Human Ability to Recognize Kin Visually Within Primates
Alexandra Avergne et al.; 2009
http://link.springer.com/article/10.1007/s10764-009-9339-0/fulltext.html
Abstract
The assessment of relatedness is a key determinant in the evolution of social behavior in primates. Humans are able to detect kin visually in their own species using facial phenotypes, and facial resemblance in turn influences both prosocial behaviors and mating decisions. This suggests that cognitive abilities that allow facial kin detection in conspecifics have been favored in the species by kin selection. We investigated the extent to which humans are able to recognize kin visually by asking human judges to assess facial resemblance in 4 other primate species (common chimpanzees, western lowland gorillas, mandrills, and chacma baboons) on the basis of pictures of faces. Humans achieved facial interspecific kin recognition in all species except baboons. Facial resemblance is a reliable indicator of relatedness in at least chimpanzees, gorillas, and mandrills, and future work should explore if the primates themselves also share the ability to detect kin facially.
Mittwoch, 30. Oktober 2013
Low fertility increases descendant socioeconomic position but reduces long-term fitness in a modern post-industrial society
Low fertility increases descendant socioeconomic position but reduces long-term fitness in a modern post-industrial society
Anna Goodman et al.; 2012
Abstract
Adaptive accounts of modern low human fertility argue that small family size maximises the inheritance of socioeconomic resources across generations and may consequently increase long-term fitness. This paper explores the long-term impacts of fertility and socioeconomic position (SEP) on multiple dimensions of descendant success in a unique Swedish cohort of 14,000 individuals born 1915-1929. We show that low fertility and high SEP predict increased descendant socioeconomic success across four generations. Furthermore, these effects are multiplicative, with the greatest benefits of low fertility observed when SEP is high. Low fertility and high SEP do not, however, predict increased descendant reproductive success. Our results are therefore consistent with the idea that modern fertility limitation represents a strategic response to the local costs of rearing socioeconomically competitive offspring, but contradict adaptive models suggesting that it maximises long-term fitness. This indicates a conflict in modern societies between behaviours promoting socioeconomic versus biological success. This paper also makes a methodological contribution, demonstrating that number of offspring strongly predicts long-term fitness and thereby validating use of fertility data to estimate current selective pressures in modern populations. Finally our findings highlight that differences in fertility and SEP have important long-term effects on the persistence of social inequalities across generations.
-------------------------------------------------------------------------------------------------------------
"We do, however, find strong support for the prediction that fertility limitation in modern societies enhances descendant socioeconomic success. Thus, our results indicate that reproductive behaviours that promote biological success (i.e. long-term genetic fitness) are in conflict with those that promote descendant socioeconomic success in modern populations. Specifically, we find that both low parental fertility and high parental SEP independently predict higher schoolmarks, educational level and income, and this is generally true in male and female descendants alike ... . Moreover, these associations persist up to at least the great-grandchild generation, reflecting the advantage of starting one’s own offspring on a favourable socioeconomic trajectory.
We also demonstrate for the first time a multigenerational interaction between SEP and fertility, such that the socioeconomic benefit of low fertility was especially large in groups that already had high SEP. This finding adds to a number of recent studies indicating that demographic modernization is associated with increased socioeconomic pay-offs to fertility limitation for the wealthiest families ... ."
Anna Goodman et al.; 2012
Abstract
Adaptive accounts of modern low human fertility argue that small family size maximises the inheritance of socioeconomic resources across generations and may consequently increase long-term fitness. This paper explores the long-term impacts of fertility and socioeconomic position (SEP) on multiple dimensions of descendant success in a unique Swedish cohort of 14,000 individuals born 1915-1929. We show that low fertility and high SEP predict increased descendant socioeconomic success across four generations. Furthermore, these effects are multiplicative, with the greatest benefits of low fertility observed when SEP is high. Low fertility and high SEP do not, however, predict increased descendant reproductive success. Our results are therefore consistent with the idea that modern fertility limitation represents a strategic response to the local costs of rearing socioeconomically competitive offspring, but contradict adaptive models suggesting that it maximises long-term fitness. This indicates a conflict in modern societies between behaviours promoting socioeconomic versus biological success. This paper also makes a methodological contribution, demonstrating that number of offspring strongly predicts long-term fitness and thereby validating use of fertility data to estimate current selective pressures in modern populations. Finally our findings highlight that differences in fertility and SEP have important long-term effects on the persistence of social inequalities across generations.
