scholarly journals Are elder siblings helpers or competitors? Antagonistic fitness effects of sibling interactions in humans

2013 ◽  
Vol 280 (1750) ◽  
pp. 20122313 ◽  
Author(s):  
Aïda Nitsch ◽  
Charlotte Faurie ◽  
Virpi Lummaa
Keyword(s):  
Life History ◽  
Sexual Maturity ◽  
Life History Stage ◽  
Same Sex ◽  
Fitness Effects ◽  
Sibling Interactions ◽  
Fitness Consequences ◽  
Opposite Sex ◽  
Fitness Measures

Determining the fitness consequences of sibling interactions is pivotal for understanding the evolution of family living, but studies investigating them across lifetime are lacking. We used a large demographic dataset on preindustrial humans from Finland to study the effect of elder siblings on key life-history traits. The presence of elder siblings improved the chances of younger siblings surviving to sexual maturity, suggesting that despite a competition for parental resources, they may help rearing their younger siblings. After reaching sexual maturity however, same-sex elder siblings' presence was associated with reduced reproductive success in the focal individual, indicating the existence of competition among same-sex siblings. Overall, lifetime fitness was reduced by same-sex elder siblings' presence and increased by opposite-sex elder siblings' presence. Our study shows opposite effects of sibling interactions depending on the life-history stage, and highlights the need for using long-term fitness measures to understand the selection pressures acting on sibling interactions.

Juvenile social dynamics reflect adult reproductive strategies in bottlenose dolphins

2020 ◽  
Vol 31 (5) ◽  
pp. 1159-1171
Author(s):  
Allison A Galezo ◽  
Vivienne Foroughirad ◽  
Ewa Krzyszczyk ◽  
Céline H Frère ◽  
Janet Mann
Keyword(s):  
Reproductive Strategies ◽  
Sexual Maturity ◽  
Social Dynamics ◽  
Bottlenose Dolphins ◽  
Life History Stage ◽  
Affiliative Behavior ◽  
Same Sex ◽  
Juvenile Period ◽  
Social Associations ◽  
Maternal Protection

Abstract The juvenile period is a challenging life-history stage, especially in species with a high degree of fission–fusion dynamics, such as bottlenose dolphins, where maternal protection is virtually absent. Here, we examined how juvenile male and female bottlenose dolphins navigate this vulnerable period. Specifically, we examined their grouping patterns, activity budget, network dynamics, and social associations in the absence of adults. We found that juveniles live in highly dynamic groups, with group composition changing every 10 min on average. Groups were generally segregated by sex, and segregation was driven by same-sex preference rather than opposite-sex avoidance. Juveniles formed strong associations with select individuals, especially kin and same-sex partners, and both sexes formed cliques with their preferred partners. Sex-specific strategies in the juvenile period reflected adult reproductive strategies, in which the exploration of potential social partners may be more important for males (which form long-term alliances in adulthood) than females (which preferentially associate with kin in adulthood). Females spent more time alone and were more focused on foraging than males, but still formed close same-sex associations, especially with kin. Males cast a wider social net than females, with strong same-sex associations and many male associates. Males engaged in more affiliative behavior than females. These results are consistent with the social bonds and skills hypothesis and suggest that delayed sexual maturity in species with relational social complexity may allow individuals to assess potential associates and explore a complex social landscape without the risks associated with sexual maturity (e.g., adult reproductive competition; inbreeding).

scholarly journals INTESTATE SUCCESSION AND THE SURVIVOR OF AN UNFORMALISED SAME-SEX CONJUGAL RELATIONSHIP: Laubscher No v Duplan 2017 (2) SA 264 (CC)

Obiter ◽  
2018 ◽  
Vol 39 (1) ◽  
Author(s):  
Michael Cameron Wood-Bodley
Keyword(s):  
Constitutional Court ◽  
Same Sex ◽  
Same Sex Couples ◽  
Lesbian Relationship ◽  
Substantive Equality ◽  
Civil Union ◽  
Opposite Sex ◽  
Domestic Partnerships ◽  
The Right

