Cessation Of Reproduction Research Articles

Diagnosis of Menopause in a Captive Sumatran Orangutan (Pongo abelii).

Humans were long thought to be the only mammal to experience menopause, the permanent cessation of reproduction followed by a long post-reproductive lifespan. More recently, evidence has been found for the existence of menopause in other long-lived mammals, including chimpanzees and gorillas. However, orangutans, which have the longest interbirth interval of any primate, have rarely been studied in this period of their lives. In this paper, we describe clinical, ultrasound, endocrine, and histological evidence consistent with a natural menopause in a captive, previously fertile, Sumatran orangutan (Pongo abelii), aged approximately 50. Consecutive serum samples showed low levels of estradiol and high levels of follicle-stimulating hormone. Transvaginal ultrasound revealed an atrophic uterus with an antero-posterior diameter of 2.36 cm, an endometrial thickness of 2 mm, and inactive ovaries. Following this female's death from a subdural hematoma, histological examination of the ovaries showed a dense stroma with corpora albicantia, in comparison to the numerous primordial follicles seen in the ovaries of a stillborn infant female orangutan. These multiple lines of evidence suggest that Sumatran orangutans can now be added to the list of mammals which undergo a true menopause, which may ensure that females' final offspring can be reared to independence.

Ecology and social behavior of the midday gerbil Meriones meridianus: Insights from long-term research in the wild and seminatural environments

The present review provides a compilation of the published data on the ecology and social behavior of midday gerbils. Both field studies and observations under semi-natural conditions provide evidence that the midday gerbil is a nocturnal, primarily granivorous rodent that lives in highly seasonal habitats. A typical feature of the midday gerbils’ spatial organization is formation of multi-male–multi-female associations (breeding colonies) in which male home ranges overlap each other and with female ranges to a great extent, while females tend to occupy exclusive home ranges. The mating system of this species can be defined as polygynandry or promiscuity; males appear to compete for access to receptive females. The social structure in the midday gerbil is primarily based on aggressive interactions between conspecifics resulting in a dominance hierarchy among males and site-dependent dominance among females, especially during the breeding season. After the cessation of reproduction, a tendency towards more pronounced gregariousness appears, and midday gerbils form wintering groups; gerbils, however, lead solitary lives within these groups. Overall, the data presented expand our understanding of socio-ecology of gerbils.

Reproductive Cessation and Post-Reproductive Lifespan in Honeybee Workers.

The post-reproductive lifespan is an evolutionary enigma because the cessation of reproduction in animals seems contrary to the maximization of Darwinian fitness. Several theories aim to explain the evolution of menopause, one of which suggests that females of a certain age receive more fitness benefits via indirect selection (kin selection) than they would directly from continuing reproduction. Post-reproductive lifespans are not very common in nature but have been described in humans, nonhuman primates, a few species of toothed whales, guppies, and in some insect societies consisting of clonal colony members, such as aphid and ant societies. Here, we provide evidence that menopause also exists in honeybee societies. Our study shows that workers with a short life expectancy (older and/or injured workers) invest fewer resources and less time in their own reproduction than workers with a long life expectancy (younger and/or uninjured workers), even if their colony is hopelessly queenless. These results are consistent with the kin selection explanation for the evolution of menopause and help us understand the net effects of relatedness and social cooperation in animals.

