Did food increase fertility? Evaluation of !Kung and Herero history.

Low fertility among nomadic !Kung foragers of the northern Kalahari Desert of Botswana has been hypothesized to be an adaptation to scarcity of food. However, a comparison of !Kung fertility before and after a transition to a more sedentary lifestyle indicates that more food did not increase fertility. An examination of the fertility of neighboring sedentary Bantu-speaking Herero pastoralists during the same period also indicates that low female reproductive rates in this region are not unique to the !Kung. Herero fertility has increased dramatically in recent decades, probably in response to the control of sexually transmitted diseases in northwestern Botswana. More food appears to have substantially increased !Kung reproductive success by reducing infant and child mortality rates to levels observed among the Herero. These findings suggest that low !Kung fertility and mortality reflect contact with the Herero, who began expanding in large numbers into !Kung territory in the 1950s. This study emphasizes the need for a more rigorous comparative perspective in anthropology to understand better the significance of findings from restricted populations, and I suggest that evolutionary ecology would benefit from shifting some of its current focus on fertility to mortality.     

Herero households

We describe details of Herero residential units and discuss the meaning of household among Herero ranchers of northwestern Botswana and conclude that there is no single meaningful household. Rather there is a dual system of local social units. From the male perspective, a household is a hamlet with the associated herd and huts or hut clusters within it. From the female perspective, a household is a hut or hut cluster with dependent children that she maintains and manages. There have been dramatic social and economic changes in this century. Herero were destitute refugees from a genocidal war in 1904, while today they are one of the wealthiest groups in the region. They suffered from infertility before antibiotics became available around 1960, so that the TFR has changed from about 2.7 to 7.0 in the last three decades. We discuss the effects of these changes on local organization.     

Age structure and sex-biased mortality among Herero pastoralists

Details of the population pyramid of living Herero and Mbanderu of Botswana suggest that infant and childhood mortality of males has been substantially greater than that of females. Direct tests from reproductive histories show that the hazard ratio is approximately 3 to 1 in favor of female survival in infancy and 2 to 1 in childhood. This biased mortality began in about 1960 in concert with recovery from infertility. A model of asymmetric fitness benefits between siblings is weakly supported. Logistic regression shows that heterogeneity among mothers explains much of the mortality of children under 2 years of age. A direct test for heterogeneity provides strong support for the hypothesis. Field methods appropriate for anthropologists are contrasted with those that are standard in demography. Finally, a contrast between these data and those from south Asia suggests that strong sex preferences may exist without being culturally articulated. Cultural norms do not necessarily coincide with behavior.     

Premarital fertility in Namibia: trends, factors and consequences

Premarital fertility, defined as fertility before first marriage, was found to be highly prevalent in Namibia. According to data from the 1992 and 2000 DHS surveys, the proportion of premarital births was 43% for all births, and 60% for the first birth. This seemed to be primarily due to a late mean age at first marriage (26.4 years) and low levels of contraception before first marriage. Data were analysed using a variety of demographic methods, including multiple decrement life table and multivariate logistic models. Major variations were found by ethno-linguistic groups: Herero and Nama/Damara had the highest levels of premarital fertility (above 60%); Ovambo and Lozi had intermediate levels of premarital fertility (around 40%); Kavongo and San appeared to have kept a more traditional behaviour of early marriage and low levels of premarital fertility (around 20%). The largest ethno-linguistic group, the Ovambo, were in a special situation, with fast increasing age at marriage and average level of premarital fertility. Whites and mixed races also differed, with Afrikaans-speaking groups having a behaviour closer to the average, whereas other Europeans had less premarital fertility despite an average age at marriage. Ethnic differences remained stable after controlling for various socioeconomic factors, such as urbanization, level of education, wealth, access to mass media, and religion. Results are discussed in light of the population dynamics and political history of Namibia in the 20th century.     