When a person dies intestate his or her heirs are determined by the provisions of section 1(1) and (2) of the Intestate Succession Act 81 of 1987. Included amongst the heirs is the deceased’s surviving spouse, who either takes the entire estate or shares it with the deceased’s descendants (if any). Historically, the reference to “spouse” in the Act was taken to mean a person to whom the deceased was married in terms of the Marriage Act 25 of 1961. Accordingly, persons who were married to the deceased merely by religious rites and persons with whom the deceased was in a long-term conjugal relationship that was unformalised by marriage were excluded.The advent of constitutional democracy in South Africa resulted in a number of challenges to this status quo through reliance on the equality clause of the Bill of Rights. As a result of these challenges it has now been recognised that the survivor of a Hindu marriage, a monogamous Muslim marriage, and a polygynous Muslim marriage all have the right to inherit on intestacy as a “spouse”. Furthermore, in a groundbreaking decision in Gory v Kolver NO (Starke and others intervening) (2007 (4) SA 97 (CC)) the Constitutional Court recognised that the exclusion of the surviving partner of a gay or lesbian relationship from the right to inherit on intestacy was unconstitutional, and directed that the relevant sections of the Intestate Succession Act be amended by a reading-in of additional words to remedy the unconstitutionality. These words conferred the right to inherit on intestacy on the survivor of a monogamous permanent same-sex partnership in which the partners undertook reciprocal duties of support. At the time of writing no survivor of an unformalised opposite-sex relationship has challenged his or her exclusion from intestate succession. Possibly this reticence has been influenced by the decision in Volks NO v Robinson (2005 (5) BCLR 446 (CC)) (hereinafter “Volks”). In Volks the Constitutional Court held that it is not unconstitutional for the Maintenance of Surviving Spouses Act 27 of 1990 to distinguish between married and unmarried persons by giving the survivor of a marriage a claim for reasonable maintenance against the estate of the deceased spouse but not giving a similar claim to the survivor of a relationship in which the parties did not marry.Paleker has raised the question whether the Gory order “must still be applied in light of the Civil Union Act” but he comes to no firm conclusion, and states tentatively that “if marriage … is a precondition for inheriting, persons in same-sex unions who have not solemnised their relationship after the coming into force of the Civil Union Act … may be precluded from inheriting intestate from each other”. On the other hand De Waal and Schoeman-Malan are clearly of the view that the order in the Gory case still operates and – whilst regarding the current position as “anomalous” – they state that it “will probably continue until the Domestic Partnerships Bill [GN36 in GG 30663 of 2008-1-14] eventually does become law”. This has also been the interpretation accepted by the Master’s office acting on advice from the Senior State Law Advisor. The different treatment accorded same-sex couples by the continued retention of the benefits conferred by Gory has been defended on the grounds of substantive equality, since many practical obstacles still stand in the way of same-sex couples formalising their relationships.The question of the continued applicability of the reading-in order in Gory has now come before the Constitutional Court in Laubscher NO v Duplan (2017 (2) SA 264 (CC)) and it is this case which is the focus of this note.

scholarly journals The Manifestations and Characteristics of School Bullying in China: An Analysis Based on 50 Typical Cases Reported on the Internet

2021 ◽  
Vol 5 (4) ◽  
pp. 36
Author(s):  
Ruohan Li ◽  
Na Gao
Keyword(s):  
Daily Life ◽  
School Bullying ◽  
The Internet ◽  
Same Sex ◽  
Opposite Sex ◽  
Long Term Behavior ◽  
Physical Bullying ◽  
Girl Students

This is a case study of school bullying in China. There are two main types of school bullying: mental bullying and physical bullying which is the main form of school bullying in China. It is worth noting that the frequency of sexual bullying and derivative behaviors of school bullying are in increasing now. School bullying is often a repetitive and long-term behavior and often committed by multiple people. The study shows that high school is the main place of school bullying in China and the frictions of daily life is the main cause of school bullying. The study also shows that, compared with the opposite sex, bullying behaviors between the same sex occur more frequently, and girl students are more likely to be the victims of school bullying.

