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Warneken, F., & Tomasello, M. (2009). Varieties of altruism in children and chimpanzees. In Trends in cognitive sciences (Vol. 13, pp. 397–402). Elsevier Science,.
Abstract: Recent empirical research has shed new light on the perennial question of human altruism. A number of recent studies suggest that from very early in ontogeny young children have a biological predisposition to help others achieve their goals, to share resources with others and to inform others of things helpfully. Humans nearest primate relatives, such as chimpanzees, engage in some but not all of these behaviors: they help others instrumentally, but they are not so inclined to share resources altruistically and they do not inform others of things helpfully. The evolutionary roots of human altruism thus appear to be much more complex than previously supposed.
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Warmuth, V., Eriksson, A., Bower, M. A., Barker, G., Barrett, E., Hanks, B. K., et al. (2012). Reconstructing the origin and spread of horse domestication in the Eurasian steppe. Proc Natl Acad Sci U S A, .
Abstract: Despite decades of research across multiple disciplines, the early history of horse domestication remains poorly understood. On the basis of current evidence from archaeology, mitochondrial DNA, and Y-chromosomal sequencing, a number of different domestication scenarios have been proposed, ranging from the spread of domestic horses out of a restricted primary area of domestication to the domestication of numerous distinct wild horse populations. In this paper, we reconstruct both the population genetic structure of the extinct wild progenitor of domestic horses, Equus ferus, and the origin and spread of horse domestication in the Eurasian steppes by fitting a spatially explicit stepping-stone model to genotype data from >300 horses sampled across northern Eurasia. We find strong evidence for an expansion of E. ferus out of eastern Eurasia about 160 kya, likely reflecting the colonization of Eurasia by this species. Our best-fitting scenario further suggests that horse domestication originated in the western part of the Eurasian steppe and that domestic herds were repeatedly restocked with local wild horses as they spread out of this area. By showing that horse domestication was initiated in the western Eurasian steppe and that the spread of domestic herds across Eurasia involved extensive introgression from the wild, the scenario of horse domestication proposed here unites evidence from archaeology, mitochondrial DNA, and Y-chromosomal DNA.
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Siegel, J. M. (2008). Do all animals sleep? Trends in Neurosciences, 31(4), 208–213.
Abstract: Some animals never exhibit a state that meets the behavioral definition of sleep. Others suspend or greatly reduce ‘sleep’ behavior for many weeks during the postpartum period or during seasonal migrations without any consequent ‘sleep debt.’ Rats die from one form of sleep deprivation, but sleep loss has not been shown to cause death in well-controlled studies in other vertebrate species. Some marine mammal species do not show evidence for REM sleep, and convincing evidence for this state in reptiles, fish and insects is lacking. The enormous variation in the nature of rest and sleep states across the animal kingdom and within the mammalian class has important implications for understanding the evolution and functions of sleep.
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Proops, L., & McComb, K. (2012). Cross-modal individual recognition in domestic horses (Equus caballus) extends to familiar humans. Proceedings of the Royal Society B: Biological Sciences, 279(1741), 3131–3138.
Abstract: It has recently been shown that some non-human animals can cross-modally recognize members of their own taxon. What is unclear is just how plastic this recognition system can be. In this study, we investigate whether an animal, the domestic horse, is capable of spontaneous cross-modal recognition of individuals from a morphologically very different species. We also provide the first insights into how cross-modal identity information is processed by examining whether there are hemispheric biases in this important social skill. In our preferential looking paradigm, subjects were presented with two people and playbacks of their voices to determine whether they were able to match the voice with the person. When presented with familiar handlers subjects could match the specific familiar person with the correct familiar voice. Horses were significantly better at performing the matching task when the congruent person was standing on their right, indicating marked hemispheric specialization (left hemisphere bias) in this ability. These results are the first to demonstrate that cross-modal recognition in animals can extend to individuals from phylogenetically very distant species. They also indicate that processes governed by the left hemisphere are central to the cross-modal matching of visual and auditory information from familiar individuals in a naturalistic setting.
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Covalesky, M. E., Russoniello, C. R., & Malinowski, K. (1992). Effects of show-jumping performance stress on plasma cortisol and lactate concentrations and heart rate and behavior in horses. Journal of Equine Veterinary Science, 12(4), 244–251.
Abstract: Summary Effects of show jumping competition on stress levels in horses was examined. Twenty-six homes were sampled in both show and farm environments from three levels of show experience schooling, (least experience, n=11); intermediate, (moderate experience, n=6); open, (most experience, n=9). Blood samples were taken at 6 time points; 3 at the horse show and 3 at the home farm (baseline at rest, pre-schooling and post-performance over a jump course). Stress responses were assessed through comparison of the behavioral response of the horses (determined by a subjective scoring system) to plasma cortisol (F) concentrations. Physical exertion was evaluated by heart rate (HR) and plasma lactate (L) concentrations. Schooling jumpers displayed higher baseline F concentrations than open jumpers (83g±9.2 vs 46.4±10.2 ng/ml, respectively; p<.05); but not when compared to intermediate jumpers (66.2 ± 13.7 ng/ml; p>.05) at the horse show. At the farm, there were no differences in F concentrations between experience levels at a time point (p<.05). Least experienced horses displayed higher F values at rest at the show compared to the home farm. At the show, open jumpers had higher L concentrations post-exercise compared to intermediate horses (40.3±3.4 vs 25.5±4.0 mg/dL, respectively; p<.05); but were not different compared to schooling jumpers (34.8±2.0 mg/dL; p>.05). There were no differences in heart rates or behavior score between experience levels at specific time points at either the show or farm (p>.05). Low positive correlations were found between HR and F (r=.24, p<.05); HR and L (r-.48, p<.05); and HR and behavior (r=.22, p<.05). Results suggest that conditioned jumpers that have previously been exposed to horse show environments do not appear stressed during acute show-jumping competition.
