The evolutionary origins of primate scleral coloration

Primate gaze following behaviors are of great interest to evolutionary scientists studying social cognition. The ability of an organism to determine a conspecifics likely intentions from their gaze direction may confer an advantage to individuals in a social group. This advantage could be cooperative and/or competitive. Humans are unusual in possessing depigmented sclerae whereas most other extant primates, including the closely related chimpanzee, possess dark scleral pigment. The origins of divergent scleral morphologies are currently unclear, though human white sclerae are often assumed to underlie our hyper-cooperative behaviors. Here, we use phylogenetic generalized least squares (PGLS) analyses with previously generated species-level scores of proactive prosociality, social tolerance (both n=15 primate species), and conspecific lethal aggression (n=108 primate species) to provide the first quantitative, comparative test of three complementary hypotheses. The cooperative eye and self-domestication explanations predict white sclerae to be associated with cooperative, rather than competitive, environments. The gaze camouflage hypothesis predicts that dark scleral pigment functions as gaze direction camouflage in competitive social environments. We show that white sclerae in primates are associated with increased cooperative behaviors whereas dark sclerae are associated with reduced cooperative behaviors and increased intra-specific lethal aggression. Our results lend support to all three hypotheses of scleral evolution, suggesting that primate scleral morphologies evolve in relation to variation in social environment.

Progress and challenges in the Costa Rican penitentiary system on the specific needs of LGBTI persons deprived of liberty

Purpose Despite the restricted interpretation of the principle of equality and non-discrimination made by some members of the prison staff in Costa Rica, most of the authorities and policymakers are committed to the express prohibition of unjust treatments on grounds of gender identity and sexual orientation. Notwithstanding, there is a gap between the normative framework and the reality of the detention facilities in the country. This paper aims to present the progress and challenges in the Costa Rican penitentiary system on the specific needs of LGBTI persons deprived of liberty, from a human rights perspective. Design/methodology/approach This paper is the result of the analysis conducted by United Nations Latin American Institute for the Prevention of Crime and the Treatment of Offenders (ILANUD) from the data collected and systemized during a qualitative study, led by the same institution in 2016, regarding the situation of Lesbian, Gay, Bisexual, Trans and Intersex Persons (LGBTI) persons deprived of liberty. These findings and a review of the actions implemented recently by the competent authorities to protect the rights of these population groups allowed to present an approach of the current situation of the Costa Rican penitentiary system. Findings While acknowledging the gravity of the violations of fundamental rights of LGBTI people in prison, they are far from showing a systematic pattern of aggression or discrimination against those people. What they do indicate is a penitentiary system that reproduces and exacerbates the marginalization and discrimination experienced by these populations in society. Despite the implementation of some measures to meet the particular needs of these groups, there is also evidence of an institutional culture that tolerates and normalizes certain levels of verbal violence and non-lethal aggression perpetrated by some system staff and by other individuals deprived of liberty. Practical implications Visualize the discrimination faced by some of the most invisible prisoners in the penitentiary system. Highlight some of the challenges that might be addressed to protect the rights of certain groups of prisoners affected by structural discrimination provide key data to identify the task list that should be guiding the actions to strengthen human rights guarantees for LGBTI people in prison. Present some good practices implemented by the Costa Rican penitentiary system, which might be useful for some other countries of the region. Originality/value There is a lack of information in Latin America about the rights situation of people that, besides the imprisonment, faced some other conditions of vulnerability, such as gender identity or sexual orientation. In a region where overpopulation, precarious living conditions and the critical situation of the prisons are no longer news, this paper pretends to draw attention to the progress and challenges of the penitentiary system concerning some of the most marginalized people in prison. In that regard, this document constitutes also a way of vindication of their rights.

Resource scarcity drives lethal aggression among prehistoric hunter-gatherers in central California

The origin of human violence and warfare is controversial, and some scholars contend that intergroup conflict was rare until the emergence of sedentary foraging and complex sociopolitical organization, whereas others assert that violence was common and of considerable antiquity among small-scale societies. Here we consider two alternative explanations for the evolution of human violence: (i) individuals resort to violence when benefits outweigh potential costs, which is likely in resource poor environments, or (ii) participation in violence increases when there is coercion from leaders in complex societies leading to group level benefits. To test these hypotheses, we evaluate the relative importance of resource scarcity vs. sociopolitical complexity by evaluating spatial variation in three macro datasets from central California: (i) an extensive bioarchaeological record dating from 1,530 to 230 cal BP recording rates of blunt and sharp force skeletal trauma on thousands of burials, (ii) quantitative scores of sociopolitical complexity recorded ethnographically, and (iii) mean net primary productivity (NPP) from a remotely sensed global dataset. Results reveal that sharp force trauma, the most common form of violence in the record, is better predicted by resource scarcity than relative sociopolitical complexity. Blunt force cranial trauma shows no correlation with NPP or political complexity and may reflect a different form of close contact violence. This study provides no support for the position that violence originated with the development of more complex hunter-gatherer adaptations in the fairly recent past. Instead, findings show that individuals are prone to violence in times and places of resource scarcity.

