Aggressive interactions influence cognitive performance in Western Australian magpies.

Extensive research has investigated the relationship between the social environment and cognition, suggesting that social complexity may drive cognitive evolution and development. However, evidence for this relationship remains equivocal. Group size is often used as a measure of social complexity, but this may not capture intraspecific variation in social interactions. Social network analysis can provide insight into the cognitively demanding challenges associated with group living at the individual level. Here, we use social networks to investigate whether the cognitive performance of wild Western Australian magpies (Gymnorhina tibicen dorsalis) is related to group size and individual social connectedness. We quantified social connectedness using four interaction types: proximity, affiliative, agonistic and vocal. Consistent with previous research on this species, individuals in larger groups performed better on an associative learning task. However, social network position was also related to cognitive performance. Individuals receiving aggressive interactions performed better, while those involved in aggressive interactions with more group members performed worse. Overall, this suggests that cognitive performance is related to specific types of social interaction. The findings from this study highlight the value of considering fine-grained metrics of sociality that capture the challenges associated with social life when testing the relationship between the social environment and cognition.

Long-Read Genome Sequencing Provides Molecular Insights into Scavenging and Societal Complexity in Spotted Hyena Crocuta crocuta.

The spotted hyena (Crocuta crocuta) is a large and unique terrestrial carnivore. It is a particularly fascinating species due to its distinct phenotypic traits, especially its complex social structure and scavenging lifestyle, with associated high dietary exposure to microbial pathogens. However, the underlying molecular mechanisms related to these phenotypes remain elusive. Here, we sequenced and assembled a high-quality long-read genome of the spotted hyena, with a contig N50 length of ∼13.75 Mb. Based on comparative genomics, immunoglobulin family members (e.g., IGKV4-1) showed significant adaptive duplications in the spotted hyena and striped hyena. Furthermore, immune-related genes (e.g., CD8A, LAG3, and TLR3) experienced species-specific positive selection in the spotted hyena lineage. These results suggest that immune tolerance between the spotted hyena and closely related striped hyena has undergone adaptive divergence to cope with prolonged dietary exposure to microbial pathogens from scavenging. Furthermore, we provided the potential genetic insights underlying social complexity, hinting at social behavior and cognition. Specifically, the RECNE-associated genes (e.g., UGP2 and ACTR2) in the spotted hyena genome are involved in regulation of social communication. Taken together, our genomic analyses provide molecular insights into the scavenging lifestyle and societal complexity of spotted hyenas.

Inter-group alliance dynamics in Indo-Pacific bottlenose dolphins (Tursiops aduncus).

The social intelligence hypothesis holds that complex social relationships are the major selective force underlying the evolution of large brain size and intelligence. Complex social relationships are exemplified by coalitions and alliances that are mediated by affiliative behavior, resulting in differentiated but shifting relationships. Male Indo-Pacific bottlenose dolphins in Shark Bay, Australia, form three alliance levels or 'orders', primarily among non-relatives. Strategic alliance formation has been documented within both first- and second-order alliances and between second-order alliances ('third-order alliances'), revealing that the formation of strategic inter-group alliances is not limited to humans. Here we conducted a fine-scale study on 22 adult males over a 6-year period to determine if third-order alliance relationships are differentiated, and mediated by affiliative interactions. We found third-order alliance relationships were strongly differentiated, with key individuals playing a disproportionate role in maintaining alliances. Nonetheless, affiliative interactions occurred broadly between third-order allies, indicating males maintain bonds with third-order allies of varying strength. We also documented a shift in relationships and formation of a new third-order alliance. These findings further our understanding of dolphin alliance dynamics and provide evidence that strategic alliance formation is found in all three alliance levels, a phenomenon with no peer among non-human animals.

Slow development of vocal sequences through ontogeny in wild chimpanzees (Pan troglodytes verus).