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Schneider, A. - C., Melis, A. P., & Tomasello, M. (2012). How chimpanzees solve collective action problems. Proceedings of the Royal Society B: Biological Sciences, .
Abstract: We presented small groups of chimpanzees with two collective action situations, in which action was necessary for reward but there was a disincentive for individuals to act owing to the possibility of free-riding on the efforts of others. We found that in simpler scenarios (experiment 1) in which group size was small, there was a positive relationship between rank and action with more dominant individuals volunteering to act more often, particularly when the reward was less dispersed. Social tolerance also seemed to mediate action whereby higher tolerance levels within a group resulted in individuals of lower ranks sometimes acting and appropriating more of the reward. In more complex scenarios, when group size was larger and cooperation was necessary (experiment 2), overcoming the problem was more challenging. There was highly significant variability in the action rates of different individuals as well as between dyads, suggesting success was more greatly influenced by the individual personalities and personal relationships present in the group.
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Melis, A. P., Warneken, F., Jensen, K., Schneider, A. - C., Call, J., & Tomasello, M. (2011). Chimpanzees help conspecifics obtain food and non-food items. Proceedings of the Royal Society B: Biological Sciences, 278(1710), 1405–1413.
Abstract: Chimpanzees (Pan troglodytes) sometimes help both humans and conspecifics in experimental situations in which immediate selfish benefits can be ruled out. However, in several experiments, chimpanzees have not provided food to a conspecific even when it would cost them nothing, leading to the hypothesis that prosociality in the food-provisioning context is a derived trait in humans. Here, we show that chimpanzees help conspecifics obtain both food and non-food items—given that the donor cannot get the food herself. Furthermore, we show that the key factor eliciting chimpanzees' targeted helping is the recipients' attempts to either get the food or get the attention of the potential donor. The current findings add to the accumulating body of evidence that humans and chimpanzees share the motivation and skills necessary to help others in situations in which they cannot selfishly benefit. Humans, however, show prosocial motives more readily and in a wider range of contexts.
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van Breda, E. (2006). A non-natural head-neck position (rollkur) during training results in less acute stress in elite trained dressage horses. Journal of Applied Animal Welfare Science, 9(1), 59–64.
Abstract: This study measured parameters of stress in recreational, trained horses (REC; n = 7) and elite (International Grand Prix level) trained, dressage horses (DRES; n = 5). The training of the DRES horses uses an unnatural head?neck position (Rollkur), whereas in the REC horses such training techniques are not common. The study measured stress by using heart rate variability analysis for 30 min postfeeding in the morning and 30 min postexercise after a morning training session. The study found no significant difference at rest between the REC and DRES horses. During the posttraining measurements, however, the DRES horses showed, among others, a less sympathetic and increased parasympathetic dominance. These results suggest that DRES horses tend to have less acute stress than do REC horses postexercise. The findings of this study suggest maintaining the health and well-being of DRES horses despite nonnatural, biomechanical positions.
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Goodson, J. L., Schrock, S. E., Klatt, J. D., Kabelik, D., & Kingsbury, M. A. (2009). Mesotocin and Nonapeptide Receptors Promote Estrildid Flocking Behavior. Science, 325(5942), 862–866.
Abstract: Proximate neural mechanisms that influence preferences for groups of a given size are almost wholly unknown. In the highly gregarious zebra finch (Estrildidae: Taeniopygia guttata), blockade of nonapeptide receptors by an oxytocin (OT) antagonist significantly reduced time spent with large groups and familiar social partners independent of time spent in social contact. Opposing effects were produced by central infusions of mesotocin (MT, avian homolog of OT). Most drug effects appeared to be female-specific. Across five estrildid finch species, species-typical group size correlates with nonapeptide receptor distributions in the lateral septum, and sociality in female zebra finches was reduced by OT antagonist infusions into the septum but not a control area. We propose that titration of sociality by MT represents a phylogenetically deep framework for the evolution of OT’s female-specific roles in pair bonding and maternal functions.
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McComb, K., Shannon, G., Durant, S. M., Sayialel, K., Slotow, R., Poole, J., et al. (2011). Leadership in elephants: the adaptive value of age. Proc. R. Soc. Lond. B., 278(1722), 3270–3276.
Abstract: The value of age is well recognized in human societies, where older individuals often emerge as leaders in tasks requiring specialized knowledge, but what part do such individuals play in other social species? Despite growing interest in how effective leadership might be achieved in animal social systems, the specific role that older leaders may play in decision-making has rarely been experimentally investigated. Here, we use a novel playback paradigm to demonstrate that in African elephants (Loxodonta africana), age affects the ability of matriarchs to make ecologically relevant decisions in a domain critical to survival—the assessment of predatory threat. While groups consistently adjust their defensive behaviour to the greater threat of three roaring lions versus one, families with younger matriarchs typically under-react to roars from male lions despite the severe danger they represent. Sensitivity to this key threat increases with matriarch age and is greatest for the oldest matriarchs, who are likely to have accumulated the most experience. Our study provides the first empirical evidence that individuals within a social group may derive significant benefits from the influence of an older leader because of their enhanced ability to make crucial decisions about predatory threat, generating important insights into selection for longevity in cognitively advanced social mammals.
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