The Evolution of Same-Sex Attraction in Women

2019 ◽  
Vol 40 (2) ◽  
pp. 104-110 ◽  
Author(s):  
Menelaos Apostolou
Keyword(s):  
Strong Support ◽  
Considerable Proportion ◽  
Heterosexual Men ◽  
High Tolerance ◽  
Same Sex ◽  
Short Term ◽  
Men And Women ◽  
Sex Attraction ◽  
Opposite Sex

Abstract. A considerable proportion of the population experiences varying degrees of same-sex attraction. It has been proposed that men exhibit high tolerance to their partner’s same-sex infidelity, which allows such predispositions to exist in a relative high frequency in the population. On this basis, the hypothesis was tested that heterosexual men and women would differ in their tolerance level, with men exhibiting higher tolerance to same-sex infidelity than women. Evidence from an online sample of 590 heterosexual Greek-speaking participants provided strong support for this hypothesis. In particular, the vast majority of women exhibited low tolerance, while about one in two men exhibited high tolerance to same-sex infidelity. Furthermore, men and women exhibited higher tolerance to the same-sex infidelity of their long-term than of their short-term partners, with men exhibiting higher tolerance in the latter case. In addition, women exhibited low tolerance to opposite-sex and same-sex infidelity, but men exhibited low tolerance to opposite-sex infidelity, but much higher tolerance to same-sex infidelity.

scholarly journals Cross-cousin marriage among the Yanomamö shows evidence of parent–offspring conflict and mate competition between brothers

2017 ◽  
Vol 114 (13) ◽  
pp. E2590-E2607 ◽  
Author(s):  
Napoleon A. Chagnon ◽  
Robert F. Lynch ◽  
Mary K. Shenk ◽  
Raymond Hames ◽  
Mark V. Flinn
Keyword(s):  
Parental Control ◽  
Mating Strategies ◽  
Cultural Norms ◽  
Mate Competition ◽  
Same Sex ◽  
Cousin Marriage ◽  
Fitness Consequences ◽  
Traditional Societies ◽  
Opposite Sex ◽  
Lower Fertility

Marriage in many traditional societies often concerns the institutionalized exchange of reproductive partners among groups of kin. Such exchanges most often involve cross-cousins—marriage with the child of a parent’s opposite-sex sibling—but it is unclear who benefits from these exchanges. Here we analyze the fitness consequences of marrying relatives among the Yanomamö from the Amazon. When individuals marry close kin, we find that (i) both husbands and wives have slightly lower fertility; (ii) offspring suffer from inbreeding depression; (iii) parents have more grandchildren; and (iv) siblings, especially brothers, benefit when their opposite-sex siblings marry relatives but not when their same-sex siblings do. Therefore, individuals seem to benefit when their children or opposite-sex siblings marry relatives but suffer costs when they, their parents, or same-sex siblings do. These asymmetric fitness outcomes suggest conflicts between parents and offspring and among siblings over optimal mating strategies. Parental control of marriages is reinforced by cultural norms prescribing cross-cousin marriage. We posit that local mate competition combined with parental control over marriages may escalate conflict between same-sex siblings who compete over mates, while simultaneously forging alliances between opposite-sex siblings. If these relationships are carried forward to subsequent generations, they may drive bilateral cross-cousin marriage rules. This study provides insights into the evolutionary importance of how kinship and reciprocity underlie conflicts over who controls mate choice and the origins of cross-cousin marriage prescriptions.

scholarly journals Male Tolerance to Same-Sex Infidelity: A Cross-Cultural Investigation