Diseases of captive cheetahs (Acinonyx jubatus): Results of the cheetah research council pathology survey, 1989–1992

Knowledge of the diseases of cheetahs is essential to prevent and treat conditions that can modulate fertility and longevity. Toward this aim, a comprehensive pathology survey was conducted under a directive from the Cheetah Species Survival Plan. To date, 31 adult cheetahs and nine cubs from 16 zoological parks have been evaluated. Also, liver biopsies from 67 female cheetahs from 22 zoological parks were examined. Veno-occlusive disease (VOD) affected 82% of deceased cheetahs and 51% of live female cheetahs, and was the cause of death in nine cheetahs. Glomerulosclerosis and nephrosclerosis affected 84% and 39% of the population, respectively, and caused renal failure in eight cheetahs. The severity of VOD and glomerulosclerosis increased with age, and was not associated with infertility. Chronic gastritis was noted in 91% of the study population, and 95% of these cases also had spiral bacteria. Feline infectious peritonitis caused the death of two cheetahs. Male cheetahs had testicular degeneration, atrophy, and/or spermatogenic arrest, but these cheetahs also had severe systemic illness. Most females did not have reproductive tract lesions that would cause infertility, including those with parovarian cysts. Ovarian histology suggested that infertile cheetahs were not ovulating. Most cubs died from pneumonia or other systemic infections. The results of this study indicate that serious diseases are prevalent in the North American cheetahs, but these diseases do not appear to be the cause of infertility in the population. However, these diseases do limit the life span and well-being of cheetahs in captivity. Further research is needed to elucidate the causes of these diseases. © 1993 Wiley-Liss, Inc.     

Gene Conversion between the X Chromosome and the Male-Specific Region of the Y Chromosome at a Translocation Hotspot

Outside the pseudoautosomal regions, the mammalian sex chromosomes are thought to have been genetically isolated for up to 350 million years. However, in humans pathogenic XY translocations occur in XY-homologous (gametologous) regions, causing sex-reversal and infertility. Gene conversion might accompany recombination intermediates that resolve without translocation and persist in the population. We resequenced X and Y copies of a translocation hotspot adjacent to the PRKX and PRKY genes and found evidence of historical exchange between the male-specific region of the human Y and the X in patchy flanking gene-conversion tracts on both chromosomes. The rate of X-to-Y conversion (per base per generation) is four to five orders of magnitude more rapid than the rate of Y-chromosomal base-substitution mutation, and given assumptions about the recombination history of the X locus, tract lengths have an overall average length of ∼100 bp. Sequence exchange outside the pseudoautosomal regions could play a role in protecting the Y-linked copies of gametologous genes from degeneration.     

Population genetics study of the differential fertility in urban populations

In an urban population with widespread birth control practice the distribution of the number of pregnancies, births and abortions was studied in a cohort of women of completed fertility. The mean number of pregnancies per woman was 4.03 +/- 0.08 (sigma = = 2.98); the mean number of births - 1.12 +/- 0.02 (sigma = 0.77). 7.4% of women which had completed their reproductive performance had no pregnancies and 19.5% - no births. The Crow's Index of the Opportunity for Selection and its components connected with differential fertility and differential mortality were estimated. In the population under study two components of selection - selection at the prenatal stages and selection associated with infertility - are shown to be still significant. Such type of selection is exemplified by investigation of couples suffering from repeated spontaneous abortions.     

Fertility levels and trends in Arsi and Shoa regions of Central Ethiopia

Levels and trends of fertility in the Arsi and Shoa regions of Central Ethiopia are examined, using data from the 1986 Population, Health and Nutrition baseline survey of the Ministry of Health of Ethiopia. The population has high fertility. Total fertility of six children per woman in the late 1960s increased to eight children per woman in the early 1980s, then declined to seven children per woman in the mid-1980s. Urban fertility declined by a substantial amount during the 15 years before the survey while rural fertility increased during the same period. The implications of high fertility are considered.     