Female infanticide and female-directed lethal targeted aggression in a group of ring-tailed lemurs (Lemur catta)

We report on extremely rare events of lethal aggression in a semi-captive group of ring-tailed lemurs (Lemur catta) during the birth season 2014. This aggression was targeted against the two highest-ranking females. It led to their eviction from the group and following a final aggressive interaction four days later to their deaths caused by almost all the females and probably even two males of their former group. These events of targeted aggression erupted initially following an infanticide by the highest-ranking female directed at the offspring of a subordinate. Even for ring-tailed lemurs this is a very special case of changeover of power between two different matrilines in a group. In accordance with other studies we suggest that these events of targeted aggression were based on the growing group size and were acts of female reproductive competition during birth season. With the intensity of the events we add new aspects to the existing knowledge of aggressive interactions in ring-tailed lemurs.

Making sense of economic deprivation as a predictor of suicide and homicide: A nationwide register-study

IntroductionClassical work on lethal aggression often viewed suicide and homicide as sharing a common source.ObjectiveThe present investigation explores the association between measures of social deprivation on the relative incidence of suicide over homicide in Italian provinces.MethodsData refer to official government sources on lethal violence rates and measures of social deprivation. The central dependent variable is termed SHR or the suicide rate expressed as a proportion of the sum of the suicide and homicide rates Data were available for the 103 Italian provinces.ResultsThe SHR had three significant predictors. The greater the percentage of the population with low education, the lesser the tendency towards suicide. The tendency towards suicide was also predicted by rental housing, the greater the percentage of the population living in rental housing the less the tendency towards suicide. The inverse of the unemployment rate also predicted the SHR. Given that the measure follows an inverse function, the greater the unemployment rate the lesser the tendency towards suicide relative to homicide (SHR). We can interpret the results relative to a homicidal tendency in the SHR: the greater the low education percentage of the population, the greater the homicidal tendency, and the greater the rental housing percentage, the greater the homicidal tendency in the SHR.ConclusionThe results are consistent with a stream of previous research that connects deprivation with a relatively high probability for disadvantaged populations to direct aggression outwardly in the form of homicide rather than inwardly in the form of suicide.Disclosure of interestThe authors have not supplied their declaration of competing interest.

Myths about hunter-gatherers redux: nomadic forager war and peace

Purpose – The purpose of this paper is to critique several studies that claim to show that nomadic foragers engage in high levels of inter-group aggression. This is done through exploring four myths: nomadic foragers are warlike; there was a high rate of war mortality in the Pleistocene; the nomadic forager data support the “chimpanzee model” of lethal raiding psychology; and contact and state influence inevitably decrease aggression in nomadic forager societies. Design/methodology/approach – Using exact criteria, a sample of 21 nomadic forager societies is derived from the Standard Cross-Cultural Sample. This sampling method minimizes the chance of sampling bias, a shortcoming that has plagued previous studies. Only the highest quality ethnographic data, those classified as Primary Authority Sources, are used, which results in data on 148 cases of lethal aggression. The specifics of the lethal aggression cases are then discussed vis-à-vis the four myths to demonstrate the disjuncture between the data and the myths. Findings – All four myths are found to be out of step with actual data on nomadic forager war and peace. Overall, the default interaction pattern of nomadic foragers is to get along with neighbors rather than make war against them. The findings contradict both assertions that there was a high level of war mortality among nomadic foragers of the Pleistocene and the chimpanzee model's proposal that human males have a tendency or predisposition to form coalitions and make lethal attacks on members of neighboring groups. Research limitations/implications – Consideration of nomadic forager war and peace should be contextualized in terms of social organization, contact history (including ethnocide, displacement, and other factors), and the current situation faced by extant forager populations. As in other contexts, the introduction of alcohol at contact or subsequently has increased nomadic forager aggression. Practical implications – Propositions as to the aggressiveness of nomadic foragers should be viewed with skepticism because they are contradicted by data and a contextual view of nomadic forager social organization and ethnohistory. Social implications – The debate over nomadic forager war and peace is connected to larger debates in modern society about the nature of human nature and has real-world implications regarding foreign policy and political approaches toward war and peace. Originality/value – A critique of sampling, methodology, and theory is provided in this area.