The development of the unique, hierarchical, and endless combinatorial capacity in a human language requires neural maturation and learning through childhood. Compared with most non-human primates, where combinatorial capacity seems limited, chimpanzees present a complex vocal system comprising hundreds of vocal sequences. We investigated how such a complex vocal system develops and the processes involved. We recorded 10,929 vocal utterances of 98 wild chimpanzees aged 0-55 years, from Taï National Park, Ivory Coast. We developed customized Generalized non-Linear Models to estimate the ontogenetic trajectory of four structural components of vocal complexity: utterance length, diversity, probability of panting (requiring phonation across inhalation and exhalation), and probability of producing two adjacent panted units. We found chimpanzees need 10 years to reach adult levels of vocal complexity. In three variables, the steepest increase coincided with the age of first non-kin social interactions (2-5 years), and plateaued in sub-adults (8-10 years), as individuals integrate into adult social life. Producing two adjacent panted units may require more neuromuscular coordination of the articulators, as its emergence and steepest increase appear later in development. These results suggest prolonged maturational processes beyond those hitherto thought likely in species that do not learn their vocal repertoire. Our results suggest that multifaceted ontogenetic processes drive increases in vocal structural complexity in chimpanzees, particularly increases in social complexity and neuro-muscular maturation. As humans live in a complex social world, empirical support for the "social complexity hypothesis" may have relevance for theories of language evolution. RESEARCH HIGHLIGHTS: Chimpanzees need around 10 years to develop the vocal structural complexity present in the adult repertoire, way beyond the age of emergence of every single vocal unit. Multifaceted ontogenetic processes may drive increases in vocal structural complexity in chimpanzees, particularly increases in social complexity and neuro-muscular maturation. Non-linear increases in vocal complexity coincide with social developmental milestones. Vocal sequences requiring rapid articulatory change emerge later than other vocal sequences, suggesting neuro-muscular maturational processes continue through the juvenile years.

Targeted health and social care interventions for women and infants who are disproportionately impacted by health inequalities in high-income countries: a systematic review.

BACKGROUND: Disadvantaged populations (such as women from minority ethnic groups and those with social complexity) are at an increased risk of poor outcomes and experiences. Inequalities in health outcomes include preterm birth, maternal and perinatal morbidity and mortality, and poor-quality care. The impact of interventions is unclear for this population, in high-income countries (HIC). The review aimed to identify and evaluate the current evidence related to targeted health and social care service interventions in HICs which can improve health inequalities experienced by childbearing women and infants at disproportionate risk of poor outcomes and experiences. METHODS: Twelve databases searched for studies across all HICs, from any methodological design. The search concluded on 8/11/22. The inclusion criteria included interventions that targeted disadvantaged populations which provided a component of clinical care that differed from standard maternity care. RESULTS: Forty six index studies were included. Countries included Australia, Canada, Chile, Hong Kong, UK and USA. A narrative synthesis was undertaken, and results showed three intervention types: midwifery models of care, interdisciplinary care, and community-centred services. These intervention types have been delivered singularly but also in combination of each other demonstrating overlapping features. Overall, results show interventions had positive associations with primary (maternal, perinatal, and infant mortality) and secondary outcomes (experiences and satisfaction, antenatal care coverage, access to care, quality of care, mode of delivery, analgesia use in labour, preterm birth, low birth weight, breastfeeding, family planning, immunisations) however significance and impact vary. Midwifery models of care took an interpersonal and holistic approach as they focused on continuity of carer, home visiting, culturally and linguistically appropriate care and accessibility. Interdisciplinary care took a structural approach, to coordinate care for women requiring multi-agency health and social services. Community-centred services took a place-based approach with interventions that suited the need of its community and their norms. CONCLUSION: Targeted interventions exist in HICs, but these vary according to the context and infrastructure of standard maternity care. Multi-interventional approaches could enhance a targeted approach for at risk populations, in particular combining midwifery models of care with community-centred approaches, to enhance accessibility, earlier engagement, and increased attendance. TRIAL REGISTRATION: PROSPERO Registration number: CRD42020218357.

Heuristics Facilitates the Evolution of Transitive Inference and Social Hierarchy in a Large Group.

Transitive inference (TI) refers to social cognition that facilitates the discernment of unknown relationships between individuals using known relationships. It is extensively reported that TI evolves in animals living in a large group because TI could assess relative rank without deducing all dyadic relationships, which averts costly fights. The relationships in a large group become so complex that social cognition may not be developed adequately to handle such complexity. If members apply TI to all possible members in the group, TI requires extremely highly developed cognitive abilities especially in a large group. Instead of developing cognitive abilities significantly, animals may apply simplified TI we call reference TI in this study as heuristic approaches. The reference TI allows members to recognize and remember social interactions only among a set of reference members rather than all potential members. Our study assumes that information processes in the reference TI comprises (1) the number of reference members based on which individuals infer transitively, (2) the number of reference members shared by the same strategists, and (3) memory capacity. We examined how information processes evolve in a large group using evolutionary simulations in the hawk-dove game. Information processes with almost any numbers of reference members could evolve in a large group as long as the numbers of shared reference member are high because information from the others' experiences is shared. TI dominates immediate inference, which assesses relative rank on direct interactions, because TI could establish social hierarchy more rapidly applying information from others' experiences.

