Antioxidants, showy males and sperm quality

The fertility of males sometimes correlates with their ornamental display, but we do not have a mechanistic explanation to universally link these traits. We suggest that both sperm quality (fertility; integrity of DNA), and the substrates responsible for male ornamentation, may be vulnerable to free radical attack, which can be mitigated by antioxidants. Support for these ideas is at present weak, and requires validation in ecological contexts. We hypothesize that a link between ornamentation and sperm quality could arise if antioxidants are in limited supply, and the showiest males may be preferred because they are most likely to be fertile, or to provide sperm with undamaged genotypes that could give rise to fit offspring.     

Testosterone,status, and mood in human males

Experimental literature on nonhuman primates indicates that a male's testosterone level changes when his status changes, rising when he achieves or defends a dominant position, and falling when he is dominated. Three experiments are reported which test for a similar effect among adult human males. In the first experiment, subjects played in doubles tennis matches in which winners received prizes of $ 100 apiece. Most winners of matches who had decisive victories showed subsequent rises in testosterone relative to losers of these matches; however, the winners of one very close match, in which there was no clear cut triumph, did not show testosterone rises. In the second experiment, subjects won $100 prizes, or not, depending on the random draw of a lottery. Winners in this situation, where their fortunes came without any effort of their own, did not show subsequent testosterone rises which were greater than those of losers. The third experiment used the natural setting of a medical school graduation. Rises in testosterone were observed among new recipients of the M.D. degree 1 and 2 days after the ceremony. In these experiments, changes in testosterone showed some relationship to subjects' moods. These results suggest that when a man achieves a rise in status through his own efforts, and he has an elation of mood over the achievement, then he is likely to have a rise in testosterone.     

Prolactin, fatherhood, and reproductive behavior in human males

Although humans are considered unusual among mammals for the intensity of care that fathers often provide offspring, little is known about the hormonal architecture regulating human paternal investment. Prolactin has important reproductive functions in both female and male mammals and other taxa, making it a candidate regulator of human paternal behavior. Notably, prolactin is higher during periods of offspring care in some species, but it is unknown if this pattern occurs in human fathers. We draw on a sample of men (n = 289; age 21-23 at baseline) from Metropolitan Cebu City, Philippines to evaluate relationships between prolactin, assayed from dried blood spots, and components of reproductive behavior and relationship status. In this sample, fathers had higher prolactin than nonfathers (P = 0.006), and fathers of infants had borderline higher prolactin than fathers of older children (P = 0.054). Among single nonfathers at baseline (2005), baseline prolactin did not predict who transitioned to fatherhood by follow-up 4.5 years later. Among nonfathers, men with greater prolactin reported more lifetime sexual partners (P = 0.050) as well as more sexual activity in the month before sampling (P = 0.060). Our results suggest that fathers in Cebu have higher prolactin than nonfathers, with hormone levels highest among fathers of young infants. Although these findings are generally consistent with evidence from other species for pronurturing effects of prolactin, evidence for positive relationships between the hormone and measures of sexual behavior at Cebu point to likely complexities in the hormone's involvement in male reproductive strategy.     

Race, health, and disease in 19th-century-born males

This study analyzed skeletal health disparities among African American and Euro-American males of low socioeconomic status born between 1825 and 1877. A total of 651 skeletons from the Cobb, Hamann-Todd, and Terry anatomical collections were macroscopically examined for skeletal pathologies related to dietary deficiencies and disease. Individuals were separated into age, ancestry, birth (Antebellum, Civil War, Pre-Reconstruction, and Reconstruction), combined ancestry/birth, enslaved versus liberated, and collection cohorts. These groups were statistically evaluated using ANOVA and χ(2) analyses to determine if age, ethnic, and temporal differences existed. Results indicated that African Americans, especially those born during Reconstruction, had significantly higher frequencies of tuberculosis (P = 0.004) and treponematosis (P = 0.006) than Euro-Americans. Historical sources are important in contextualizing why these different ethnic and temporal patterns were present, pointing to environmental conditions related to enslavement, postliberation migration to the industrialized North, crowded urban living conditions, and poor sanitation.     

