Abstract: To date, a large amount of equine genetic data has been obtained regarding (i) extant domestic horses of various breeds from all over the world, (ii) ancient domestic horses, (iii) the extant Przewalski's wild horse, and (iv) the late Pleistocene wild horse from Eurasia and North America. Here, a review of mtDNA and Y chromosome marker analyses is presented in the context of horse domestication. High matrilineal (mtDNA) diversity, which can be found in both extant and ancient (domestic and wild) horses, has suggested that a high number of wild (and tamed) mares were domesticated. Alternatively, Y chromosome marker analysis revealed a single haplotype in all domestic horses analyzed; interestingly even a small population of extant Przewalski's wild horses showed two different Y chromosome haplotypes. It seems that an extreme male population bottleneck occurred due to domestication, while reduction in the female population was only moderate, leaving about 100 distinct haplotypes. For this reason, we speculate that domestication might have started when the appropriate stallion was found or was obtained by selection. Perhaps it had some unusual but special characteristics which could have accelerated the process of domestication. We doubt that only a single Y chromosome haplotype will be found in present-day domestic horses if there are no important differences between the founder stallion/s and the other stallions that were not included in the domestication. In the Eneolithic, tamed and wild mares have probably been spread all over Eurasia, although the number of animals was most likely very low and the populations were limited to a restricted area (e.g., taming centers). Only two subspecies of wild horses (Tarpan and Przewalski's wild horse) have survived up to recently. During the further process of domestication, mares (tamed or wild) were preferentially crossed to stallions having more desirable characteristics. We assume that mares from different regions varied in their morphology due to adaptation to their local environmental conditions. These data might explain rapid expansion of horse populations, as well as their rapid differentiation into various phenotypes during the early phase of domestication.

Abstract: The article by Zucca and Sovrano (2008, this issue) represents part of a new wave of studies of lateralization in nonhuman species. This work is often in conflict with earlier studies of human cerebral asymmetry and handedness, and the associated claim that these asymmetries are uniquely human, and perhaps even a result of the “speciation event” that led to modern humans. It is now apparent that there are close parallels between human and nonhuman asymmetries, suggesting that they have ancient roots. I argue that asymmetries must be seen in the context of a bilaterally symmetrical body plan, and that there is a balance to be struck between the adaptive advantages of symmetry and asymmetry. In human evolution, systematic asymmetries were incorporated into activities that probably are unique to our species, but the precursors of these asymmetries are increasingly evident in other species, including frogs, fish, birds, and mammals – especially primates.

Abstract: There are numerous reports of novel learned behaviour patterns in animal populations, yet the factors influencing the invention and spread of these innovations remain poorly understood. Here we investigated to what extent the pattern of spread of innovations in captive groups of starlings, Sturnus vulgaris, could be predicted by knowledge of individual and social group variables, including association patterns, social rank orders, measures of neophobia and asocial learning performance. We presented small groups of starlings with a series of novel extractive foraging tasks and recorded the latency for each bird to contact and solve each task, as well as the orders of contacting and solving. We then explored which variables best predicted the observed diffusion patterns. Object neophobia and social rank measures characterized who was the first of the group to contact the novel foraging tasks, and the subsequent spread of contacting tasks was associated with latency to feed in a novel environment. Asocial learning performance, measured in isolation, predicted who was the first solver of the novel foraging tasks in each group. Association patterns did not predict the spread of solving. Contact latency and solving duration were negatively correlated, consistent with social learning underlying the spread of solving. Our findings indicate that we can improve our understanding of the diffusion dynamics of innovations in animal groups by investigating group-dependent and individual variables in combination. We introduce novel methods for exploring predictors of the origin and spread of behavioural innovations that could be widely applied.

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.

Abstract: Learning to associate sensory cues with threats is critical for minimizing aversive experience. The ecological benefit of associative learning relies on accurate perception of predictive cues, but how aversive learning enhances perceptual acuity of sensory signals, particularly in humans, is unclear. We combined multivariate functional magnetic resonance imaging with olfactory psychophysics to show that initially indistinguishable odor enantiomers (mirror-image molecules) become discriminable after aversive conditioning, paralleling the spatial divergence of ensemble activity patterns in primary olfactory (piriform) cortex. Our findings indicate that aversive learning induces piriform plasticity with corresponding gains in odor enantiomer discrimination, underscoring the capacity of fear conditioning to update perceptual representation of predictive cues, over and above its well-recognized role in the acquisition of conditioned responses. That completely indiscriminable sensations can be transformed into discriminable percepts further accentuates the potency of associative learning to enhance sensory cue perception and support adaptive behavior.