Body size and sexual selection shaped the evolution of parrot calls.

Morphology, habitat and various selective pressures (e.g. social and sexual selection) can influence the evolution of acoustic signals, but the relative importance of their effects is not well understood. The order Psittaciformes (parrots, sensu lato) is a large clade of very vocal and often gregarious species for which large-scale comparative studies of vocalizations are lacking. We measured acoustic traits (duration, sound frequency, frequency bandwidth and sound entropy) of the predominant call type for >200 parrot species to test: (1) for associations with body size; (2) the acoustic adaptation hypothesis (AAH) (predicting differences between forest and open-habitat species); (3) the social complexity hypothesis (predicting more complex calls in gregarious species) and (4) influences of sexual selection (predicting correlated evolution with colour ornamentation). Larger species had on average longer calls, lower sound frequency and wider frequency bandwidth. These associations with body size are all predicted by physical principles of sound production. We found no evidence for the acoustic adaptation and social complexity hypotheses, but perhaps social complexity is associated with vocal traits not studied here, such as call repertoire sizes. More sexually dichromatic species had on average simpler calls (shorter, with lower entropy and narrower frequency bandwidth) indicating an influence of sexual selection, namely an evolutionary negative correlation between colour ornamentation and elaborate acoustic signals, as predicted by the transference hypothesis. Our study is the first large-scale attempt at understanding acoustic diversity across the Psittaciformes, and indicates that body size and sexual selection influenced the evolution of species differences in vocal signals.

Individuality meets plasticity: Endocrine phenotypes across male dominance rank acquisition in guinea pigs living in a complex social environment.

The time of dominance rank acquisition is a crucial phase in male life history that often affects reproductive success and hence fitness. Hormones such as testosterone and glucocorticoids can influence as well as be affected by this process. At the same time, hormone concentrations can show large individual variation. The extent to which such variation is repeatable, particularly in dynamic social settings, is a question of current interest. The aim of the present study was therefore to investigate how dominance rank and individual differences contribute to variance in hormone concentrations during male rank acquisition in a complex social environment. For this purpose, dominance rank as well as baseline testosterone, baseline cortisol, and cortisol responsiveness after exposure to a novel environment were determined in colony-housed guinea pig males from late adolescence through adulthood. Hormone-dominance relationships and repeatability of hormone measures beyond their relation to rank were assessed. There was a significant positive relationship between baseline testosterone and rank, but this link became weaker with increasing age. Baseline cortisol or cortisol responsiveness, in contrast, were not significantly related to dominance. Notably, all three endocrine parameters were significantly repeatable independent of dominance rank from late adolescence through adulthood. Baseline testosterone and cortisol responsiveness showed a significantly higher repeatability than baseline cortisol. This suggests that testosterone titres and cortisol responsiveness represent stable individual attributes even under complex social conditions.

A citizen science approach reveals long-term social network structure in an urban parrot, Cacatua galerita.

Parrots are often referenced in discussions of social and cognitive complexity, yet relatively little is known of their social organization in the wild. In particular, the presence of long-lasting social ties has been highlighted as a hallmark of social complexity; however, the presence of such ties can be masked in fission-fusion systems like that exhibited by most parrot species. Social network analysis has the potential to elucidate such multi-level dynamics. While most parrot species are tropical canopy dwellers, a subset has successfully colonized urban habitats, where they are often the focus of much public interest. Our study takes advantage of this to use citizen science to collect observations of wing-tagged sulphur-crested cockatoos in central Sydney and record their social associations over multiple years. Using a specifically designed mobile phone application 'Wingtags', we collected over >27,000 citizen science reports of wing-tagged cockatoos, and built social networks from spatial-temporal co-occurrences in observations for 130 tagged birds. To validate this novel methodology, we GPS-tagged a subset of wing-tagged birds and compared networks built from both data collection methods. We then examined correlates of social network structure before exploring the temporal dynamics of network structure and social associations. Social networks constructed from GPS data and citizen science data were highly correlated, suggesting that this novel methodology is robust. Network structure exhibited little seasonal variability and was largely driven by roost site choice; however, individuals also showed a surprising degree of mixing between roosts in their foraging associations. Finally, within this larger fission-fusion system, individuals tended to maintain specific social ties for long periods of time. There was an effect of age on these temporal dynamics, with aging individuals increasing both social stability and longevity of associations. Our findings highlight the utility of citizen science to measure social networks in urban species, and add to the evidence that long-lasting social associations can persist in fission-fusion social systems such as those observed in wild sulphur-crested cockatoos.

