Kin Selection in Primate Groups

Altruism poses a problem for evolutionary biologists because natural selection is not expected to favor behaviors that are beneficial to recipients, but costly to actors. The theory of kin selection, first articulated by Hamilton (1964), provides a solution to the problem. Hamilton's well-known rule (br > c) provides a simple algorithm for the evolution of altruism via kin selection. Because kin recognition is a crucial requirement of kin selection, it is important to know whether and how primates can recognize their relatives. While conventional wisdom has been that primates can recognize maternal kin, but not paternal kin, this view is being challenged by new findings. The ability to recognize kin implies that kin selection may shape altruistic behavior in primate groups. I focus on two cases in which kin selection is tightly woven into the fabric of social life. For female baboons, macaques, and vervets maternal kinship is an important axis of social networks, coalitionary activity, and dominance relationships. Detailed studies of the patterning of altruistic interactions within these species illustrate the extent and limits of nepotism in their social lives. Carefully integrated analyses of behavior, demography, and genetics among red howlers provide an independent example of how kin selection shapes social organization and behavior. In red howlers, kin bonds shape the life histories and reproductive performance of both males and female. The two cases demonstrate that kin selection can be a powerful source of altruistic activity within primate groups. However, to fully assess the role of kin selection in primate groups, we need more information about the effects of kinship on the patterning of behavior across the Primates and accurate information about paternal kin relationships.     

Leadership in Moving Human Groups

How is movement of individuals coordinated as a group? This is a fundamental question of social behaviour, encompassing phenomena such as bird flocking, fish schooling, and the innumerable activities in human groups that require people to synchronise their actions. We have developed an experimental paradigm, the HoneyComb computer-based multi-client game, to empirically investigate human movement coordination and leadership. Using economic games as a model, we set monetary incentives to motivate players on a virtual playfield to reach goals via players'' movements. We asked whether (I) humans coordinate their movements when information is limited to an individual group member''s observation of adjacent group member motion, (II) whether an informed group minority can lead an uninformed group majority to the minority''s goal, and if so, (III) how this minority exerts its influence. We showed that in a human group – on the basis of movement alone – a minority can successfully lead a majority. Minorities lead successfully when (a) their members choose similar initial steps towards their goal field and (b) they are among the first in the whole group to make a move. Using our approach, we empirically demonstrate that the rules of swarming behaviour apply to humans. Even complex human behaviour, such as leadership and directed group movement, follow simple rules that are based on visual perception of local movement.     

Selection in Reference to Biological Groups. V. Analysis of Full-Sib Groups

Previous studies in this series have dealt with the consequences of truncation selection operating with respect to random groups within which geno-full-sib group structure. The objective is to compare the results of individual and group selection as these methods operate on populations of random versus typic interaction may exist. The present study deal with a non-random, full-sib groups. In almost all comparisons individual selection is found to be qualitatively and quantitatively superior when used in conjunction with full-sib groups. This is due to the fact that the change in gene frequency for full-sib groups is a function of both direct and associate effects, whereas with random groups it is a function of direct effects only. With regard to group selection the efficiency is invariably superior when selection operates on non-random, full-sib rather than random groups.     

Deciphering Interactions in Moving Animal Groups

Collective motion phenomena in large groups of social organisms have long fascinated the observer, especially in cases, such as bird flocks or fish schools, where large-scale highly coordinated actions emerge in the absence of obvious leaders. However, the mechanisms involved in this self-organized behavior are still poorly understood, because the individual-level interactions underlying them remain elusive. Here, we demonstrate the power of a bottom-up methodology to build models for animal group motion from data gathered at the individual scale. Using video tracks of fish shoal in a tank, we show how a careful, incremental analysis at the local scale allows for the determination of the stimulus/response function governing an individual''s moving decisions. We find in particular that both positional and orientational effects are present, act upon the fish turning speed, and depend on the swimming speed, yielding a novel schooling model whose parameters are all estimated from data. Our approach also leads to identify a density-dependent effect that results in a behavioral change for the largest groups considered. This suggests that, in confined environment, the behavioral state of fish and their reaction patterns change with group size. We debate the applicability, beyond the particular case studied here, of this novel framework for deciphering interactions in moving animal groups.     

Free Sulfhydryl Groups in Ripening Fruits

Ripening was found to be accompanied by an increase in sulfhydryl (SH) group content in several fruits. In ripening, climacteric,tomato fruits, this increase was due mostly to an increase inthe glutathione level. In orange, a non-climacteric fruit, therelatively high SH levels did not change during developmentand maturation. Non-ripening tomato mutants, e.g., rin and nor,were characterized by low and constant SH levels during fruitgrowth and senescence. Ripening-inducing storage conditions,such as high temperature (30?C) and ethylene treatment, concomitantlyhastened the increase in SH level in fast-ripening tomato varieties.Storage conditions that slowed down the ripening process, suchas low temperatures (2, 12?C) and low oxygen levels (5%), sloweddown the increase in SH content. Storage of red tomatoes at30?C caused an increase in the SH content in comparison withlower temperature treatments (2, 12, 20?C). SH compounds (reducedglutathione, cysteine), dithiothreitol and an SH-binding compound(n-ethylmaleimide), did not affect the ripening process of greentomatoes. The results suggest that the increase in SH groupsaccompanies the ripening processes rather than regulating them. (Received April 26, 1982; Accepted September 6, 1982)     

The Binding Groups in Ovomucin-lysozyme Interaction

The ovomucin-lysozyme aggregation was remarkably affected by pH or ionic strength. The extent of interaction of F-ovomucin with lysozyme was much larger than that of S-ovomucin. The ovomucin-lysozyme interaction decreased correspondingly, at a rate depending on the time at which ovomucin was modified by neuraminidase. On the other hand, the ovomucin-lysozyme interaction disappeared completely by acetylation, succinilation, or carbamylation of lysyl ε-amino groups in lysozyme, but it was not greatly affected by guanidination of lysyl ε-amino groups in lysozyme. From these results, it was confirmed that the electrostatic interaction between the negative charges of the terminal sialic acid in ovomucin and the positive charges of lysyl ε-amino groups in lysozyme is essential for the ovomucin-lysozyme interaction.     

Paternity Recognition in Multi-male Primate Groups

A traditional view of multi-male primate groups has held thatmales provide relatively little direct care to infants, possiblyas a result of low confidence of paternity associated with arelatively promiscuous breeding system. In the last five yearsthis view has changed as a result of a careful documentationof intimate male-infant affiliations in certain species, especiallythe savanna-dwelling baboons (Papio spp.). The occurrence ofthese affiliations raises the question as to whether males carefor their own offspring preferentially and, if so, on what basismale confidence of paternity is mediated. Recent field studiesof baboons suggest that male-infant relationships are mediatedthrough affiliations between the males and the infants' mothers,but the degree to which these male-female affiliations are basedon prior mating experience (hence, paternity) has not been established. Comparative studies of male-infant relations in primates havegiven little attention to the variation in the intensity andform of male care patterns within the set of species that havea multi-male social organization. Among multi-male species,male care of young is reported most often in baboons and barbarymacaques (Macaca sylvanus) and least often in other macaques,chimpanzees (Pan troglodytes), and vervet monkeys (Cercopithecus).This interspecific variation may result both from differencesin the importance of male care to infant survival and from differencesin male confidence of paternity, which in turn may relate toseasonal breeding patterns and, in particular, to the presenceor absence of conspicuous signs of ovulation in females.