Serotonin contents in the hypothalamus of adult males, females and males castrated during the neonatal period

The aim of the present work was to study the character of the change in serotonin level in the anterior and medial basal hypothalamus of adult rats after the effect of testicular hormones had been switched off on the first day of postnatal life. It was shown in our work that in males serotonin level was significantly lower than that in females by 67 and 46% in the anterior and medial basal hypothalamus, respectively. Castration of newborn males resulted in a significant increase in serotonin level in both anterior and medial basal hypothalamus-up to the level observed in females. It is supposed that the male sex hormones affect differentiation of serotoninergic system of the brain.     

Testosterone,physical activity,and somatic outcomes among Filipino males

Testosterone (T) facilitates male investment in reproduction in part through its anabolic effects on skeletal muscle. Traits like muscle and strength are energetically costly but are believed to enhance competitive ability in humans and other mammals. However, there are limited data on relationships between T and somatic outcomes in lean, non‐western populations. We evaluate relationships between waking and pre‐bed salivary T and adiposity, fat‐free mass (FFM), arm muscle area (AMA), and grip strength (GS) in a large, population‐based birth cohort of young adult Filipino males (20.8–22.6 years, n = 872). Data were collected as part of the Cebu Longitudinal Health and Nutrition Survey. Neither waking nor evening T predicted FFM, AMA, or GS. However, there were borderline or significant interactions between T and basketball playing (the most common team sport) and weight lifting as predictors of outcomes: higher waking T predicted higher FFM (activity × T interaction P < 0.01), AMA (interaction P < 0.1), and GS (interaction P < 0.02) among frequent basketball players, and GS (interaction P < 0.09) among the smaller sample of weight lifters. In contrast to clinical studies, but consistent with findings in several subsistence‐level populations, T was positively related to adiposity in these lean young males, suggesting that energy status might regulate circulating T. Our findings support a role of the prewaking rise in T as a determinant of energetic allocation to lean mass and strength in the context of repeated muscular use and support the hypothesized role of T as a mediator of investment in costly somatic traits in human males. Am J Phys Anthropol 142:590–599, 2010. © 2010 Wiley‐Liss, Inc.     

Diurnal patterns of testosterone, dihydrotestosterone, estradiol, and cortisol in serum of rhesus males: Relationship to sexual behavior in aging males

This study was carried out to determine differences between old and young rhesus males in levels and diurnal patterns of testosterone, dihydrotestosterone, cortisol, and estradiol, and to determine correlations between these hormones and sexual behavior of the old males. Blood was drawn from old (n = 9) and young (n = 9) rhesus males over 5 consecutive days at 0900, 1300, and 2100 hr. The two groups of males did not differ in mean serum levels of testosterone, dihydrotestosterone, or estradiol at any time. Although the old and young did not differ in cortisol levels at 0900 and 1300 hr, the cortisol levels at 2100 hr were lower in the old males. Diurnal variations in testosterone, dihydrotestosterone, and cortisol were comparable in old and young males. Mean serum levels of estradiol were significantly higher at 0900 hr than at 1300 hr in the old males, whereas in the young males estradiol levels did not differ with time of day. There was a significant positive correlation between testosterone and yawning rate, and cortisol levels were correlated positively with rate of contacting, rate of mounting, and percentage of tests with erections. The decline in sexual performance of old rhesus males cannot be attributed to changes in the levels or diurnal patterns of testosterone, dihydrotestosterone, or estradiol, but lower cortisol levels in old males may contribute to the decline in sexual behavior.     

Follow-up 20 years later of 34 Klinefelter males with karyotype 47,XXY and 16 hypogonadal males with karyotype 46,XY

