations about 60% of time is spent gossiping about relationships and personal experiences. Language may accordingly have evolved to allow individuals to learn about the behavioural characteristics of other group members more rapidly than was feasible by direct observation alone.

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Does Group Size Affect Field Metabolic Rate of Arabian Babbler (Turdoides squamiceps) Nestlings?

The Auk ◽

10.1093/auk/118.2.525 ◽

2001 ◽

Vol 118 (2) ◽

pp. 525-528

Author(s):

Avner Anava ◽

Michael Kam ◽

Amiram Shkolnik ◽

A. Allan Degen

Keyword(s):

Metabolic Rate ◽

Group Size ◽

Annual Number ◽

Field Metabolic Rate ◽

Negative Effect ◽

Group Feeding ◽

Group Members ◽

Single Nest ◽

Large Groups ◽

Arabian Babbler

Abstract Arabian Babblers (Turdoides squamiceps) are territorial, cooperative breeding passerines in which groups consist of parents and helpers. All members of the group feed nestlings in a single nest and all group members provision at similar rates. We hypothesized that the field metabolic rate (FMR) of Arabian Babbler nestlings is related to group feeding; that is, FMR would be greater in nestlings of larger rather than smaller sized groups. To test that hypothesis, we measured FMR of 10 day old nestlings from small (2 and 3 individuals), medium (4 and 5 individuals), and large (6 or more individuals) groups. We also determined number of hatchlings and fledglings produced per group. There was an increase in body mass and FMR from small to medium-sized groups, but there was a levelling off or decrease in those parameters in large groups. That suggests that there is an optimum group number for provisioning nestlings, above which there may be a negative effect. The relationship between group size and annual number of eggs was not significant, but there was a positive and linear relationship between group size and annual fledglings production. Thus, more eggs reached the fledgling stage with an increase in group size, suggesting that larger groups are better able to defend the nest against predators.

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Large group size yields group stability in the cooperatively breeding cichlid Neolamprologus pulcher

Behaviour ◽

10.1163/156853905774831891 ◽

2005 ◽

Vol 142 (11-12) ◽

pp. 1615-1641 ◽

Cited By ~ 87

Author(s):

Michael Taborsky ◽

Lyanne Brouwer ◽

Dik Heg ◽

Zina Bachar

Keyword(s):

Group Size ◽

The Body ◽

Female Size ◽

Neolamprologus Pulcher ◽

Large Group ◽

Cooperatively Breeding ◽

Group Members ◽

One Year ◽

Large Groups

AbstractGroup size has been shown to positively influence survival of group members in many cooperatively breeding vertebrates, including the Lake Tanganyika cichlid Neolamprologus pulcher, suggesting Allee effects. However, long-term data are scarce to test how these survival differences translate into changes in group extinction risk, group size and composition. We show in a field study of 117 groups from six different colonies (three from two populations each), that group size critically influences these parameters between years. Within one year, 34% of the groups went extinct. Group size correlated positively between years and large groups did not go extinct. The latter were more likely to contain small helpers the subsequent year, which is a cumulative measure of the previous months' reproductive success. Finally, there was a tendency that large groups were more likely to contain a breeding male and female still a year after the first check. The breeder male size, breeder female size, and largest helper size did not influence these parameters, and also did not correlate with the sizes of these categories of fish after one year. This suggests that group size, and not the body size or fighting ability of group members, was the critical variable determining the success of groups. In total, seven groups had fused with other groups between years. To our knowledge, this is the first study showing long-term benefits of large group size in a cooperatively breeding fish. We discuss the importance of differential survival and dispersal of group members for the demonstrated group size effects.

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Group-size-dependent punishment of idle subordinates in a cooperative breeder where helpers pay to stay

Proceedings of The Royal Society B Biological Sciences ◽

10.1098/rspb.2014.0184 ◽

2014 ◽

Vol 281 (1789) ◽

pp. 20140184 ◽

Cited By ~ 57

Author(s):

Stefan Fischer ◽

Markus Zöttl ◽

Frank Groenewoud ◽

Barbara Taborsky

Keyword(s):

Group Size ◽

Small Groups ◽

Cooperative Breeding ◽

Breeding Systems ◽

Idle Period ◽

Cognitive Constraints ◽

Size Dependent ◽

Cooperatively Breeding ◽

Group Members ◽

Large Groups

In cooperative breeding systems, dominant breeders sometimes tolerate unrelated individuals even if they inflict costs on the dominants. According to the ‘pay-to-stay’ hypothesis, (i) subordinates can outweigh these costs by providing help and (ii) dominants should be able to enforce help by punishing subordinates that provide insufficient help. This requires that dominants can monitor helping and can recognize group members individually. In a field experiment, we tested whether cooperatively breeding cichlid Neolamprologus pulcher subordinates increase their help after a forced ‘idle’ period, how other group members respond to a previously idle helper, and how helper behaviour and group responses depend on group size. Previously idle helpers increased their submissiveness and received more aggression than control helpers, suggesting that punishment occurred to enforce help. Subordinates in small groups increased their help more than those in large groups, despite receiving less aggression. When subordinates were temporarily removed, dominants in small groups were more likely to evict returning subordinates. Our results suggest that only in small groups do helpers face a latent threat of punishment by breeders as predicted by the pay-to-stay hypothesis. In large groups, cognitive constraints may prevent breeders from tracking the behaviour of a large number of helpers.