No sign of reproductive cessation in the old workers of a queenless ponerine ant

In many social hymenopterans, workers of different ages engage in different tasks; younger workers remain inside the nest as intranidal workers, while older workers go outside the nest as extranidal workers (i.e., age polyethism). Previous studies have shown that ovarian activity is diminished in old, extranidal workers, but it remains unclear whether workers’ reproductive ability persists for life or whether they exhibit post-reproductive lifespans. In this study, we investigated the age-dependence of worker reproductive ability in a monomorphic ponerine ant Diacamma cf. indicum. In Diacamma ants, all females in a colony have reproductive ability, but effective reproduction is limited to one or a few dominant females, and the remaining females act as sterile helpers. Using long-term laboratory rearing, we investigated whether worker reproductive ability lasts throughout a worker’s lifetime. The ages of workers were accurately tracked, and the reproductive ability of young and old workers was examined by creating several gamergate-less sub-colonies. Results showed that at least one individual in each sub-colony developed ovaries, even in the sub-colonies that solely consisted of very old workers (> 252 days old). Interestingly, in the presence of younger workers, old workers rarely showed ovarian development. Besides age, we found a positive correlation between the amount of fat (i.e., nutritional condition) and ovarian development in old workers. Our data suggest that reproductive activity of old workers is low but maintained throughout their life in Diacamma.Significance statementFemales of social animals, such as cetaceans, are known to stop reproducing before the end of their lifespan. It is suggested that the reproductive ability of ant queens does not decline and is maintained throughout their lives; however, it is unclear whether this is also true in ant workers. We maintained ant colonies for more than 500 days and then tested whether the reproductive ability of ant workers is maintained throughout their lifespan. Even in small groups composed of only very old workers (> 252 days old), at least one individual in each group always reproduced actively. Interestingly, the presence of young workers seemed to suppress the reproduction of old workers. In addition, fat content was positively associated with the individual’s reproductive potential.

Multiple ageing effects on testicular/epididymal germ cells lead to decreased male fertility in mice

In mammals, females undergo reproductive cessation with age, whereas male fertility gradually declines but persists almost throughout life. However, the detailed effects of ageing on germ cells during and after spermatogenesis, in the testis and epididymis, respectively, remain unclear. Here we comprehensively examined the in vivo male fertility and the overall organization of the testis and epididymis with age, focusing on spermatogenesis, and sperm function and fertility, in mice. We first found that in vivo male fertility decreased with age, which is independent of mating behaviors and testosterone levels. Second, overall sperm production in aged testes was decreased; about 20% of seminiferous tubules showed abnormalities such as germ cell depletion, sperm release failure, and perturbed germ cell associations, and the remaining 80% of tubules contained lower number of germ cells because of decreased proliferation of spermatogonia. Further, the spermatozoa in aged epididymides exhibited decreased total cell numbers, abnormal morphology/structure, decreased motility, and DNA damage, resulting in low fertilizing and developmental rates. We conclude that these multiple ageing effects on germ cells lead to decreased in vivo male fertility. Our present findings are useful to better understand the basic mechanism behind the ageing effect on male fertility in mammals including humans.

Chronic and intergenerational toxic effects of 1-decyl-3-methylimidazolium hexafluorophosphate on the water flea, Moina macrocopa.

With the increasing use and production of "green solvents" ionic liquids (ILs) and their known stability in the environment, the potential adverse effects of ILs have become a focus of research. In the present study, acute, chronic, and intergenerational toxic effects of an imidazolium-based ionic liquid, 1-decyl-3-methylimidazolium hexafluorophosphate ([Demim]PF6), on Moina macrocopa were investigated following the parental exposure. The results showed that [Demim]PF6 exhibited high toxicity to M. macrocopa, and the long-term exposure significantly inhibited the survivorship, development, and reproduction of the water flea. Furthermore, it is also observed that [Demim]PF6 induced toxic effects in the following generation of M. macrocopa, resulting in the complete cessation of reproduction in the first offspring generation, and the growth of the organisms was also significantly affected. These findings provided a novel insight into the intergenerational toxicity induced by ILs to crustaceans and suggested that these compounds pose potential risks to the aquatic ecosystem.

Sex-inducing effects toward planarians widely present among parasitic flatworms

Various parasitic flatworms infect vertebrates for sexual reproduction, often causing devastating diseases in their hosts. Consequently, flatworms are of great socioeconomic and biomedical importance. Although the cessation of parasitic flatworm sexual reproduction is a major target of anti-parasitic drug design, little is known regarding bioactive compounds controlling flatworm sexual maturation. Using the planarian Dugesia ryukyuensis, we observed that sex-inducing substances found in planarians are also widespread in parasitic flatworms, such as monogeneans and flukes (but not in tapeworms). Reverse-phase HPLC analysis revealed the sex-inducing substance(s) eluting around the tryptophan retention time in the fluke Calicophoron calicophorum, consistent with previous studies on the planarian Bipalium nobile, suggesting that the substance(s) is likely conserved among flatworms. Moreover, six of the 18 ovary-inducing substances identified via transcriptome and metabolome analyses are involved in purine metabolism. Our findings provide a basis for understanding and modifying the life cycles of various parasitic flatworms.