2019 ◽  
Vol 17 (2) ◽  
pp. 147470491984389
Author(s):  
Yan Wang ◽  
Menelaos Apostolou
Keyword(s):  
Cross Cultural ◽  
Heterosexual Men ◽  
Same Sex ◽  
Short Term ◽  
Men And Women ◽  
Cultural Contexts ◽  
Sex Attraction ◽  
Female Partners ◽  
Opposite Sex

There is accumulating evidence that heterosexual men exhibit tolerance to their partners’ same-sex infidelity. The current study examined such tolerance in the Chinese ( N = 949) and the British ( N = 305) cultural contexts. Consistent with the predictions derived from an evolutionary framework, across different cultural settings, men exhibited higher tolerance than women to their partners’ same-sex infidelity. In addition, if they had to choose, men were considerably more likely than women to prefer their partners to cheat with an individual of the same than of the opposite sex. Participants were also more tolerant of infidelity involving their short-term than their long-term partners. Moreover, men who preferred same-sex attraction in women were more tolerant to the same-sex infidelity of their female partners than men who did not share these preferences. Finally, men and women who experienced same-sex attractions indicated higher tolerance to infidelity. The implications of these finding for the evolution of same-sex attraction in women were further discussed.

Multiple mating is linked to social setting and benefits the males in a communally rearing mammal

2019 ◽  
Vol 30 (3) ◽  
pp. 675-687 ◽  
Author(s):  
Luis A Ebensperger ◽  
Loreto A Correa ◽  
Álvaro Ly Prieto ◽  
Felipe Pérez de Arce ◽  
Sebastian Abades ◽  
...  
Keyword(s):  
Multiple Mating ◽  
Social Groups ◽  
Group Living ◽  
Spatial Relations ◽  
Social Setting ◽  
Female Reproductive Success ◽  
Fitness Effects ◽  
Social Species ◽  
Fitness Consequences ◽  
Opposite Sex

Abstract Individuals in social species may mate with multiple opposite-sex individuals, including members of the same or different social groups. This variation may be linked to genetic benefits, where multiple mating decreases risk of inbreeding. Multiple mating may also be constrained by the sociospatial setting through its effect on availability of mates. Because multiple mating with individuals from same or different groups may determine sex-specific fitness effects, we also examined how multiple mating modulates social benefits of females and males. We used 7 years of data on demography, social organization, and genetics of a natural population of the group-living and colonial rodent, Octodon degus, to determine how kin and sex composition within social groups, and spatial relations between these groups (i.e., colonial habits) influence multiple mating and its fitness consequences. Males (81.3%) and females (64.9%) produced offspring with multiple opposite-sex individuals within groups and with individuals of neighboring groups. Thus, polygynandry was the dominant mating system in the degu population examined. Multiple mating in degus was high when compared with estimates reported in other social mammals. Variation in female and male multiple mating was better explained by social setting through its effect on availability of potential mates rather than by benefits derived from decreasing risk of inbreeding. Finally, our study revealed how multiple mating enhances male, but not female reproductive success.

scholarly journals Long-term repeatability in social behaviour suggests stable social phenotypes in wild chimpanzees

2020 ◽  
Vol 7 (8) ◽  
pp. 200454 ◽  
Author(s):  
Patrick J. Tkaczynski ◽  
Alexander Mielke ◽  
Liran Samuni ◽  
Anna Preis ◽  
Roman M. Wittig ◽  
...  
Keyword(s):  
Life History ◽  
Individual Differences ◽  
Social Behaviour ◽  
Group Living ◽  
Ecological Factors ◽  
Life History Stage ◽  
Dominance Hierarchies ◽  
Decision Making Processes ◽  
Fitness Benefits

