Coevolution of neocortical size, group size and language in humans

1993 ◽  
Vol 16 (4) ◽  
pp. 681-694 ◽  
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.

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

The Auk ◽  
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.

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

Behaviour ◽  
2016 ◽  
Vol 153 (9-11) ◽  
pp. 1247-1266 ◽  
Author(s):  
T. Czárán ◽  
Duur K. Aanen
Keyword(s):  
Group Size ◽  
Low Frequency ◽  
Evolution Of Cooperation ◽  
Spatially Explicit ◽  
Group Identities ◽  
Limited Dispersal ◽  
Group Members ◽  
Explicit Simulation ◽  
Group Diversity ◽  
Large Groups

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.

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

Behaviour ◽  
2005 ◽  
Vol 142 (11-12) ◽  
pp. 1615-1641 ◽  
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.

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

2014 ◽  
Vol 281 (1789) ◽  
pp. 20140184 ◽  
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.

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

2015 ◽  
Vol 282 (1811) ◽  
pp. 20150954 ◽  
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.

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

2016 ◽  
Vol 371 (1687) ◽  
pp. 20150099 ◽  
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.

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

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.

scholarly journals Fitness of breeders in social Damaraland mole-rats is independent of group size

2021 ◽  
Author(s):  
Jack Thorley ◽  
Hanna Bensch ◽  
Kyle Finn ◽  
Tim Clutton-Brock ◽  
Markus Zöttl
Keyword(s):  
Reproductive Success ◽  
Group Size ◽  
Survival Rates ◽  
Group Living ◽  
Adult Survival ◽  
High Survival ◽  
Successful Reproduction ◽  
Related Group ◽  
Group Members ◽  
Using Data

Damaraland mole-rats (Fukomys damarensis) are usually viewed as an obligatorily group living eusocial species in which successful reproduction is dependent on reproductive altruism of closely related group members. However, the reproductive ecology of social mole-rats in their natural environment remains poorly understood and it is unclear to what extent successful reproduction is dependent on assistance from other group members. Using data from a 7-year field study of marked individuals, we show that, after dispersal from their natal group, individuals typically settled alone in new burrow systems where they enjoyed high survival rates, and often remained in good body condition for several years before finding a mate. Unlike most other eusocial or singular cooperative breeders, we found that Damaraland mole-rats reproduced successfully in pairs without helpers and experimentally formed pairs had the same reproductive success as larger established groups. Overall there was only a weak increase in reproductive success with increasing group size and no effect of group size on adult survival rates across the population. Juveniles in large groups grew faster early in life but their growth rates declined subsequently so that they eventually plateaued at a lower maximum body mass than juveniles from small groups. Taken together, our data suggest that the fitness benefits of group living to breeders are small and we suggest that extended philopatry in Damaraland mole-rats has evolved because of the high costs and constraints of dispersal rather than because of strong indirect benefits accrued through cooperative behaviour.

scholarly journals Pulmonary granuloma is not always the tuberculosis hallmark: pathological findings of different tuberculosis stages in New and Old World Nonhuman Primates naturally infected with the Mycobacterium tuberculosis Complex

2021 ◽  
Author(s):  
Asheley H. B. Pereira ◽  
Claudia A. A. Lopes ◽  
Thalita A. Pissinatti ◽  
Ana C. A. Pinto ◽  
Daniel R. A. Oliveira ◽  
...  
Keyword(s):  
Mycobacterium Tuberculosis ◽  
New World ◽  
Nonhuman Primates ◽  
World Monkey ◽  
Histological Evaluation ◽  
New World Monkeys ◽  
Old World Monkeys ◽  
Pathological Findings ◽  
Old World ◽  
Pulmonary Granuloma

Abstract Herein we present the pathological findings of different tuberculosis stages in Old and New World monkeys kept under human care in Rio de Janeiro, Brazil and naturally infected with Mycobacterium tuberculosis Complex. Fifteen nonhuman primates from five different colonies were incorporated into the study. There are 60% (9/15) Old World Monkeys and 40% (6/15) New World Monkeys. According to the gross and histopathologic findings, the lesions in nonhuman primates of this study are classified into the chronic-active, extrapulmonary, early-activation or latent-reactivation tuberculosis stage. Among the Old World Monkey, 66.7% (6/9) of nonhuman primates, all rhesus monkeys (Macaca mulatta), showed severe granulomatous pneumonia. In all Old World Monkeys cases, typical granulomas were seen in at least one organ regardless of the stage of the disease. In the New World Monkeys, the typical pulmonary granulomas were seen in 16.7% (1/6) of the cases, just in the latent-reactivation stage in Uta Hick’s Bearded Saki (Chiropotes utahickae). In this study, 66.7% (6/9) of Old World Monkeys (OWM) and 83.3% (5/6) of New World Monkeys (NWM) showed pulmonary changes at the histological evaluation. The tuberculosis diagnosis in the nonhuman primates in this study was based on pathological, immunohistochemical, molecular, and bacteriological culture. Although the typical presentation was observed in some cases, the absence of pulmonary granuloma did not exclude the tuberculosis occurrence in nonhuman primates of the Old and New World. Tuberculosis should be included as a cause of interstitial pneumonia with foamy macrophages infiltration in the New World nonhuman primates. Due to the high sensitivity of immunohistochemistry with Anti-Mycobacterium tuberculosis, we suggest the addition of this technique as a diagnostic tool of tuberculosis in the nonhuman primates even when the typical changes are not seen.

Child Development, the Human Group, and Survival

2004 ◽  
Author(s):  
David A. Hamburg ◽  
Beatrix A. Hamburg
Keyword(s):  
Social Life ◽  
Nonhuman Primates ◽  
Human Adaptation ◽  
Old World Monkeys ◽  
Adult Males ◽  
Rapid Progress ◽  
Same Sex ◽  
Natural Habitats ◽  
Continuous Contact ◽  
Males And Females

In the past several decades, the study of the behavior of nonhuman primates—monkeys and apes—has made rapid progress. We can learn from the dimly perceived past when our ancestors confronted the problems of survival without the sophisticated technological aids so inextricably linked to human adaptation in recent times. Our past is inaccessible to direct study. But by careful observation of our closest living relatives, monkeys and apes, we can begin to understand the nonhuman primate heritage from which our ancient ancestors took a long route over millions of years toward humanity. Nonhuman primates live in groups that are held together by strong and enduring bonds between individuals. These bonds may be reflected in a variety of ways: relationships between adult males and females, between adults of the same sex, between juveniles, and between adult males or females and their young. Altogether, in their natural habitats they have a rich social life. Compared with most other mammals, primates have fewer young at a time. Rather than litters, all Old World monkeys and apes have only one offspring at a time, and they give each one a great deal of attention. The young have longer periods of immaturity than other mammals, including prolonged nutritional dependence on the mother. A corollary of the prolonged physical immaturity and nutritional dependence of the primate infant is a longer and more intense mother- infant relationship and a longer period of tutelage and learning the customs and survival skills of the group. In all higher primates except humans, infants cling reflexively to their mothers from birth, and mother-infant contact is maintained virtually all of the time until the much older infant develops the ability to keep up with the mother on its own. Nursing occurs in many short bouts around the clock; in early infancy, it is initiated and terminated by the infant, an easy process, because the infant is always clinging to the mother’s body, anyway. This combination of clinging, carrying, continuous contact, and frequent nursing is characteristic of all higher nonhuman primates.

Sign in / Sign up

Export Citation Format

Share Document