Community through Culture: From Insects to Whales: How Social Learning and Culture Manifest across Diverse Animal Communities.

It has become increasingly clear that social learning and culture occur much more broadly, and in a wider variety of animal communities, than initially believed. Recent research has expanded the list to include insects, fishes, elephants, and cetaceans. Such diversity allows scientists to expand the scope of potential research questions, which can help form a more complete understanding of animal culture than any single species can provide on its own. It is crucial to understand how culture and social learning present in different communities, as well as what influences community structure and culture may have on one another, so that the results across these different studies may most effectively inform one another. This review presents an overview of social learning in species across a spectrum of community structures, providing the necessary infrastructure to allow a comparison of studies that will help move the field of animal culture forward.

The Complexity of Social Complexity: A Quantitative Multidimensional Approach for Studies of Social Organization.

AbstractThe rapid increase in "big data" during the postgenomic era makes it crucial to appropriately measure the level of social complexity in comparative studies. We argue that commonly used qualitative classifications lump together species showing a broad range of social complexity and falsely imply that social evolution always progresses along a single linear stepwise trajectory that can be deduced from comparing extant species. To illustrate this point, we compared widely used social complexity measures in "primitively eusocial" bumble bees with "advanced eusocial" stingless bees, honey bees, and attine ants. We find that a single species can have both higher and lower levels of complexity compared with other taxa, depending on the social trait measured. We propose that measuring the complexity of individual social traits switches focus from semantic discussions and offers several directions for progress. First, quantitative social traits can be correlated with molecular, developmental, and physiological processes within and across lineages of social animals. This approach is particularly promising for identifying processes that influence or have been affected by social evolution. Second, key social complexity traits can be combined into multidimensional lineage-specific quantitative indices, enabling fine-scale comparison across species that are currently bundled within the same level of social complexity.

Eusociality influences the strength of negative selection on insect genomes.

While much of the focus of sociobiology concerns identifying genomic changes that influence social behaviour, we know little about the consequences of social behaviour on genome evolution. It has been hypothesized that social evolution can influence the strength of negative selection via two mechanisms. First, division of labour can influence the efficiency of negative selection in a caste-specific manner; indirect negative selection on worker traits is theoretically expected to be weaker than direct selection on queen traits. Second, increasing social complexity is expected to lead to relaxed negative selection because of its influence on effective population size. We tested these two hypotheses by estimating the strength of negative selection in honeybees, bumblebees, paper wasps, fire ants and six other insects that span the range of social complexity. We found no consistent evidence that negative selection was significantly stronger on queen-biased genes relative to worker-biased genes. However, we found strong evidence that increased social complexity reduced the efficiency of negative selection. Our study clearly illustrates how changes in behaviour can influence patterns of genome evolution by modulating the strength of natural selection.

How socio-ecological factors influence the differentiation of social relationships: an integrated conceptual framework.

The extent of differentiation of social relationships within groups is a means to assess social complexity, with greater differentiation indicating greater social complexity. Socio-ecological factors are likely to influence social complexity, but no attempt has been made to explain the differentiation of social relationships using multiple socio-ecological factors. Here, we propose a conceptual framework based on four components underlying multiple socio-ecological factors that influence the differentiation of social relationships: the extent of within-group contest competition to access resources, the extent to which individuals differ in their ability to provide a variety of services, the need for group-level cooperation and the constraints on social interactions. We use the framework to make predictions about the degree of relationship differentiation that can be expected within a group according to the cumulative contribution of multiple socio-ecological factors to each of the four components. The framework has broad applicability, since the four components are likely to be relevant to a wide range of animal taxa and to additional socio-ecological factors not explicitly dealt with here. Hence, the framework can be used as the basis for the development of novel and testable hypotheses about intra- and interspecific differences in relationship differentiation and social complexity.

