The evolution of language: a comparative review

For many years the evolution of language has been seen as a disreputable topic, mired in fanciful "just so stories" about language origins. However, in the last decade a new synthesis of modern linguistics, cognitive neuroscience and neo-Darwinian evolutionary theory has begun to make important contributions to our understanding of the biology and evolution of language. I review some of this recent progress, focusing on the value of the comparative method, which uses data from animal species to draw inferences about language evolution. Discussing speech first, I show how data concerning a wide variety of species, from monkeys to birds, can increase our understanding of the anatomical and neural mechanisms underlying human spoken language, and how bird and whale song provide insights into the ultimate evolutionary function of language. I discuss the ‘‘descended larynx’ ’ of humans, a peculiar adaptation for speech that has received much attention in the past, which despite earlier claims is not uniquely human. Then I will turn to the neural mechanisms underlying spoken language, pointing out the difficulties animals apparently experience in perceiving hierarchical structure in sounds, and stressing the importance of vocal imitation in the evolution of a spoken language. Turning to ultimate function, I suggest that communication among kin (especially between parents and offspring) played a crucial but neglected role in driving language evolution. Finally, I briefly discuss phylogeny, discussing hypotheses that offer plausible routes to human language from a non-linguistic chimp-like ancestor. I conclude that comparative data from living animals will be key to developing a richer, more interdisciplinary understanding of our most distinctively human trait: language

Factors affecting body temperatures of toads

Factors influencing levels and rates of variation of body temperature ( T b ) in montane Bufo boreas boreas and in lowland Bufo boreas halophilus were investigated as an initial step toward understanding the role of natural thermal variation in the physiology and energetics of these ectothermic animals. Body temperatures of boreas can vary 25–30° C over 24-h periods. Such variation is primarily due to both nocturnal and diurnal activity and the physical characteristics of the montane environment. Bufo boreas halophilus are primarily nocturnal except during breeding and are voluntarily active at body temperatures ranging between 10 and 25° C. Despite variation in T b encountered in the field, boreas select a narrow range of T b in a thermal gradient, averaging 23.5 and 26.2° C for fasted individuals maintained under field conditions or acclimated to 20° C, respectively. In a thermal gradient the mean T b of fasted halophilus acclimated to 20° C is 23.9° C. Skin color of boreas varies in the field from very dark to light. The dark skins absorb approximately 4% more radiation than the light ones. Light colored boreas should absorb approximately 5% more radiation than similarly colored halophilus . Evaporative water losses increase directly with skin temperatures and vapor pressure deficit in both subspecies. Larger individuals heat and cool more slowly than smaller ones. Calculation of an enery budget for boreal toads suggests that they could sit in direct sunlight for long periods without fatally overheating, providing the skin was continually moist.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/47722/1/442_2004_Article_BF00344732.pd

Sperm telomere length correlates with blood telomeres and body size in red-sided garter snakes, Thamnophis sirtalis parietalis

© 2020 The Zoological Society of London Telomeres, tandem repeats of TTAGGG at the ends of chromosomes, are highly dynamic structures that shorten in response to a variety of factors, including organismal stress and tissue-specific growth rates. Cell turnover rates are frequently linked to their functions, resource availability and telomere dynamics. Using male red-sided garter snakes, Thamnophis sirtalis parietalis, as a model, we investigated the relationship between telomere length in sperm cells, blood cells telomere length and a growth proxy (age-adjusted body length and mass). This relationship is interesting because snakes exhibit indeterminate growth and because these garter snakes have a dissociated reproductive cycle where spermatogenesis occurs months prior to the mating season. In this study, we determined sperm telomere length (STL) and male age using qPCR and skeletochronology, respectively. Sperm telomere length correlated positively with snout–vent length (SVL) and with age-adjusted SVL as a proxy for growth rate (residuals of size against age regression, hereafter growth), but not with age. Although an individual’s STL is correlated with blood telomere length (BTL), sperm telomeres are 60% longer than blood telomeres. In previous work, we have shown that BTL is shorter in older males and unrelated to SVL or any growth rate proxies. We hypothesized that STL is related to growth and SVL because growth and sperm production both occur during summer when resources are most abundant and stress lowest. This study is the first to compare telomere dynamics between cell types in a snake and supports growing evidence that telomere dynamics may be highly tissue-specific and driven by the life-history strategy of an organism