Evolution, development and timing of puberty

An assessment of puberty status in adolescents from the European Upper Paleolithic

Childhood and adolescence are two life-history stages that are either unique to humans, or significantly expanded in the human life course relative to other primates. While recent studies have deepened our knowledge of childhood in the Upper Paleolithic, adolescence in this period remains understudied. Here, we use bioarchaeological maturational markers to estimate puberty status of 13 Upper Paleolithic adolescents from sites in Russia, Czechia, and Italy to 1) evaluate the feasibility of the application of bioarchaeological puberty assessment methods to Upper Paleolithic (Homo sapiens) skeletal individuals, 2) estimate the timing and tempo of puberty in Upper Paleolithic adolescents compared to other archaeological populations analyzed using the same method, and 3) characterize adolescence in the Upper Paleolithic by contextualizing the results of this puberty assessment with data on individual and population-level health, morbidity and burial practices. Our results revealed that while puberty had begun by 13.5 years of age for the majority of individuals, there was a lot of variability, with the adolescents from Arene Candide (AC1 and AC16), both aged around 16 years when they died, taking several years longer to progress through puberty than their peers. Assessing the age of menarche was challenging due to the paucity of female adolescents, but based on the available evidence, it appears to have occurred between 16 and 17 years of age. For some, full adulthood had been achieved by 17-22 years, similar to the patterns seen in modern wealthy countries and in advance of historic populations living in urbanized environments. The bioarchaeological analysis of puberty among Upper Paleolithic adolescents has important implications for the study of the emergence of adolescence within human-life histories, as well as for understanding the developmental plasticity of sexual maturation across past and present human populations.

Self-reported history of breastfeeding in relation to recalled age at menarche in the United States

Menarche is a key life history event that shapes the female reproductive trajectory and is important to the study of human biology because of the associated epidemiological and social consequences later in life. Our question is whether breastfeeding is associated with the variation in timing of menarche. Using data from a college-aged female student population from Amherst, MA, we examined whether having been breastfed was associated with age at menarche. Of the 340 female participants with information on breastfeeding during infancy, we found that women who were breastfed (n = 286) had an adjusted mean age of menarche of 12.53 years (SE 0.09), while those who were not breastfed (n = 54) had an adjusted mean age of menarche of 12.04 years (SE 0.20; p < 0.03). We propose further research that explores a finer distinction between formula-fed, mixed-fed or predominantly breastfed infants, duration of breastfeeding and age at menarche.

Far from the walking pace. Ecological and evolutionary consequences of the suboptimal locomotion speeds in non-adult humans

INTRODUCTION

Locomotion activities are part of most human daily tasks and are the basis for subsistence activities, particularly for hunter-gatherers. Therefore, differences in speed walking-related variables may have an effect, not only on the mobility of the group, but also on its composition. Some anthropometric parameters related to body length could affect walking speed-related variables and contribute to different human behaviors. However, there is currently little information on the influence of these parameters in nonadult individuals.

METHODS

Overall, 11 females and 17 male child/adolescents, 8-17 years of age, volunteered to participate in this cross-sectional study. Five different pace walking tests were performed on a treadmill to calculate the optimal locomotion speed (OLS) and U-shaped relationship between the walking energy expenditure and speed (χ2 cost of transport [CoT]) (i.e., energetic walking flexibility).

RESULTS

The mean OLS was 3.05 ± 0.13 miles per hour (mph), with no differences between sexes. Similarly, there were no sex differences in walking flexibility according to the χ2 CoT. Body height (p < .0001) and femur length (p < .001) were positively correlated with χ2 CoT; however, female child/adolescents mitigated the effect of height and femur length when walking at suboptimal speeds.

CONCLUSION

Consistent with prior observations in adults, our findings suggest that anthropometric parameters related to body stature are associated with reduced suboptimal walking flexibility in children and adolescents. Taken together, these results suggest that children and adolescents can adapt their pace to the one of taller individuals without a highly energetic penalty, but this flexibility decreases with increasing body size.

Evolutionary-developmental (evo-devo) dynamics of hominin brain size

Brain size tripled in the human lineage over four million years, but why this occurred remains uncertain. Here, to study what caused this brain expansion, I mathematically model the evolutionary and developmental (evo-devo) dynamics of hominin brain size. The model recovers (1) the evolution of brain and body sizes of seven hominin species starting from brain and body sizes of the australopithecine scale, (2) the evolution of the hominin brain-body allometry and (3) major patterns of human development and evolution. I show that the brain expansion recovered is not caused by direct selection for brain size but by its genetic correlation with developmentally late preovulatory ovarian follicles. This correlation is generated over development if individuals experience a challenging ecology and seemingly cumulative culture, among other conditions. These findings show that the evolution of exceptionally adaptive traits may not be primarily caused by selection for them but by developmental constraints that divert selection.