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Reproductive sharing in relation to group and colony-level attributes in a cooperative breeding fish

Proceedings of The Royal Society B Biological Sciences ◽

10.1098/rspb.2015.0954 ◽

2015 ◽

Vol 282 (1811) ◽

pp. 20150954 ◽

Cited By ~ 21

Author(s):

Jennifer K. Hellmann ◽

Isaac Y. Ligocki ◽

Constance M. O'Connor ◽

Adam R. Reddon ◽

Kelly A. Garvy ◽

...

Keyword(s):

Group Size ◽

Spatial Scales ◽

Model Species ◽

Cooperatively Breeding ◽

Group Members ◽

Males And Females ◽

Territory Density ◽

Large Groups ◽

Colony Level ◽

Group Size And Composition

The degree to which group members share reproduction is dictated by both within-group (e.g. group size and composition) and between-group (e.g. density and position of neighbours) characteristics. While many studies have investigated reproductive patterns within social groups, few have simultaneously explored how within-group and between-group social structure influence these patterns. Here, we investigated how group size and composition, along with territory density and location within the colony, influenced parentage in 36 wild groups of a colonial, cooperatively breeding fish Neolamprologus pulcher . Dominant males sired 76% of offspring in their group, whereas dominant females mothered 82% of offspring in their group. Subordinate reproduction was frequent, occurring in 47% of sampled groups. Subordinate males gained more paternity in groups located in high-density areas and in groups with many subordinate males. Dominant males and females in large groups and in groups with many reproductively mature subordinates had higher rates of parentage loss, but only at the colony edge. Our study provides, to our knowledge, the first comprehensive quantification of reproductive sharing among groups of wild N. pulcher , a model species for the study of cooperation and social behaviour. Further, we demonstrate that the frequency of extra-pair parentage differs across small social and spatial scales.

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A simple rule for the evolution of contingent cooperation in large groups

Philosophical Transactions of the Royal Society B Biological Sciences ◽

10.1098/rstb.2015.0099 ◽

2016 ◽

Vol 371 (1687) ◽

pp. 20150099 ◽

Cited By ~ 8

Author(s):

Roberto H. Schonmann ◽

Robert Boyd

Keyword(s):

Group Size ◽

Simple Formula ◽

Large Scale ◽

Structured Populations ◽

Cooperative Behaviour ◽

Human Lineage ◽

Contingent Reward ◽

Wide Range ◽

Group Members ◽

Large Groups

Humans cooperate in large groups of unrelated individuals, and many authors have argued that such cooperation is sustained by contingent reward and punishment. However, such sanctioning systems can also stabilize a wide range of behaviours, including mutually deleterious behaviours. Moreover, it is very likely that large-scale cooperation is derived in the human lineage. Thus, understanding the evolution of mutually beneficial cooperative behaviour requires knowledge of when strategies that support such behaviour can increase when rare. Here, we derive a simple formula that gives the relatedness necessary for contingent cooperation in n -person iterated games to increase when rare. This rule applies to a wide range of pay-off functions and assumes that the strategies supporting cooperation are based on the presence of a threshold fraction of cooperators. This rule suggests that modest levels of relatedness are sufficient for invasion by strategies that make cooperation contingent on previous cooperation by a small fraction of group members. In contrast, only high levels of relatedness allow the invasion by strategies that require near universal cooperation. In order to derive this formula, we introduce a novel methodology for studying evolution in group structured populations including local and global group-size regulation and fluctuations in group size.

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Effect of the group size on the evolution of cooperation when an exit option is present

Journal of Theoretical Biology ◽

10.1016/j.jtbi.2021.110678 ◽

2021 ◽

pp. 110678

Author(s):

Shun Kurokawa

Keyword(s):

Group Size ◽

Evolution Of Cooperation ◽

Exit Option

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Does crossing the road in a group influence pedestrians’ gaze behavior?

Proceedings of the Human Factors and Ergonomics Society Annual Meeting ◽

10.1177/1071181320641467 ◽

2020 ◽

Vol 64 (1) ◽

pp. 1938-1942

Author(s):

Mirjam Lanzer ◽

Martin Baumann

Keyword(s):

Group Size ◽

Situational Factors ◽

Gaze Behavior ◽

The Road ◽

Road Users ◽

Gender Influence ◽

Vulnerable Road Users ◽

Group Members ◽

And Gender ◽

Group Characteristics

So far, research on pedestrians’ gaze behavior while crossing roads has mainly focused on individual pedestrians rather than groups. However, pedestrians often travel in groups especially in downtown areas. This observational study investigated how group characteristics (group size and movement of the group), situational factors (presence of traffic), and demographic variables (age and gender) influence pedestrians’ gaze behavior towards traffic during road crossing. A total of N = 197 pedestrians were observed of whom n = 24 traveled alone, n = 128 traveled in groups of two or three, and n = 45 traveled in groups of four or more. Results indicated that with increasing group size, the odds to observe traffic decreased. Diffusion of responsibility among group members might explain this effect. Finally, pedestrians’ group characteristics should be considered when developing automated vehicles that interact with vulnerable road users.

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