Consistent individual differences in social phenotypes have been observed in many animal species. Changes in demographics, dominance hierarchies or ecological factors, such as food availability or disease prevalence, are expected to influence decision-making processes regarding social interactions. Therefore, it should be expected that individuals show flexibility rather than stability in social behaviour over time to maximize the fitness benefits of social living. Understanding the processes that create and maintain social phenotypes requires data encompassing a range of socioecological settings and variation in intrinsic state or life-history stage or strategy. Using observational data spanning up to 19 years for some individuals, we demonstrate that multiple types of social behaviour are repeatable over the long term in wild chimpanzees, a long-lived species with complex fission–fusion societies. We controlled for temporal, ecological and demographic changes, limiting pseudo-repeatability. We conclude that chimpanzees living in natural ecological settings have relatively stable long-term social phenotypes over years that may be independent of life-history or reproductive strategies. Our results add to the growing body of the literature suggesting consistent individual differences in social tendencies are more likely the rule rather than the exception in group-living animals.

Life-history characteristics of the yakka skink, Egernia rugosa, indicate long-term social structure

2016 ◽  
Vol 64 (5) ◽  
pp. 335 ◽  
Author(s):  
Stephen Peck ◽  
Michael G. Gardner ◽  
Jennifer M. Seddon ◽  
Greg Baxter
Keyword(s):  
Life History ◽  
Life Expectancy ◽  
Genetic Analysis ◽  
Social Structure ◽  
Litter Size ◽  
Sexual Maturity ◽  
Age Cohorts ◽  
South West ◽  
Life History Characteristics

One lineage of squamates, the Egernia group, has received particular study due to stable aggregations identified in many of the species. Egernia rugosa is a large, terrestrial, viviparous skink and has been reported living communally. To investigate whether this species lives in social aggregations, we examined life-history characteristics in one population within the Mulga Lands bioregion of south-west Queensland. We found this skink used both active and inactive rabbit burrows. Parturition occurred in January/February and took several days to complete, with a mean litter size of 2.4 and a mean snout–vent length (SVL) of 84.5 mm. Six subadult age cohorts were identified. Juveniles took at least five years to reach sexual maturity and lizards had a life expectancy of >12 years. Lizards were found clustered in aggregations of up to 21 individuals (mean = 7.21) of multiple ages. An average of 50% (range = 31–67%) of all individuals within each of the age cohorts were located at their original location for two or more seasons. Dispersal was recorded for older subadult lizards. These characteristics support the hypothesis that E. rugosa aggregations comprise long-term family units; however, genetic analysis would be needed to confirm kin-based associations.

Relationships between temperature and Pacific hake distribution vary across latitude and life-history stage

2020 ◽  
Vol 639 ◽  
pp. 185-197 ◽  
Author(s):  
MJ Malick ◽  
ME Hunsicker ◽  
MA Haltuch ◽  
SL Parker-Stetter ◽  
AM Berger ◽  
...  
Keyword(s):  
Life History ◽  
Environmental Effects ◽  
Environmental Conditions ◽  
Vancouver Island ◽  
Additive Models ◽  
Life History Stage ◽  
Fish Stocks ◽  
Merluccius Productus ◽  
Multiple Dimensions ◽  
Effects Of Temperature

Environmental conditions can have spatially complex effects on the dynamics of marine fish stocks that change across life-history stages. Yet the potential for non-stationary environmental effects across multiple dimensions, e.g. space and ontogeny, are rarely considered. In this study, we examined the evidence for spatial and ontogenetic non-stationary temperature effects on Pacific hake Merluccius productus biomass along the west coast of North America. Specifically, we used Bayesian additive models to estimate the effects of temperature on Pacific hake biomass distribution and whether the effects change across space or life-history stage. We found latitudinal differences in the effects of temperature on mature Pacific hake distribution (i.e. age 3 and older); warmer than average subsurface temperatures were associated with higher biomass north of Vancouver Island, but lower biomass offshore of Washington and southern Vancouver Island. In contrast, immature Pacific hake distribution (i.e. age 2) was better explained by a nonlinear temperature effect; cooler than average temperatures were associated with higher biomass coastwide. Together, our results suggest that Pacific hake distribution is driven by interactions between age composition and environmental conditions and highlight the importance of accounting for varying environmental effects across multiple dimensions.

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