-------------------------------------------------------------------------------------------------------------
"We do, however, find strong support for the prediction that fertility limitation in modern societies enhances descendant socioeconomic success. Thus, our results indicate that reproductive behaviours that promote biological success (i.e. long-term genetic fitness) are in conflict with those that promote descendant socioeconomic success in modern populations. Specifically, we find that both low parental fertility and high parental SEP independently predict higher schoolmarks, educational level and income, and this is generally true in male and female descendants alike ... . Moreover, these associations persist up to at least the great-grandchild generation, reflecting the advantage of starting one’s own offspring on a favourable socioeconomic trajectory.
We also demonstrate for the first time a multigenerational interaction between SEP and fertility, such that the socioeconomic benefit of low fertility was especially large in groups that already had high SEP. This finding adds to a number of recent studies indicating that demographic modernization is associated with increased socioeconomic pay-offs to fertility limitation for the wealthiest families ... ."
Dienstag, 29. Oktober 2013
Attractive men induce testosterone and cortisol release in women
Attractive men induce testosterone and cortisol release in women
Hassan A Lopez et al.; 2009
Abstract
Recently, Roney et al. (Roney, J.R., Lukaszewski, A.W., Simmons, Z.L., 2007. Rapid endocrine responses of young men to social interactions with young women. Horm. Behav. 52, 326–33; Roney, J.R., Mahler, S.V., Maestripieri, D., 2003. Behavioral and hormonal responses of men to brief interactions with women. Evol. Hum. Behav. 24, 365–375) demonstrated that men release testosterone and cortisol in response to brief social interactions with young women. The current experiment examined whether women show a similar endocrine response to physically and behaviorally attractive men. 120 women (70 naturally-cycling and 50 using hormonal contraceptives) were shown one of four 20-minute video montages extracted from popular films, depicting the following scenarios: 1) an attractive man courting a young woman (experimental stimulus), 2) a nature documentary (video clip control), 3) an unattractive older man courting a woman (male control), and 4) an attractive woman with no men present (female control). Saliva samples were taken before and after presentation of the stimulus, and were later analyzed for testosterone and cortisol content via enzyme immunoassay. Naturally-cycling women experienced a significant increase in both testosterone and cortisol in response to the experimental stimulus but to none of the control stimuli. Participants taking hormonal contraceptives also showed a significant cortisol response to the attractive man. Women may release adrenal steroid hormones to facilitate courtship interactions with high mate-value men.
Hassan A Lopez et al.; 2009
Abstract
Recently, Roney et al. (Roney, J.R., Lukaszewski, A.W., Simmons, Z.L., 2007. Rapid endocrine responses of young men to social interactions with young women. Horm. Behav. 52, 326–33; Roney, J.R., Mahler, S.V., Maestripieri, D., 2003. Behavioral and hormonal responses of men to brief interactions with women. Evol. Hum. Behav. 24, 365–375) demonstrated that men release testosterone and cortisol in response to brief social interactions with young women. The current experiment examined whether women show a similar endocrine response to physically and behaviorally attractive men. 120 women (70 naturally-cycling and 50 using hormonal contraceptives) were shown one of four 20-minute video montages extracted from popular films, depicting the following scenarios: 1) an attractive man courting a young woman (experimental stimulus), 2) a nature documentary (video clip control), 3) an unattractive older man courting a woman (male control), and 4) an attractive woman with no men present (female control). Saliva samples were taken before and after presentation of the stimulus, and were later analyzed for testosterone and cortisol content via enzyme immunoassay. Naturally-cycling women experienced a significant increase in both testosterone and cortisol in response to the experimental stimulus but to none of the control stimuli. Participants taking hormonal contraceptives also showed a significant cortisol response to the attractive man. Women may release adrenal steroid hormones to facilitate courtship interactions with high mate-value men.
Testosterone responses to competition in men are related to facial masculinity
Testosterone responses to competition in men are related to facial masculinity
Nicholas Pound et al.; 2009
http://rspb.royalsocietypublishing.org/content/276/1654/153.full
Abstract
Relationships between androgens and the size of sexually dimorphic male traits have been demonstrated in several non-human species. It is often assumed that a similar relationship exists for human male faces, but clear evidence of an association between circulating testosterone levels and the size of masculine facial traits in adulthood is absent. Here we demonstrate that, after experimentally determined success in a competitive task, men with more a masculine facial structure show higher levels of circulating testosterone than men with less masculine faces. In participants randomly allocated to a ‘winning’ condition, testosterone was elevated relative to pre-task levels at 5 and 20 min post-task. In a control group of participants allocated to a ‘losing’ condition there were no significant differences between pre- and post-task testosterone. An index of facial masculinity based on the measurement of sexually dimorphic facial traits was not associated with pre-task (baseline) testosterone levels, but was associated with testosterone levels 5 and 20 min after success in the competitive task. These findings indicate that a man's facial structure may afford important information about the functioning of his endocrine system.