The effects of type of female circumcision on infertility and fertility in Sudan

This study explores the association between type of female circumcision and infertility and fertility in Sudan using the 1989-90 Demographic and Health Survey. It is hypothesized that women with either Pharaonic or Intermediate circumcision would have higher infertility and lower fertility compared with women with Sunna circumcision, and that uncircumcised women would have the lowest infertility and highest fertility of the three groups. This hypothesis, a widely held assumption, proved to be largely incorrect. Though women with Pharaonic or Intermediate circumcision did have a higher prevalence of primary infertility than uncircumcised women, women with Sunna circumcision had even lower rates of primary infertility compared with uncircumcised women. This pattern prevailed in multivariate models controlling for confounding variables, where women with Pharaonic or Intermediate circumcision had significantly higher primary infertility. Moreover, though women with Pharaonic or Intermediate circumcision also had the highest prevalence of secondary infertility, once confounding covariates were controlled in multivariate models, there was no significant difference among the three groups of women. With respect to fertility, the total fertility rate was 7.6 for women with Pharaonic or Intermediate circumcision, 8.1 for women with Sunna circumcision and 8.3 for uncircumcised women. Differences in fertility were found to be insignificant when covariates were controlled. The multivariate models were estimated using logistic regression. In conclusion, Pharaonic or Intermediate circumcision may be associated with higher primary infertility while there was no evidence suggesting that either secondary infertility or fertility was associated with a woman's circumcision status.     

LOSS OF SEX IN CLONAL POPULATIONS OF A FLOWERING PLANT,DECODON VERTICILLATUS (LYTHRACEAE)

The loss of traits that no longer increase fitness is a pervasive feature of evolution, although detailed studies of the genetic, developmental, and evolutionary factors involved are few. Most perennial plants practice both sexual and clonal reproduction, and it has been hypothesized that populations with little sexual recruitment may lose the capacity for sexual reproduction by fixing mutations that disable one or more of the many processes involved in sex. The clonal, tristylous aquatic plant, Decodon verticillatus, exhibits marked geographical variation in sexual recruitment. Populations at the northern limit of the range are usually monomorphic for style length consist of single genotypes, and produce almost no seed, due, in part, to environmental conditions that inhibit pollination, fertilization, and seed maturation. Controlled crosses in a greenhouse provided evidence for greatly reduced sexual capacity in an exclusively clonal, monomorphic population. Plants from this infertile population produced only 3–18% as many seeds per pollination as fertile populations. Observations of pollen tube growth indicated that infertility is due to severe reductions in pollen tube numbers both early after pollination and later when pollen tubes were traversing the ovary, due primarily to the inability of pistils to support normal tube growth. A three-year greenhouse experiment comparing fertility, survival, and growth of F1 progenies produced from reciprocal crosses between plants from the infertile population and those from nearby fertile populations suggested that the genetic basis for infertility is simple and may involve a single recessive mutation. In addition, the results did not reveal any association between infertility and other aspects of survival and vegetative vigor. The infertile genotype was likely fixed in the population through founder effect rather than indirect selection resulting from antagonistic pleiotropy or direct selection of advantages associated with reduced investment in sexual reproduction. A broader comparison of sexual fertility in 15 clonal, monomorphic populations and five genotypically diverse, trimorphic populations under greenhouse conditions revealed substantial infertility in all but one monomorphic population. Populations varied somewhat in the stage at which infertility was expressed, however, pollen tube growth was impaired in all populations. These results provide strong support for the hypothesis that complex traits like sex are degraded by mutation when they no longer increase fitness.     

Towards an understanding of the genetics of human male infertility: lessons from flies

It has been argued that about 4–5% of male adults suffer from infertility due to a genetic causation. From studies in the fruitfly Drosophila, there is evidence that up to 1500 recessive genes contribute to male fertility in that species. Here we suggest that the control of human male fertility is of at least comparable genetic complexity. However, because of small family size, conventional positional cloning methods for identifying human genes will have little impact on the dissection of male infertility. A critical selection of well-defined infertility phenotypes in model organisms, combined with identification of the genes involved and their orthologues in man, might reveal the genes that contribute to human male infertility.     

Mitochondria,spermatogenesis and male infertility

Mitochondria and its role in male reproduction has remained an enigma since long. Similarly, etiology of male infertility in a large percentage of individuals, mainly primary infertility, has evaded concrete conclusions. Oxidative metabolism, energy production and free radical generation are the principal biological reactions occurring inside mitochondria. In addition to the above, mitochondria participates in an important process of apoptosis. Mitochondrial causes of infertility have triggered interest because of its presence in the tail of sperm and immense need of energy for sperm motility. Several studies on mitochondria have strongly suggested its role in fertility, some of which support mitochondrial role presenting numerous hypotheses, whereas others deny its very existence as a causative factor. We have, in the present review of existing literature, covered the role of mitochondria right from spermatogenesis to male infertility.     