Methods of biodiagnostics in aquatic ecotoxicology

Introduction. Modern ecotoxicology for the detection, quantitative and qualitative assessment of the content of toxicants in the environment and living organisms uses the entire spectrum of chemical-analytical methods. However, methods of biodiagnostics are specific to this science. Materials and methods. The paper summarizes information on the use of modern methods of biodiagnostics in aquatic ecotoxicology: biomarking, biotesting and bioindication. Results. The main advantage of biodiagnostics over physicochemical methods of analysis is the ability to identify the biological consequences of the action of a single stress factor or their combination. At the same time, biodiagnostic methods allow fixing the additivity, antagonism and synergy of their joint action. Biomarking differs from other biodiagnostic methods in response time from several minutes to several days, high sensitivity and sufficient specificity, since it gives the ability to register the changes occurring in the biological system at the early stages of the action of factors at their low intensity and at the same time identify the nature of the stress factor. Biotesting has a slower response time than biomarking (from several hours to several weeks), but the ecological significance at the level of an individual is more obvious: the death of an organism, a decrease in reproductive ability up to the cessation of reproduction, disruption of growth, development, various types of behavior, etc. Bioindication is characterized by a sufficiently long-time delay of responses of supraorganismal biosystems to the action of a stress factor from several weeks to several years. At the same time, it makes possible assess more adequately and reliably the changes that have occurred over a long period of timeof stress factor action in order to predict options for the further development of ecosystems. Limitations. Methods of biodiagnostics in aquatic ecotoxicology have no restrictions on their use. However, unlike the methods of physicochemical analysis, they do not allow a quantitative, and sometimes a qualitative assessment of the stress factor. Therefore, they should be used in conjunction with the methods of qualitative and quantitative physicochemical analysis. Conclusion. Thus, the biodiagnostic approach, including biomarking, biotesting, and bioindication, together with physics and chemicals analysis plays an important role in the modern integrated system for assessing the ecological state of water bodies and anthropogenic impact on them.

Oocyte mitophagy is critical for extended reproductive longevity.

Women's reproductive cessation is the earliest sign of human aging and is caused by decreasing oocyte quality. Similarly, C. elegans' reproduction declines in mid-adulthood and is caused by oocyte quality decline. Aberrant mitochondrial morphology is a hallmark of age-related dysfunction, but the role of mitochondrial morphology and dynamics in reproductive aging is unclear. We examined the requirements for mitochondrial fusion and fission in oocytes of both wild-type worms and the long-lived, long-reproducing insulin-like receptor mutant daf-2. We find that normal reproduction requires both fusion and fission, but that daf-2 mutants utilize a shift towards fission, but not fusion, to extend their reproductive span and oocyte health. daf-2 mutant oocytes' mitochondria are punctate (fissioned) and this morphology is primed for mitophagy, as loss of the mitophagy regulator PINK-1 shortens daf-2's reproductive span. daf-2 mutants maintain oocyte mitochondria quality with age at least in part through a shift toward punctate mitochondrial morphology and subsequent mitophagy. Supporting this model, Urolithin A, a metabolite that promotes mitophagy, extends reproductive span in wild-type mothers-even in mid-reproduction-by maintaining youthful oocytes with age. Our data suggest that promotion of mitophagy may be an effective strategy to maintain oocyte health with age.