Summary A 20-year follow-up study of 50 hypogonadal males has been made. Of these 34 had Klinefelter's syndrome with the karyotype 47,XXY and 16 had the karyotype 46,XY. These males have been examined at mean ages of 27 and 37 and in the present study at a mean age of 47. At the first examination the following conditions were found in the Klinefelter males to a significantly higher degree than in the hypogonadal males with 46,XY: immaturity, below average school performance, few or no friends, previous mental illness, little energy and initiative, few or no spare time interests, occupation as an unskilled labourer. Psychological testing showed a full scale IQ of 103 in the Klinefelter males and 115 in the hypogonadal males. The follow-up studies have shown that in spite of these findings the Klinefelter males have managed far better than could have been expected at the time of the first investigation. The improvement in a number of conditions such as mental health, working capacity, social adjustment, relations with other people, and activity level was considerable between the ages of 27 and 37. The present examination shows a further improvement at the age of 47 with the only significant difference between the Klinefelter males and the hypogonadal males with 46,XY being a higher frequency of single Klinefelter males. The present examination also showed that there was no significant difference between the two groups in occupation, working capacity, social adjustment, mental and physical disorders or criminality. The results of the examination at the mean age of 27 would probably have been considerably more favourable for the Klinefelter males if diagnosis had been made in childhood, and information, counselling, support and hormone treatment had been given from an early age. The fact that the great majority of the Klinefelter males have managed quite well in spite of this and that no remarkable differences were found between them and a control group is of great importance for genetic counsellers, especially for prenatal counsellers. Up until now, in 75% of cases in which sex chromosome abnormalities, including Klinefelter's syndrome, have been diagnosed prenatally in Denmark abortion has been induced. We believe this is mainly due to insufficient information about the many positive aspects of the development of individuals with sex chromosome abnormalities.     

Incidence of 47,XYY males: Implications of the production of 47,XYY offspring by 47,XYY males

Abstract

Chromosomally normal 46,XY males can have 47,XYY male offspring as a result of fertilization of a normal ovum by a YY spermatozoon, produced by nondisjunction in the second meiotic division or by mitotic nondisjunction of the Y chromosome in early stages of embryonic development of a 46,XY fetus. If such meiotic and mitotic nondisjunctions were random events and if these were the only source of 47,XYY males in the population, the incidence of 47,XYY males would remain constant. Two cases have been reported, however, in which 47,XYY males produced 47,XYY male offspring. If there are 47,XYY males who are a source of 47,XYY males in the population, there is the possibility that the incidence of 47,XYY males is changing. A discrete‐generation model is presented which describes (1) the change in incidence of 47,XYY males from one generation to the next; (2) the incidence at equilibrium; and (3) the incidence as a function of the probability that a 47.XYY male has a 47,XYY offspring, and as a function of the mean number of offspring of 47,XYY males relative to the mean number of offspring of 46,XY males.     

Oriented flight responses of female Mediterranean fruit flies to calling males, odor of calling males, and a synthetic pheromone blend

Male Mediterranean fruit flies,Ceratitis capitata (Wiedemann), produce volatile chemicals thought to be attractive sex pheromones. We demonstrated for the first time that male odor elicits upwind flight and zigzagging upwind flight patterns in mature unmated females. Such flight patterns indicate the mechanisms involved in female location of the pheromone source and arrival at that source. Similar female oriented upwind flight responses occurred with a three component blend comprised of ethyl-(E)-octenoate, geranyl acetate, andE,E-alpha farnesene. These findings clarify the role of male sex pheromone in mate-location strategies in this species and provide new bioassay criteria for evaluating attraction responses to male pheromone and synthetic blends.     

Pubertal timing, hormones, and body composition among adolescent Turkana males

The Turkana, like other East African pastoral groups, are known for their tall adult stature, achieved despite a blunted growth spurt during adolescence and continued growth into the early 20s. To investigate the hormonal mechanisms associated with the pattern of slow and continued adolescent growth, we collected data on hormonal status, height, weight, and trunk skinfolds and ethnographic self-reports of testicular maturation in a cross-sectional sample of 35 nomadic and 37 settled Turkana males aged 14-24. Hormonal determinations included testosterone (T), sex hormone-binding globulin (SHBG), and dehydroepiandrosterone (DHEA) in blood, in addition to urinary DHEA. Self-reports of testicular maturation showed no difference between settled and nomadic subpopulations. However, nomadic boys exhibited significantly higher levels of T, DHEA, and SHBG. Of all the hormones, only SHBG showed a significant relationship with age. Multiple regression models show blood T and SHBG to be significant independent predictors of achieved height as well as weight, controlling for age. Our results suggest that onset of puberty is substantially delayed among Turkana males, and that bioavailable T is related to growth in stature during adolescence. We suggest that SHBG acts to mediate the effects of energy availability on adolescent growth in this energetically limited population. Our findings may also have implications for understanding adolescent growth among Homo erectus.     