Genetic demographic structure of rural populations of Kyrgyzstan

The genetic demographic parameters of rural populations of Kyrgyzstan have been studied. The rural population of Kyrgyzstan has the following demographic characteristics: (1) it is demographically young (the population mean age is 25-28 years); (2) the sex ratio in reproductive age groups is unfavorable; (3) the fertility is high (5.78-7.68 pregnancies and 4.27-5.20 surviving children per woman of postreproductive age; (4) interethnic marriages are rare (1.0-5.9%), whereas consanguineous marriages are frequent (1.4-12%); (5) Crow's indices are relatively low (I(tot) = 0.24-0.29, I(m) = 0.05-0.13, I(f) = 0.14-0.22); and (6) both male and female contributions of different regions of the republic make unequal contributions to the gametic structure of the population, with the gametic structure varying from generation to generation. Demographic parameters vary in rural populations of different geographic regions and with different ethnic compositions.     

Fertility and selection in tetraploid Lolium

Selection over five generations increased the fertility (seed set) in a population of tetraploid Lolium perenne from 67.57 per cent in the second (C ₂) to 73.95 per cent in the seventh (C ₇) generation. The increased fertility is associated with a high quadrivalent frequency and a low frequency of bivalents, trivalents and univalents. The high quadrivalent frequency in the selected population was achieved partly by a slight overall increase in chiasma frequency but mainly by a redistribution of chiasmata.     

Genetic-epidemiologic study of reproductive outcomes in the Ozersk population,located in "Maiak" control area

In the population of Ozyorsk town situated in the control area of the nuclear enterprise (Production Association "Mayak") the number of pregnancies and its outcomes was studied in cohort of 2.258 women of completed fertility. The mean number of pregnancies per woman is 5.6 +/- 0.07. The mean size of family is 1.9 +/- 0.02. It was estimated that 2.7% of women had no pregnancies, 4.0% of women had no delivery till the end of their reproductive performance. 4.65% of women contributed nothing to the genofond of the next generation, i.e., they had not any children lived till their reproductive performance (20 years). The Crow Index of Opportunity for Selection and its components connected with differential fertility and differential mortality were estimated. In the population under study tow components of selection--selection at the prenatal stages (72.6%) and selection associated with infertility--are shown to be significant.     

16 Years of breed management brings substantial improvement in population genetics of the endangered Cleveland Bay Horse

The consequences of poor breed management and inbreeding can range from gradual declines in individual productivity to more serious fertility and mortality concerns. However, many small and closed groups, as well as larger unmanaged populations, are plagued by genetic regression, often due to a dearth in breeding support tools which are accessible and easy to use in supporting decision‐making. To address this, we have developed a population management tool (BCAS, Breed Conservation and Management System) based on individual relatedness assessed using pedigree‐based kinship, which offers breeding recommendations for such populations. Moreover, we demonstrate the success of this tool in 16 years of employment in a closed equine population native to the UK, most notably, the rate of inbreeding reducing from more than 3% per generation, to less than 0.5%, or that attributed to genetic drift, as assessed over the last 16 years of implementation. Furthermore, with adherence to this program, the long‐term impact of poor management has been reversed and the genetic resource within the breed has grown from an effective population size of 20 in 1994 to more than 140 in 2020. The development and availability of our BCAS for breed management and selection establish a new paradigm for the successful maintenance of genetic resources in animal populations.     

The effects of age, season and fertility status on plasma and intratesticular insulin-like growth factor I concentration in stallions

The purposes of this study were to establish the basal plasma and testicular insulin-like growth factor-I (IGF-I) values for stallions ranging in age from 6 months to 23 years and to determine if IGF-I could be used as a marker for declining fertility. Blood and testes were obtained from 28 light horse stallions and colts. Of the 28 stallions, 22 were considered fertile and were categorized by age (<2 y, 5 to 10 y, 11 to 15 y, and 16 to 23 y); 12 age-matched stallions were grouped as to fertility status (fertile, subfertile, infertile); and all 28 stallions were grouped as to season of castration (breeding season vs. non-breeding season). In colts less than 2 years of age, IGF-I concentrations in plasma and testicular extracts were higher (P < 0.01) than in the other age groups and were higher in the breeding season than in the non-breeding season (P < 0.01). No significant differences in plasma or testicular extract concentrations of IGF-I were found among fertility groups. The results of this study demonstrate that plasma and testicular IGF-I levels are high in stallions younger than 2 years of age and then decline and plateau in stallions older than 5 years of age, suggesting that IGF-I may be involved in testicular development. The results allude to a possible seasonal effect on IGF-I production. However, it is difficult to separate true seasonality and the effect of age as only those stallions less than 2 years old exhibited variation between seasons. The IGF-I does not appear to have a direct relationship with declined fertility in the stallions tested, suggesting that IGF-I may not be a reliable biomarker for the diagnosis of subfertility and infertility.     