Degenerative joint changes of the thoracic spine with respect to sex and age

The thoracic spine manifests degenerative changes from aging, obesity, repetitive strain and occupational stress, although sex differences are poorly understood. In this work we examine whether differences in the expression of thoracic degenerative joint changes can be found in females and males with respect to age. The two age groups included in the study are older adults between 50 and 55 years and elderly individuals between 70-75 years from the William M. Bass osteological collection of the University of Tennessee, Knoxville (USA). The first interval represents the onset of skeletal decline.The second is correlated with reduced mobility and an increase in arthritic pain. The thoracic vertebrae from 99 individuals (52 females and 47 males) were macroscopically examined on superior and inferior centra and zygapophyses for lipping, porosity and eburnation following Buikstra and Ubelaker’s (1994) scoring system. Elderly females and males exhibit a higher severity of degenerative changes than older adults, and in males the degree of lipping was extreme. Regarding older adults, males present a greater severity of lipping, extent of lipping, porosity, and extent of porosity than females. However, females show a greater degree of eburnation among older adults, particularly in the lower thoracic vertebrae. When elderly adults are compared, males express a higher degree of lipping, extent of lipping and extent of porosity than females. Like their older adult counterparts, elderly females show evidence of a greater severity in eburnation than males, suggesting hormonal profile disruption associated with reproductive cessation as well as occupational stress, may also cause the deterioration of the intervertebral discs, particularly in the lower thoracic skeleton.

How evolutionary biology can explain why human and a few marine mammal females are the only ones that are menopausal

Two fundamental questions related to menopause that have not been answered are: (1) why does menopause even occur? And, (2) of the more than six thousand known mammals extant today, why human and four whale females are the only ones that are menopausal? Answers to both of these basic questions are provided here on the basis of evolutionary biology. From observational data, it was found that there are three elemental criteria that all menopausal species must fulfill: first, it has to be long-lived (average female lifespan of the species has to be forty years or more); second, it must live in groups; and third, the average female-male lifespan differential has to be at least thirty percent or more. In addition, a corollary criterion for menopause was also established: for a species’ females to be menopausal, the Encephalization Quotient (EQ) for the species has to be 2.5 or more. Though humans do not fulfill the third menopausal criterion currently, it has been shown that when the menopausal mechanism first became common in human ancestors, in all likelihood, that principle was conformed to. Of the multitude of mammals around, only a few species satisfy all three menopausal criteria, and hence are the only ones whose females undergo the menopausal process. Many hitherto unanswered questions with respect to menopause, such as, while long and short-finned pilot whales are close to each other both genetically and physiologically, why short-finned females are menopausal while long-finned females are not, why orca females are menopausal while elephant females are not, in spite of both being long-lived, etc., can be answered on the basis of those three criteria. Why there was no selection pressure for males to undergo advanced-age reproductive cessation in those few menopausal species and why the majority of divorces occur in mid-life (40-to-60s) are also explained from a menopausal perspective.

Awareness Regarding Maternal Health Services And Birth Spacing Among The Post-Natal Mothers At A Tertiary Care Hospital, Bangalore: A Cross-Sectional Study

Background In developing nations majority of family planning programmes promote post-adolescent marriage optimal spacing and reproductive cessation at 30-34 years of age all of which result in smaller family size patterns. Such a practice would not only increase likelihood that parents would meet their parenting responsibilities but it would also have a significant influence on lowering maternal and newborn mortality. In general when maternal age drops below 20 or increases above 30 many obstetrical complications can occur during the pregnancy which is the risk factor leading to poor maternal and perinatal outcomes. With increasing parity and advanced maternal age there is an increased risk of stillbirths neonatal and post-neonatal mortality.Objective To assess knowledge and awareness regarding maternal health MCH services and postpartum family planning and birth spacing among post-natal mothers.Methodology A cross-sectional study was conducted from April to May 2022 among post-natal mothers admitted in post-natal wards inborn wards Kangaroo mother care KMC and post-partum care units in Vanivilas Hospital BMCRI Bangalore. A sample size of 131 was c based on the parent study by Pranita Achyut et al. A pre-tested semi-structured validated questionnaire was used for face-to-face interview method. Data collected was entered in Microsoft Excel and analyzed using SPSS version 21.0.Results It was observed that 52.9 of women were in the 21 to 25 years age group belonging to urban areas 59.4 from the middle class 49.6 with high school education 47.3. Association between the place of living with education p0.026 an association of education with maternal and child health services p0.024 and birth spacing p0.0001 were found to be statistically significant.Conclusion In this study most of the women were aware of maternal services in general but there was a lack of comprehensive knowledge of the services. According to this study mothers utilization of maternal health care was significantly influenced by their age level of education and parity. There are still women with misconceptions about the adverse effects associated with contraceptives and spacing methods thus its important to emphasize the awareness regarding the methods available and the need for birth spacing.