Group living facilitates the evolution of duets in barbets.

The duets of birds have intrigued biologists for a long time, yet much remains unknown about the evolution of these striking collective displays. This is partly because previous studies on duet evolution have been biased to songbirds and neglected other bird groups. In songbirds, the absence of migration has been found to predict the occurrence of duetting, indirectlysupporting the idea that duet communication is linked with pair bonding. Here, we used phylogenetic comparative analyses in a sedentary clade of non-songbirds, the barbets (Capitonidae), to reveal new correlates of duet evolution. We found (i) that duets evolved several times independently in different barbet lineages and (ii) that duetting evolved in association with group living (i.e. the presence of helpers or non-breeding adults during the breeding period), but not with sexual monochromatism or habitat type. Our findings are consistent with a duet function in mate guarding and dominance against subordinate group members as well as joint territory defence. Altogether, the results highlight the importance of the social environment for the evolution of collective signalling.

Do a few tools necessarily mean a few people? A techno-morphological approach to the question of group size at Gesher Benot Ya'aqov, Israel.

The question of Paleolithic group size has been addressed by scholars in many disciplines applying different methods. In our study we apply a novel analytical approach in an attempt to assess the group size of hominins that occupied the Acheulian site of Gesher Benot Ya'aqov, Israel (GBY). Within this framework, we subjected the handaxe assemblages from several archaeological horizons at the site to a morpho-technological analysis. The analysis combined high-resolution three-dimensional geometric morphometric analysis with typo-technological attribute analysis to assess the inter- and intra-assemblage morpho-technological variability. The analysis was also applied to an experimental handaxe assemblage produced by an expert knapper. The results of the analysis show high morphological homogeneity coupled with high technological variability in each of the archaeological assemblages. This pattern is highly indicative of the work of expert knappers, as is also suggested by the comparison between the archaeological and experimental assemblages. The high density of archaeological remains in some of the GBY occupations and their pristine taphonomic condition provide additional support for the involvement of large groups of hominins, although some horizons are far poorer in archaeological remains and hence do not allow such an interpretation. Nevertheless, the fact that in all assemblages the handaxes show the same techno-morphological pattern indicates that they were all produced by expert knappers. As shown by numerous models and ethnographic data, the presence of experts can be viewed as an indication of large and socially complex societies. Thus, although some of the GBY occupations were not formed by large groups, the smaller groups whose activities are recorded were very likely to be part of larger, socially complex cultural groups. This variability in occupational intensity is interpreted as representing an aggregation-dispersal mechanism, similar to those documented in many hunter-gatherer societies.

Predation risk drives social complexity in cooperative breeders.

Predation risk is a major ecological factor selecting for group living. It is largely ignored, however, as an evolutionary driver of social complexity and cooperative breeding, which is attributed mainly to a combination of habitat saturation and enhanced relatedness levels. Social cichlids neither suffer from habitat saturation, nor are their groups composed primarily of relatives. This demands alternative ecological explanations for the evolution of advanced social organization. To address this question, we compared the ecology of eight populations of Neolamprologus pulcher, a cichlid fish arguably representing the pinnacle of social evolution in poikilothermic vertebrates. Results show that variation in social organization and behavior of these fish is primarily explained by predation risk and related ecological factors. Remarkably, ecology affects group structure more strongly than group size, with predation inversely affecting small and large group members. High predation and shelter limitation leads to groups containing few small but many large members, which is an effect enhanced at low population densities. Apparently, enhanced safety from predators by cooperative defense and shelter construction are the primary benefits of sociality. This finding suggests that predation risk can be fundamental for the transition toward complex social organization, which is generally undervalued.

Brain size predicts problem-solving ability in mammalian carnivores.

Despite considerable interest in the forces shaping the relationship between brain size and cognitive abilities, it remains controversial whether larger-brained animals are, indeed, better problem-solvers. Recently, several comparative studies have revealed correlations between brain size and traits thought to require advanced cognitive abilities, such as innovation, behavioral flexibility, invasion success, and self-control. However, the general assumption that animals with larger brains have superior cognitive abilities has been heavily criticized, primarily because of the lack of experimental support for it. Here, we designed an experiment to inquire whether specific neuroanatomical or socioecological measures predict success at solving a novel technical problem among species in the mammalian order Carnivora. We presented puzzle boxes, baited with food and scaled to accommodate body size, to members of 39 carnivore species from nine families housed in multiple North American zoos. We found that species with larger brains relative to their body mass were more successful at opening the boxes. In a subset of species, we also used virtual brain endocasts to measure volumes of four gross brain regions and show that some of these regions improve model prediction of success at opening the boxes when included with total brain size and body mass. Socioecological variables, including measures of social complexity and manual dexterity, failed to predict success at opening the boxes. Our results, thus, fail to support the social brain hypothesis but provide important empirical support for the relationship between relative brain size and the ability to solve this novel technical problem.