Age-related changes in densitometry and histomorphometry of long bone during the pubertal growth spurt in male rats

Because experimental studies to determine the developmental toxicity of exposure to various substances in children are impossible, many studies use immature male rats. This study aimed to provide normative data for longitudinal bone growth with age during the puberty in male rats. In order to evaluate long bone growth and mineralization we examined bone size and bone density by dual-energy X-ray absorptiometry, analyzed histomorphometry of the growth plate, and serum hormone levels relevant to bone growth from postnatal day (PD)20 to PD60. The length and weight of long bones increased strongly by PD40, and no further increase was observed after PD50. On the other hand, tibial growth plate height decreased sharply after PD50 along with a reduction in the number of cells and columns, which was probably responsible for the absence of further lengthening of long bones. Parameters related to bone formation such as bone area ratio, and the thickness and number of trabeculae, also increased significantly between PD40 and PD50. Furthermore, serum levels of IGF-1 peaked at PD30 and testosterone increased rapidly on and after PD40, when IGF-1 levels were going down. These changes may participate in the parallel increase in mineral acquisition, as well as lengthening of long bones. Our findings provide comprehensive data for changes in bone density, histomorphometry of long bones, and hormone levels relevant to bone growth during the growth spurt. This will be useful for planning animal toxicological studies, particularly for deciding on the appropriate age of animals to use in given experiments.

Secular trends and sociodemographic, biological, and behavioural factors associated with handgrip strength in adolescents in southern Brazil: An allometric approach

The purpose of this study was to analyse secular trend in handgrip strength (HGS) in adolescents using an allometric approach and identify the factors associated. The sample comprised 657 and 1004 adolescents (14 to 19 years) in 2007 and 2017/2018, respectively, of public schools in Florianópolis, Brazil. The dependent variable was HGS normalised to body mass and height. Covariance analysis was used to examine secular trends in HGS, and multiple linear regression was used to identify associated factors. The independent variables were sociodemographic, biological, and behavioural factors. Comparison of HGS between surveys indicated a negative secular trend in both sexes (p < 0.001). In boys, there was a positive association of HGS with age and FFM in both surveys. In 2017/18, there was a positive association with sexual maturation and a negative association with sitting time and fat percentage. In girls, FFM was positively associated with HGS in both surveys. In 2007, there were positive associations of HGS with age and vigorous physical activity, whereas, in 2017/18, negative associations were observed with economic level and sitting time. The findings of the present study show a decline in adolescent HGS. And behavioural changes appear to be contributing to declines in HGS.

A future food boom rescues the negative effects of early-life adversity on adult lifespan in a small mammal

Early-life adversity, even when transient, can have lasting effects on individual phenotypes and reduce lifespan across species. If these effects can be mitigated by a high-quality later-life environment, then differences in future resources may explain variable resilience to early-life adversity. Using data from over 1000 wild North American red squirrels, we tested the hypothesis that the costs of early-life adversity for adult lifespan could be offset by later-life food abundance. We identified six adversities that reduced juvenile survival in the first year of life, though only one-birth date-had continued independent effects on adult lifespan. We then built a weighted early-life adversity (wELA) index integrating the sum of adversities and their effect sizes. Greater weighted early-life adversity predicted shorter adult lifespans in males and females, but a naturally occurring food boom in the second year of life ameliorated this effect. Experimental food supplementation did not replicate this pattern, despite increasing lifespan, indicating that the buffering effect of a future food boom may hinge on more than an increase in available calories. Our results suggest a non-deterministic role of early-life conditions for later-life phenotype, highlighting the importance of evaluating the consequences of early-life adversity in the context of an animal's entire life course.

Fetal genetically determined birth weight plays a causal role in earlier puberty timing: evidence from human genetic studies

STUDY QUESTION

Does fetal genetically determined birth weight associate with the timing of puberty?

SUMMARY ANSWER

Lower fetal genetically determined birth weight was causally associated with an earlier onset of puberty, independent of the indirect effects of the maternal intrauterine environment.

WHAT IS KNOWN ALREADY

Previous Mendelian randomization (MR) studies have indicated a potential causal link between birth weight, childhood BMI, and the onset of puberty. However, they did not distinguish between genetic variants that have a direct impact on birth weight through the fetal genome (referred to as fetal genetic effects) and those that influence birth weight indirectly by affecting the intrauterine environment (known as maternal genetic effects). It is crucial to emphasize that previous studies were limited because they did not account for the potential bias caused by unaddressed correlations between maternal and fetal genetic effects. Additionally, the proportion of birth weight variation explained by the fetal genome is considerably larger than that of the maternal genome.

STUDY DESIGN, SIZE, DURATION

We performed two-sample MR analyses to investigate the causal effect of fetal genetically determined birth weight on puberty timing using summary data from large-scale genome-wide association studies (GWASs) in individuals of European ancestry.

