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Data from an urban sample of American women of reproductive ages demonstrate that age at menarche is correlated with age at first intercourse, that age at first intercourse is correlated with age at first pregnancy, and that menarche is therefore correlated with age at first pregnancy. This applied to both blacks and whites when examined for the early years of the reproductive cycle. Girls with early menarche, compared to those with late menarche, are more than twice as likely to have had intercourse by age 16, and almost twice as likely to have given birth or had a pregnancy terminated by age 18. It is therefore useful to think of the timing of menarche as an indicator of the probability of early intercourse and early childbearing.  相似文献   

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《Ibis》1945,87(2):224-249
An account is given of one hundred hours of observations at a Bateleur'a nest in north-eastern Tanganyike Territory. The adults were a white-backed bird and a chestnut-backed, with a sub-adult; probably over three years old, in association with them. The youngster took 130 dap to fledge. During at least part of the time all its food was brought by the white-backed adult. When the fledgling was about one month old its feeds averaged about one in eight hours; during its last week in the nest feeds were nearly three times as frequent.
Literature and unpublished data are reviewed in relation to special points of interest, viz.:—
Slow development and maturation accords with longevity. Fledging period apparently longer than authentically recorded for any land bird. First wing-moult may have started before first flight.
Tail length is greater in proportion to wing in juveniles than in adults.
Proportion of white-becks to chestnut-backs differs in parts of Africa, being least in South africa. White-tailed birds seem confined to Sudanese semi-desert belt.
Voice, flight habits and wing-noises seem to differ in parts of Africa.
Food comprises both carrion and live prey, especially snakes, but not poultry or other birds. Claws are not less sharp than those of Stephanoaëtus and Polemaëtus .
Breeding records in Tropical Africa show, when analysed with reference to egg-dates, that as a rule in each area the young get through their fledging period, or at least the later, unbrooded part, during the local cool dry season.
Psychologically the Bateleur is most peculiar: in the wild it is shy of man, sociable with big birdv of its own and other species, and breeding birds tolerate sub-adults: in captivity it becomes unusually tame, has a grecting ceremony for friends and likes to be handled.  相似文献   

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The debate over the improvement of moral capacity or moral enhancement through pharmacology has gained momentum in the last decade as a result of advances in neuroscience. These advances have led to the discovery and allowed the alteration of patterns of human behavior, and have permitted direct interventions on the neuronal structure of behavior. In recent years, this analysis has deepened regarding the anthropological foundations of morality and the reasons that would justify the acceptance or rejection of such technology. We present a review of proposals for pharmacological interventions directed directly towards moral enhancement. In addition, we identify the ethical dilemmas that such interventions may generate, as well as the moral assessment of the authors of these studies. There is a moderate consensus on the risks of any intervention on the intimate structure of the human condition, its autonomy and identity, but there are large differences in explaining the reasons for this concern and especially in justifying such interventions. These findings show that it is necessary to investigate the moral assessment of authors and the ethical dimension within the field of pharmacology in order to identify future trends.  相似文献   

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Sensitivity to pain and touch was measured in the nipple, areola, and cutaneous breast tissue of prepubertal boys and girls, postpubertal men and nuliparous women before and after delivery. Before puberty there were no differences between the sexes, but after puberty the tactile sensitivity of all areas of the women''s breast was significantly greater than the men''s. Tactil sensitivity of all areas also varied during the menstrual cycle, with maximal sensitivity at midcycle and at menstruation; the mid-cycle peak was absent when the women were taking oral contraceptives. But the most dramatic changes occured within 24 hours of parturition, when there was a great increase in breast sensitivity. This may be the key event for activating the suckling-induced discharge of oxytocin and prolactin and inhibiting ovulation during lactation.  相似文献   

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People across many societies routinely participate in physical or intellectual competitions in the absence of immediate substantial monetary or other apparent material rewards. But increased fame and social status associated with awards, such as the “Oscars”, need not be necessarily and solely a cultural construct unrelated to natural selection. Rather, prizes might be badges of honor if they are also honest indicators of evolutionary fitness. Analyses of reported reproductive success data, from a survey of well-known female and male actors, followed previously reported patterns of biological fitness in this sample of a human population. In addition, the numbers of Academy Awards received for acting were positively associated with reported numbers of biological children for both genders. The association of increased fitness with more awards received was statistically consistent even when considering that this subset of the population conformed to the Bateman effect in human reproduction: male actors had a more positive correlation than females between cumulative numbers of married partners and overall numbers of children. Honest signals of reproductive quality that are displayed by both sexes are expected to occur in humans and other species with costly biparental care and mutual mate choice.  相似文献   