Prudent males,group adaptation,and the tragedy of the commons

For almost five decades three threads have coexisted in the evolutionary and ecological literature, with their links only recently becoming visible and some of them still not properly addressed. These are the levels of selection debate, the metaphor of the tragedy of the commons, and the evolutionary study of sexual conflict. We analyze the eco‐evolutionary dynamics of a curious system where an asexual all‐female fish species (the Amazon molly Poecilia formosa) requires sperm from other species as a developmental trigger, without utilizing the genes from sperm. The dynamics of such a system bear strong resemblance to host–parasite dynamics, and populations of the sexual ‘host’ species persist much better if males avoid mating with Amazons. However, such avoidance may compromise their current mating success, and if this is the case, prudent mating becomes an altruistic trait that helps to keep an accumulating problem of a competing species at bay, and Amazon‐free space can be seen to form a common good that a population should maintain for future generations. A model shows that the evolution of altruistic mating restraint is possible but selection for short‐term gains means that it will remain less than perfect. This helps to explain why the anomalous gynogenetic system can persist, but it also raises questions about what kinds of traits can be classified as adaptations when optimization is not perfect and traits evolve to achieve short‐term goals better than long‐term performance. Contributing to the levels of selection debate, we encourage researchers to study the implications of the different timescales involved in the eco‐evolutionary process.     

The origin of 45,X males.

Maleness in association with the karyotype 45,X is a very rare and hitherto unexplained condition previously described in only four or five patients. This study was carried out to determine whether such males might actually possess Y-chromosomal material. Of the two 45,X males studied, one was found to be a low-grade mosaic with a 46,XY karyotype in less than 3% of fibroblasts; all lymphocytes karyotyped were 45,X. Fibroblast DNA from this individual was found to contain Y-specific repeated sequences in 1%-3% the amount observed in the father, consistent with mosaicism for a 46,XY cell line. No Y-specific repeated sequences were detected in the other patient, in whom all mitoses were 45,X. In neither patient were there detectable amounts of any of the single-copy Y-specific DNA sequences for which we tested. Studies of Xg blood groups and of X-linked restriction fragment length polymorphisms indicated that the single X chromosome was of maternal origin in both 45,X male probands. In contrast to the situation in XX males, we can exclude paternal X-Y interchange as the etiology in the cases described here. Our findings are compatible with mosaicism being the explanation of at least some "45,X" males.     

Predation, sensitivity, and sex: why female black rhinoceroses outlive males

Among sexually dimorphic, polygynous mammals, adult femalestend to outlive males and respond more strongly to predatorsthan males. We asked whether a monomorphic, polygynous speciesvirtually immune to predation due to large size (black rhinoceros,Diceros bicornis) conforms to this pattern. Data on 193 interactionswith lions (Panthera leo) and spotted hyenas (Crocuta crocuta)in two nonhabituated populations in Namibia studied from 1991to 1993 revealed that: (1) females were more vigilant or aggressivethan males to either of the potential predators; and (2) whethersolitary or with calves, females attacked more often than males.Although solitary females tended to be more aggressive to lionsthan to hyenas, neither females with calves or males seemedto discriminate between the two carnivores. We also simulatedthe behavior of human predators (poachers) during 69 encounterswith rhinoceroses. While both sexes abandoned local sites becauseof our presence, females ran farther than males, covering upto 40 km in a day. These findings implicate a behavioral mechanismto explain why secondary sex ratios favor females - males aremore prone to human predation, a prediction consistent withdata from 12 populations throughout Africa. Black rhinocerosesappear to be an unanticipated exception to the well-establishedpattern of male-biased mortality in polygynous mammals; in theabsence of intense human predation (a recent event), male mortalityfails to exceed that of females, suggesting that intrasexualcompetition in a polygynous mammal: may not be the primary causeof unbalanced secondary sex ratios. Our results on the causesof sex differences in mortality and in responsiveness to differentpredators reinforce the relevance of behavioral ecology to conservation;such information is necessary for planning how best to minimizenegative human influences on the few remaining wild Africanrhinos.