Reproductive aging and menopause-like transition in the menstruating spiny mouse (Acomys cahirinus).

Does the naturally menstruating spiny mouse go through menopause? Our study is the first to show a natural and gradual menopausal transition in a rodent. Age-related depletion of the human ovarian reserve (OvR) leads to menopause, the permanent cessation of menstruation and reproduction. Current rodent models of menopause are inappropriate for inferences of the human condition, as reproductive senescence is abrupt or induced through ovariectomy. The spiny mouse is the only confirmed rodent with a naturally occurring menstrual cycle. Histological assessment of virgin spiny mice occurred in females aged 6 months (n = 14), 1 year (n = 7), 2 years (n = 13), 3 years (n = 9) and 4 years (n = 9). Endocrinology was assessed in a further 9 females per age group. Five animals per group were used for ovarian stereology with additional ovaries collected at prenatal Day 35 (n = 3), day of birth (n = 5), postnatal Days 35 (n = 5) and 100 (n = 5) and 15 months (n = 5). Morphological changes in the reproductive system were examined using hematoxylin and eosin stains. Proliferating cell nuclear antigen immunohistochemistry assessed endometrial proliferation and sex steroids estradiol and testosterone were assayed using commercial ELISA kits. The proportion of females actively cycling was 86% at 6 months, 71% at 1 year, 69% at 2 years, 56% at 3 years and 44% at 4 years. Uterine and ovarian weights declined steadily from 1 year in all groups and corresponded with loss of uterine proliferation (P < 0.01). Estradiol was significantly decreased at 1 and 2 years compared to 6-month-old females, before becoming erratic at 3 and 4 years, with no changes in testosterone across any age. Fully formed primordial follicles were observed in prenatal ovaries. Aging impacted on both OvR and growing follicle numbers (P < 0.001-0.0001). After the age of 3 years, the follicle decline rate increased more than 5-fold. N/A. This is a descriptive study in a novel research rodent whereby reagents validated for use in the spiny mouse were limited. The gradual, rather than sudden, menopausal transition suggests that the spiny mouse is a more appropriate perimenopausal model than the current rodent models in which to examine the neuroendocrine pathways that encompass all hormonal interactions in the hypothalamic-pituitary-gonadal axis. The logistic, ethical and economic advantages of such a model may reduce our reliance on primates in menopause research and enable more thorough and invasive investigation than is possible in humans. Hudson Institute is supported by the Victorian State Government Operational Infrastructure Scheme. The authors declare no competing interests.

The Interrelationship Between Female Reproductive Aging and Survival.

The link between survival and reproductive function is demonstrated across many species and is under both long-term evolutionary pressures and short-term environmental pressures. Loss of reproductive function is common in mammals and is strongly correlated with increased rates of disease in both males and females. However, the reproduction-associated change in disease rates is more abrupt and more severe in women, who benefit from a significant health advantage over men until the age of menopause. Young women with early ovarian failure also suffer from increased disease risks, further supporting the role of ovarian function in female health. Contemporary experiments where the influence of young ovarian tissue has been restored in postreproductive-aged females with surgical manipulation were found to increase survival significantly. In these experiments, young, intact ovaries were used to replace the aged ovaries of females that had already reached reproductive cessation. As has been seen previously in primitive species, when the young mammalian ovaries were depleted of germ cells prior to transplantation to the postreproductive female, survival was increased even further than with germ cell-containing young ovaries. Thus, extending reproductive potential significantly increases survival and appears to be germ cell and ovarian hormone-independent. The current review will discuss historical and contemporary observations and theories that support the link between reproduction and survival and provide hope for future clinical applications to decrease menopause-associated increases in disease risks.

Juvenile hormone regulates photoperiod-mediated male reproductive diapause via the methoprene-tolerant gene in the ladybeetle Harmonia axyridis.