华北棉区第三代棉铃虫的经济阈值

1980—1982、1984—1985年在河北省饶阳县的不同土壤肥力水平、不同棉花品种上进行了模拟为害和自然为害试验,旨在确定第三代棉铃虫 Heliothis armigera(Hubner)虫口密度与棉花产量之间的关系.结果表明,棉花对于第三代棉铃虫为害的补偿能力较弱.较好的土壤肥力亦不能促使棉株完全补偿三代期间的受害损失.每亩皮棉减产斤数Y与第三代百株累计卵量E₃的关系为:Y=-0.2801+0.0643E₃.根据防治的直接收益与直接代价,算出了第三代棉铃虫的经济阈值为百株累计卵量35粒,这一阈值可适用于不同肥力水平的地块.     

Genome-wide association study identifies candidate genes for male fertility traits in humans

Despite the fact that hundreds of genes are known to affect fertility in animal models, relatively little is known about genes that influence natural fertility in humans. To broadly survey genes contributing to variation in male fertility, we conducted a genome-wide association study (GWAS) of two fertility traits (family size and birth rate) in 269 married men who are members of a founder population of European descent that proscribes contraception and has large family sizes. Associations between ～250,000 autosomal SNPs and the fertility traits were examined. A total of 41 SNPs with p ≤ 1 × 10(-4) for either trait were taken forward to a validation study of 123 ethnically diverse men from Chicago who had previously undergone semen analyses. Nine (22%) of the SNPs associated with reduced fertility in the GWAS were also associated with one or more of the ten measures of reduced sperm quantity and/or function, yielding 27 associations with p values < 0.05 and seven with p values < 0.01 in the validation study. On the basis of 5,000 permutations of our data, the probabilities of observing this many or more small p values were 0.0014 and 5.6 × 10(-4), respectively. Among the nine associated loci, outstanding candidates for male fertility genes include USP8, an essential deubiquitinating enzyme that has a role in acrosome assembly; UBD and EPSTI1, which have potential roles in innate immunity; and LRRC32, which encodes a latent transforming growth factor β (TGF-β) receptor on regulatory T cells. We suggest that mutations in these genes that are more severe may account for some of the unexplained infertility (or subfertility) in the general population.     

Seasonal infertility in sows: A five year field study to analyze the relative roles of heat stress and photoperiod

The objective of this study was to analyze the relative roles of high temperature and photoperiod as environmental factors of seasonal infertility in swine. The results of five years (2003-2007) of ultrasound pregnancy diagnosis carried out in 266 indoor farms were analyzed. For all farms, the data covered the entire study period. The farms were situated in four French regions. The data of 22,773 batches and 610,117 sows were included. Seasonal infertility was defined as the relative difference between the fertility rate in ‘summer’ (inseminations in weeks 25-42) and ‘winter’ (inseminations in weeks 1-18 of the same year). In each region, two meteorological variables were defined, based on the data of a reference weather station: the number of hot days (maximum temperature ≥ 25 °C) and tropical days (maximum temperature ≥ 32 °C and minimum temperature ≥ 18 °C). The mean fertility was 85%. The median seasonal infertility was 2.8% and more than 7.1% for a quarter of farms. Seasonal infertility did not vary with areas or baseline fertility (defined for each studied farm as the average winter fertility over five years). Seasonal infertility differed with the year (p < 0.001). Seasonal infertility was significantly higher during 2003 than in the other four years, which did not differ among each other. In the four regions, 2003 was the year with the highest number of hot days and 2007 with the least. Our study strengthens the hypothesis of a prominent role of photoperiod in seasonal infertility and of an additional role of heat stress the hottest years.