Social complexity and kinship in animal societies.

Studies of eusocial invertebrates regard complex societies as those where there is a clear division of labour and extensive cooperation between breeders and helpers. In contrast, studies of social mammals identify complex societies as those where differentiated social relationships influence access to resources and reproductive opportunities. We show here that, while traits associated with social complexity of the first kind occur in social mammals that live in groups composed of close relatives, traits associated with the complexity of social relationships occur where average kinship between female group members is low. These differences in the form of social complexity appear to be associated with variation in brain size and probably reflect contrasts in the extent of conflicts of interest between group members. Our results emphasise the limitations of any unitary concept of social complexity and show that variation in average kinship between group members has far-reaching consequences for animal societies.

Quantifying uncertainty due to fission-fusion dynamics as a component of social complexity.

Groups of animals (including humans) may show flexible grouping patterns, in which temporary aggregations or subgroups come together and split, changing composition over short temporal scales, (i.e. fission and fusion). A high degree of fission-fusion dynamics may constrain the regulation of social relationships, introducing uncertainty in interactions between group members. Here we use Shannon's entropy to quantify the predictability of subgroup composition for three species known to differ in the way their subgroups come together and split over time: spider monkeys (Ateles geoffroyi), chimpanzees (Pan troglodytes) and geladas (Theropithecus gelada). We formulate a random expectation of entropy that considers subgroup size variation and sample size, against which the observed entropy in subgroup composition can be compared. Using the theory of set partitioning, we also develop a method to estimate the number of subgroups that the group is likely to be divided into, based on the composition and size of single focal subgroups. Our results indicate that Shannon's entropy and the estimated number of subgroups present at a given time provide quantitative metrics of uncertainty in the social environment (within which social relationships must be regulated) for groups with different degrees of fission-fusion dynamics. These metrics also represent an indirect quantification of the cognitive challenges posed by socially dynamic environments. Overall, our novel methodological approach provides new insight for understanding the evolution of social complexity and the mechanisms to cope with the uncertainty that results from fission-fusion dynamics.

A computer simulation to investigate the association between gene-based gifting and pair-bonding in early hominins.

This article describes simulation research based on the Hamiltonian theory of gene-based altruism. It investigates the origin of semipermanent breeding bonds during hominin evolution. The research framework is based on a biologically detailed, ecologically situated, multi-agent microsimulation of emergent sociality. The research question tested is whether semipermanent breeding bonds (an emergent homoplastic social construct) might emerge among primate-like agents as the consequence of a mutation capable of supporting involuntary prosocial behavior. The research protocol compared several, single independent-variable longitudinal studies wherein hundreds of generations of autonomous, initially promiscuous, biologically detailed, hominin-like artificial life software agents were born, allowed to forage, reproduce, and die during experimental intervals lasting several simulated millennia. The temporal setting of the experiment was roughly contemporaneous with, or slightly after the time of, the Pan-Homo split. The simulation investigated what would happen if, within a population, a single gene for prosocial behavior (the independent variable in the experiment) was either switched on or switched-off. The null hypothesis predicted that, if the gene was switched off, then semipermanent breeding bonds (the dependent variable) would nonetheless emerge within the population. The results of the simulation rejected this null hypothesis, by showing that semipermanent breeding bonds would reliably emerge among the experimental populations but not among the control groups. Moreover, it was found that, across all experimental settings having constrained population numbers, the portion of each population having no prosocial trait would die out early, whereas the portion with the prosocial trait would survive. Large control populations had no discernible loss. The results of this research imply that, during the early stages of hominin evolution, there might have been a set of initially gene-based, altruistic excess forage-sharing social traits that contributed to the onset of morphological and additional complex social changes characteristic of this group. This work also demonstrates that modern computational technologies can extend our ability to test 'what if' hypotheses appropriate to the study of early hominin evolution.