Nicholas Pound et al.; 2009
http://rspb.royalsocietypublishing.org/content/276/1654/153.full
Abstract
Relationships between androgens and the size of sexually dimorphic male traits have been demonstrated in several non-human species. It is often assumed that a similar relationship exists for human male faces, but clear evidence of an association between circulating testosterone levels and the size of masculine facial traits in adulthood is absent. Here we demonstrate that, after experimentally determined success in a competitive task, men with more a masculine facial structure show higher levels of circulating testosterone than men with less masculine faces. In participants randomly allocated to a ‘winning’ condition, testosterone was elevated relative to pre-task levels at 5 and 20 min post-task. In a control group of participants allocated to a ‘losing’ condition there were no significant differences between pre- and post-task testosterone. An index of facial masculinity based on the measurement of sexually dimorphic facial traits was not associated with pre-task (baseline) testosterone levels, but was associated with testosterone levels 5 and 20 min after success in the competitive task. These findings indicate that a man's facial structure may afford important information about the functioning of his endocrine system.
Behavioral and hormonal responses of men to brief interactions with women
Behavioral and hormonal responses of men to brief interactions with women
James R Roney et al.; 2003
Abstract
This study tested for behavioral and hormonal reactions of young men to brief social encounters with potential mating partners. Male college students were randomly assigned to engage in a short conversation with either a young man (male condition) or a young woman (female condition). Participants provided saliva samples before and after the conversation, completed a battery of psychological measures after the interaction, and had their behavior rated by their conversation partners. Salivary testosterone (T) increased significantly over baseline levels in the female condition only, though differences between conditions were not significant. In addition, change in T was significantly correlated with the degree to which the female confederates thought the male participants were trying to impress them. These behavioral ratings, in turn, were correlated with the participants’ ratings of the female confederates as potential romantic partners. Results were generally consistent with the hypothesis that human males may exhibit a behavioral and endocrine courtship response that is similar to that observed in males of many nonhuman vertebrate species.
James R Roney et al.; 2003
Abstract
This study tested for behavioral and hormonal reactions of young men to brief social encounters with potential mating partners. Male college students were randomly assigned to engage in a short conversation with either a young man (male condition) or a young woman (female condition). Participants provided saliva samples before and after the conversation, completed a battery of psychological measures after the interaction, and had their behavior rated by their conversation partners. Salivary testosterone (T) increased significantly over baseline levels in the female condition only, though differences between conditions were not significant. In addition, change in T was significantly correlated with the degree to which the female confederates thought the male participants were trying to impress them. These behavioral ratings, in turn, were correlated with the participants’ ratings of the female confederates as potential romantic partners. Results were generally consistent with the hypothesis that human males may exhibit a behavioral and endocrine courtship response that is similar to that observed in males of many nonhuman vertebrate species.
Montag, 28. Oktober 2013
Cigarette Smoking and Age at Natural Menopause
Cigarette Smoking and Age at Natural Menopause
David W Kaufman et al.; 1980
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1619390/pdf/amjph00677-0086.pdf
Abstract
In a cohort of 656 naturally postmenopausal women who were interviewed at age 60 to 69 years, and who had reached their menopause between the ages of 35 and 59 years, the mean age at menopause declined with increasing number of cigarettes smoked, from 49.4 years of age among women who had never smoked to 47.6 years of age among women who smoked at least 15 cigarettes per day (p < 0.02). The relationship was not attributable to the onset of menopause inducing women to take up smoking.
David W Kaufman et al.; 1980
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1619390/pdf/amjph00677-0086.pdf
Abstract
In a cohort of 656 naturally postmenopausal women who were interviewed at age 60 to 69 years, and who had reached their menopause between the ages of 35 and 59 years, the mean age at menopause declined with increasing number of cigarettes smoked, from 49.4 years of age among women who had never smoked to 47.6 years of age among women who smoked at least 15 cigarettes per day (p < 0.02). The relationship was not attributable to the onset of menopause inducing women to take up smoking.
Sonntag, 27. Oktober 2013
Abonnieren
Posts (Atom)