Juvenile hormone (JH) absence induces photoperiod-mediated reproductive diapause, which is characterized by reproductive cessation. Although the role of methoprene-tolerant (Met)-mediated JH signaling in photoperiod-mediated female reproduction has been well documented, its role in male reproduction remains unclear. In this study, we investigated the role of JH in regulating photoperiod-mediated development of the male internal reproductive system (IRS) in the predatory ladybeetle Harmonia axyridis (Pallas). In a previous study, we found that adult male H. axyridis reared under either a short-day (SD) or long-day (LD) photoperiod had obvious differences in IRS development, but we were unable to identify the regulators of male reproductive diapause. In this study, we found that beetles reared under an SD photoperiod had significantly lower JH titer and a relatively undeveloped male IRS compared with those reared under an LD photoperiod. Additionally, application of the JH analog (JHA) methoprene promoted IRS development. Furthermore, Met knockdown strongly blocked JH signaling in males reared under the LD photoperiod, thereby slowing IRS development. Moreover, exogenous JHA did not reverse the suppressed development of the male IRS caused by Met knockdown. These results indicate that photoperiod regulates male IRS development in H. axyridis through a conserved Met-dependent JH signaling pathway.

A Discourse on Why only Human and a Few Marine Mammal Females Are Menopausal

A fundamental question, relating to menopause that has not been convincingly answered, is this: of the thousands of known mammals on earth, why are humans and a few marine mammals the only ones whose females are menopausal? Here we provide an answer to that key question by looking at three elemental criteria that all menopausal species must fulfill: first, it has to be long-lived (average female lifespan has to be over forty years); second, it has to be a social animal, that is, it must live in groups; and third, the average female-male lifespan differential has to be at least thirty percent or more. In addition, we also found a corollary criterion for menopause: for a species’ females to be menopausal, the Encephalization Quotient (EQ) for the species has to be 2.5 or more. Though humans do not fulfill the third menopausal criterion currently, we have shown that when the menopause phenotype first became common in human ancestors, in all likelihood, that principle was conformed to. Of the multitude of mammals around, only a few species satisfy all three menopausal criteria, and hence are the only ones whose females undergo the menopause phenomenon. Many hitherto unanswered questions with respect to menopause, such as, while long and short-finned pilot whales are close to each other both genetically and physiologically, why are short-finned females menopausal while long-finned females are not, why orca females are menopausal while elephant females are not, in spite of both being long-lived, etc., can be answered on the basis of those three criteria. It is also shown that grand-mothering and mate-choice are consequences of menopause and not its cause – those mechanisms had been the explanatory bases of some previously-advanced theories trying to explain why menopause occurs in the first place. It is also shown why there was no selection pressure for males to undergo advanced-age reproductive cessation in those few menopausal species. Lastly, why the majority of divorces occur in mid-life (40s-to-60s) is explained from a menopausal perspective.

Size and survival of two freshwater snail species in relation to shedding of cercariae of castrating Echinostoma spp.

Trematode-induced castration of snails is widespread and can lead to other life history changes of snails such as changes in trajectories of size and growth or survival. The changes produced likely depend on whether the parasite or host controls allocation of host resources remaining after partial or complete cessation of host current reproduction by castrating trematodes. Documenting host life history changes, like changes in host size in response to castration, is a first step in assessing whether these changes are beneficial to the parasite (increasing transmission success) or to the host (outliving the infection) or to neither. Herein, we test for differences in size and survival among individuals of two snail species in relation to infection by Echinostoma spp. trematodes. Active shedding of Echinostoma spp. was associated with castration of all Stagnicola elodes snails from a site in Eastern Ontario. Snails actively shedding cercariae were not different in size from non-shedding, egg-laying snails but had a higher mortality than egg-laying snails. Active shedding of Echinostoma spp. cercariae was also associated with castration of nearly all Helisoma trivolvis monitored, from a site in Southwestern Ontario. Actively shedding, non-laying H. trivolvis hosts were smaller on average than non-shedding egg-laying hosts, but both non-laying and egg-laying snails survived equally well. We discuss these results in light of what is known about effects of castration on snail hosts in terms of growth and survival for these and other trematode species and speculate on whether changes in size or survival benefits parasite or host.

Role of cell cycling and polyploidy in placental trophoblast of different mammalian species.

