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Lee, R. D. (2003). Rethinking the evolutionary theory of aging: transfers, not births, shape senescence in social species. Proc Natl Acad Sci U S A, 100(16), 9637–9642.
Abstract: The classic evolutionary theory of aging explains why mortality rises with age: as individuals grow older, less lifetime fertility remains, so continued survival contributes less to reproductive fitness. However, successful reproduction often involves intergenerational transfers as well as fertility. In the formal theory offered here, age-specific selective pressure on mortality depends on a weighted average of remaining fertility (the classic effect) and remaining intergenerational transfers to be made to others. For species at the optimal quantity-investment tradeoff for offspring, only the transfer effect shapes mortality, explaining postreproductive survival and why juvenile mortality declines with age. It also explains the evolution of lower fertility, longer life, and increased investments in offspring.
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Zhou, W. - X., Sornette, D., Hill, R. A., & Dunbar, R. I. M. (2005). Discrete hierarchical organization of social group sizes. Proc Biol Sci, 272(1561), 439–444.
Abstract: The 'social brain hypothesis' for the evolution of large brains in primates has led to evidence for the coevolution of neocortical size and social group sizes, suggesting that there is a cognitive constraint on group size that depends, in some way, on the volume of neural material available for processing and synthesizing information on social relationships. More recently, work on both human and non-human primates has suggested that social groups are often hierarchically structured. We combine data on human grouping patterns in a comprehensive and systematic study. Using fractal analysis, we identify, with high statistical confidence, a discrete hierarchy of group sizes with a preferred scaling ratio close to three: rather than a single or a continuous spectrum of group sizes, humans spontaneously form groups of preferred sizes organized in a geometrical series approximating 3-5, 9-15, 30-45, etc. Such discrete scale invariance could be related to that identified in signatures of herding behaviour in financial markets and might reflect a hierarchical processing of social nearness by human brains.
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Nocera, J. J., Forbes, G. J., & Giraldeau, L. - A. (2006). Inadvertent social information in breeding site selection of natal dispersing birds. Proc Biol Sci, 273(1584), 349–355.
Abstract: Several species use the number of young produced as public information (PI) to assess breeding site quality. PI is inaccessible for synchronously breeding birds because nests are empty by the time the young can collect this information. We investigate if location cues are the next best source of inadvertent social information (ISI) used by young prospectors during breeding site choice. We experimentally deployed ISI as decoys and song playbacks of breeding males in suitable and sub-optimal habitats during pre- and post-breeding periods, and monitored territory establishment during the subsequent breeding season for a social, bobolink (Dolichonyx oryzivorus), and a more solitary species, Nelson's sharp-tailed sparrow (Ammodramus nelsoni). The sparrows did not respond to treatments, but bobolinks responded strongly to post-breeding location cues, irrespective of habitat quality. The following year, 17/20 sub-optimal plots to which bobolink males were recruited were defended for at least two weeks, indicating that song heard the previous year could exert a “carry-over attraction” effect on conspecifics the following year. Sixteen recruited males were natal dispersers, as expected when animals have little opportunity to directly sample their natal habitat quality. We suggest that differences in breeding synchronicity may induce an equivalent clinal distribution of ISI use.
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Peltzer, K., Mabilu, M. G., Mathoho, S. F., Nekhwevha, A. P., Sikhwivhilu, T., & Sinthumule, T. S. (2006). Trauma history and severity of gambling involvement among horse-race gamblers in a South African gambling setting. Psychol Rep, 99(2), 472–476.
Abstract: The purpose of this study was to ascertain the frequency of gambling involvement and the prevalence of problem gambling among horse race gamblers and to discover whether problem gambling in this sample is associated with a history of trauma. Among a sample of 266 South African horse-race gamblers (94% men and 6% women, Mage 46.8 yr., SD = 13.9, range 18-85 years), 31.2% were classified as probable pathological gamblers and 19.9% with problem gambling. Major weekly gambling activities included racetrack betting (82%), purchase of lottery tickets or scratch tickets (35%), purchase of sports lottery tickets (23%), and using casino type games (18%). Trauma history was significantly associated with gambling severity.
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Danchin, E., Giraldeau, L. - A., Valone, T. J., & Wagner, R. H. (2004). Public information: from nosy neighbors to cultural evolution. Science, 305(5683), 487–491.
Abstract: Psychologists, economists, and advertising moguls have long known that human decision-making is strongly influenced by the behavior of others. A rapidly accumulating body of evidence suggests that the same is true in animals. Individuals can use information arising from cues inadvertently produced by the behavior of other individuals with similar requirements. Many of these cues provide public information about the quality of alternatives. The use of public information is taxonomically widespread and can enhance fitness. Public information can lead to cultural evolution, which we suggest may then affect biological evolution.
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Doligez, B., Danchin, E., & Clobert, J. (2002). Public information and breeding habitat selection in a wild bird population. Science, 297(5584), 1168–1170.
Abstract: According to the “public information” hypothesis, some animal species may monitor the current reproductive success of conspecifics to assess local habitat quality and to choose their own subsequent breeding site. To test this hypothesis experimentally, we manipulated two components of public information, the mean number of offspring raised locally (“quantity”) and their condition (“quality”), in the collared flycatcher Ficedula albicollis. Immigration rate decreased with local offspring quantity but did not depend on local offspring quality, suggesting that immigrants are deprived of information regarding local quality. Conversely, emigration rate increased both when local offspring quantity or quality decreased, suggesting that residents can use both components of public information.
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de Waal, F. B. (1999). The end of nature versus nurture. Sci Am, 281(6), 94–99.
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Moehlman, P. D. (2005). Endangered wild equids. Sci Am, 292(3), 74–81.
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Van Schaik, C. (2006). Why are some animals so smart? Sci Am, 294(4), 64–71.
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Heinrich, B., & Bugnyar, T. (2007). Just how smart are ravens? Sci Am, 296(4), 64–71.
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