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Media characterizations of zoo and aquarium animal deaths were randomly monitored on the internet for a 20‐month period (September 2003–May 2005). Based on 148 samples collected, it was possible to classify articles into one of four categories, which were operationally defined: 1) dispassionate observers; 2) accusers; 3) sympathizers; and 4) balancers. In addition, with the notable exception of seven cases, all of the articles examined focused on large, charismatic mammals, such as gorillas, dolphins, lions, and elephants. Although a majority of the articles examined (70.4%) were either dispassionate and objective or sympathetic, nearly a third (29.6%) were either accusatory or attempted to balance the accusatory statements of animal rights activists with sympathetic statements from zoo professionals. Recommendations are offered for how zoos should deal with the increasing media and public interest in zoo animal deaths, including: 1) a greater commitment to studying the reasons for mortality in a wide variety of species; and 2) an increased investment in record keeping and analysis, which should allow zoos to calculate average life spans in animal populations and to monitor and assess the risk of certain lethal diseases on a real‐time basis. Comparisons are drawn between zoo veterinary practices and human medicine, which are both inexact sciences. Suggestions are made for how the public and key decision‐makers can distinguish between media reports on zoo animal deaths that are legitimate cause for concern vs. those that are sensationalist and meant to generate controversy and sell papers. A greater focus on the science of zoo animal death is necessary for accredited zoos to maintain the public's confidence in their animal care practices. Zoo Biol 0:1–15, 2006. © 2006 Wiley‐Liss, Inc.  相似文献   

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The possible effects of migration and socio-economic status (SES) on age at menarche (MENA), age at menopause (MENO), potential reproductive period (PRP), and the correlation between MENA and MENO, were studied in 216 women in the Yucatan, Mexico. They were divided into three groups: migrant from the sisal-growing area on the coast, and sisal and coastal sedentary. Coastal sedentary women, living in the best socio-economic conditions, have the youngest MENA and the oldest MENO. Early migrant women have a significantly younger MENO (p.<0.05) and shorter PRP than Coastal sedentary women. There was no evidence of selective migration for MENA. When the Migrant, Sisal and Coastal sample were divided into cohorts by SES, it was impossible to obtain any clear picture. MENA increases with increased SES for the Coastal and Sisal cohorts, while the Migrant cohorts show an opposite trend. However, only the Low/Middle and High/Middle cohort differences for the Coastal sample are significant (p.<0.05, in both cases). It seems that migration has a limited affect on MENO and the PRP. Contrary to reports in the literature, the correlations between MENA and MENO and migrant status, and migrant socio-economic statuses, are negative, although these correlations were statistically significant in the Coastal sample.  相似文献   

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In a current article in the Journal of Vegetation Science, Molina‐Montenegro and colleagues extend the study of plant–plant interactions on stress gradients to extremes – the moss and lichen‐dominated communities of Antarctica. They found that the importance of facilitation at this extreme end of a ‘cold–harsh continuum’ was similar to that reported at the extreme ends of alpine gradients around the world. In other words, in contrast to recent theory and case studies in other systems, facilitative effects did not wane in extremely stressful conditions.  相似文献   

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Sirtuins are stress‐responsive proteins that direct various post‐translational modifications (PTMs) and as a result, are considered to be master regulators of several cellular processes. They are known to both extend lifespan and regulate spontaneous tumor development. As both aging and cancer are associated with altered stem cell function, the possibility that the involvement of sirtuins in these events is mediated by their roles in stem cells is worthy of investigation. Research to date suggests that the individual sirtuin family members can differentially regulate embryonic, hematopoietic as well as other adult stem cells in a tissue‐ and cell type‐specific context. Sirtuin‐driven regulation of both cell differentiation and signaling pathways previously involved in stem cell maintenance has been described where downstream effectors involved determine the biological outcome. Similarly, diverse roles have been reported in cancer stem cells (CSCs), depending on the tissue of origin. This review highlights the current knowledge which places sirtuins at the intersection of stem cells, aging, and cancer. By outlining the plethora of stem cell‐related roles for individual sirtuins in various contexts, our purpose was to provide an indication of their significance in relation to cancer and aging, as well as to generate a clearer picture of their therapeutic potential. Finally, we propose future directions which will contribute to the better understanding of sirtuins, thereby further unraveling the full repertoire of sirtuin functions in both normal stem cells and CSCs.  相似文献   

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