The trophoblast cells that take part in placenta formation are characterized by different modes of multiplication of their genome that largely designates their eu- or aneuploidy level. The two main ways of genome multiplication are described in different degree: (a) endoreduplication that involves almost complete shutdown of mitosis and (b) reduced mitosis ('endomitosis') in which, by contrast, entry into mitosis and the passage of its initial stages is a prerequisite of genome multiplication. Endoreduplication observed in the trophoblast giant cells (TGC) in a range of mammalian species implies uncoupling of DNA replication from mitosis achieved by reduction of mitotic Cdk activity. The key role in the regulation of endoreduplication and endomitosis play activity of APC/C complex, geminin and E2F family. A programme of genome multiplication and cell cycle progression may include depolyploidization achieved by specific mitotic or non-mitotic (amitotic) division of the giant nucleus. In some mammalian species (Rodents), this process represents the final step of the giant cell lifespan that coincides with complete cessation of cell or genome reproduction. Meantime, in other species the process may take part in cell reproduction during lengthy pregnancy. The dynamics of fox and human polyploidization is similar by the possibility of a simultaneous increase in the proportion of endopolyploid and low-polyploid cells. Reduced mitoses, endoreduplication and depolyploidization appear to be an evolution strategy allowing to generate the functionally different trophoblast cell populations depending of the lifestyle of life of the animal species. Some placental pathologies may be accounted for disturbance of the programme of the cell/genome reproduction of the giant and low-ploid cell populations.

The optimal timing of teaching and learning across the life course.

The evolutionary biologist W. D. Hamilton (Hamilton 1966 J. Theor. Biol.12, 12-45. (doi:10.1016/0022-5193(66)90184-6)) famously showed that the force of natural selection declines with age, and reaches zero by the age of reproductive cessation. However, in social species, the transfer of fitness-enhancing resources by postreproductive adults increases the value of survival to late ages. While most research has focused on intergenerational food transfers in social animals, here we consider the potential fitness benefits of information transfer, and investigate the ecological contexts where pedagogy is likely to occur. Although the evolution of teaching is an important topic in behavioural biology and in studies of human cultural evolution, few formal models of teaching exist. Here, we present a modelling framework for predicting the timing of both information transfer and learning across the life course, and find that under a broad range of conditions, optimal patterns of information transfer in a skills-intensive ecology often involve postreproductive aged teachers. We explore several implications among human subsistence populations, evaluating the cost of hunting pedagogy and the relationship between activity skill complexity and the timing of pedagogy for several subsistence activities. Long lifespan and extended juvenility that characterize the human life history likely evolved in the context of a skills-intensive ecological niche with multi-stage pedagogy and multigenerational cooperation. This article is part of the theme issue 'Life history and learning: how childhood, caregiving and old age shape cognition and culture in humans and other animals'.

Невидимый дизонтогенез поколений X, Y, Z (трансформация черт социальной субъектности)

The article analyzes the causes of population dysontogenesis-a hidden process of loss of human subjectivity: the destruction of its psychophysiological and psychosocial qualities necessary for the normal activity of society. Violations caused by unformed structures of the child’s brain during the period of socialization in the family and school are hardly noticeable in a state of comfort, but they manifest themselves under normative and especially peak psychophysiological loads: deviant behaviors, educational failure, deterioration of health and loss of reproductive functions. The consolidation of dysontogenesis in generations X, Y, and Z occurs through international educational standards that simplify educational programs and reduce didactic requirements to a level beyond which pathophenomenes become barely noticeable, but continue to accumulate statistically at the lower limit of the norm. Compensation for impaired functions occurs at the expense of modern means of digital communication-there is a non-specific “swarm” subjectivity: emotionally unstable, easily suggestible representatives of generations Y and Z become the main resource base of extremist and terrorist organizations. The loss of basic social functions of goal-setting and control, empathy and passionarity in generations X, Y, Z, a simplified view of reality, increased lability and network conformism, decreased libido, and redirection of creative energy to the virtual-all this leads to the cessation of reproduction of the properties of society as a system structure. Restoration of systemogenetic development is possible only if the basic functions of the social state — science, education and upbringing-are provided.