PARTICIPANTS/MATERIALS, SETTING, METHODS

From the two most recent GWASs specifically centered on birth weight, which included 406 063 individuals and 423 683 individuals (63 365 trios) respectively, we identified genetic variants associated with fetal genetically determined birth weight, while adjusting for maternal genetic effects. We identified genetic variants associated with childhood BMI from an independent GWAS involving 21 309 European participants. On this basis, we employed two-sample MR techniques to examine the possible causal effects of fetal genetically determined birth weight on puberty timing using a large-scale GWAS of puberty timing (including 179 117 females of European ancestry). Furthermore, we employed advanced analytical methods, specifically MR mediation and MR-Cluster, to enhance our comprehension of the causal relationship between birth weight determined by fetal genetics and the timing of puberty. We also explored the pathways through which childhood BMI might act as a mediator in this relationship.

MAIN RESULTS AND THE ROLE OF CHANCE

In the univariable MR analysis, a one SD decrease in fetal genetically determined birth weight (∼ 418 g) was associated with a 0.16 (95% CI [0.07-0.26]) years earlier onset of puberty. The multivariable MR analysis including fetal genetically determined birth weight and childhood BMI in relation to puberty timing provided compelling evidence that birth weight had a direct influence on the timing of puberty. Lower birth weight (one SD) was associated with an earlier onset of puberty, with a difference of 0.23 (95% CI [0.05-0.42]) years. We found little evidence to support a mediating role of childhood BMI between birth weight and puberty timing (-0.07 years, 95% CI [-0.20 to 0.06]).

LIMITATIONS, REASONS FOR CAUTION

Our data came from European ancestry populations, which may restrict the generalizability of our results to other populations. Moreover, our analysis could not investigate potential non-linear relationships between birth weight and puberty timing due to limitations in genetic summary data.

WIDER IMPLICATIONS OF THE FINDINGS

Findings from this study suggested that low birth weight, determined by the fetal genome, contributes to early puberty, and offered supporting evidence to enhance comprehension of the fetal origins of disease hypothesis.

STUDY FUNDING/COMPETING INTEREST(S)

C.Z. was funded by the Sichuan Province Science and Technology Program [grant number 2021JDR0189]. J.Z. was supported by grants from the National Natural Science Foundation of China [grant number 82373588]. No other authors declare any sources of funding. The authors have no conflicts of interest.

TRIAL REGISTRATION NUMBER

N/A.

Mothers' prenatal distress accelerates adrenal pubertal development in daughters

Human life history schedules vary, partly, because of adaptive, plastic responses to early-life conditions. Little is known about how prenatal conditions relate to puberty timing. We hypothesized that fetal exposure to adversity may induce an adaptive response in offspring maturational tempo. In a longitudinal study of 253 mother-child dyads followed for 15 years, we investigated if fetal exposure to maternal psychological distress related to children's adrenarche and gonadarche schedules, assessed by maternal and child report and by dehydroepiandrosterone sulfate (DHEA-S), testosterone, and estradiol levels. We found fetal exposure to elevated maternal prenatal psychological distress predicted earlier adrenarche and higher DHEA-S levels in girls, especially first-born girls, and that associations remained after covarying indices of postnatal adversity. No associations were observed for boys or for gonadarche in girls. Adrenarche orchestrates the social-behavioral transition from juvenility to adulthood; therefore, significant findings for adrenarche, but not gonadarche, suggest that prenatal maternal distress instigates an adaptive strategy in which daughters have earlier social-behavioral maturation. The stronger effect in first-borns suggests that, in adverse conditions, it is in the mother's adaptive interest for her daughter to hasten social maturation, but not necessarily sexual maturation, because it would prolong the duration of the daughter allomothering younger siblings. We postulate a novel evolutionary framework that human mothers may calibrate the timing of first-born daughters' maturation in a way that optimizes their own reproductive success.

Is endometriosis due to evolutionary maladaptation?

Similar to diabetes and unlike many pathogen-induced diseases, endometriosis is likely a result of maladaptation to the evolutionary heritage of humans. The objective of this article is to review the literature and improve understanding of the evolutionary factors behind endometriosis, leading to more effective prevention and treatment approaches. In primates, spontaneous decidualization of the endometrium evolved to ensure optimal implantation of a limited number of early embryos, unlike many non-primates which depend on early embryos to induce decidualization and subsequent pregnancy. Spontaneous decidualization results in menstrual bleeding when embryo implantation does not occur, and endometriosis is commonly believed to be caused by retrograde menstruation. Although direct evidence is lacking, it is likely that hunter-gatherer women experienced fewer menstrual periods due to pregnancy shortly after menarche, followed by repeated pregnancies and lactation. However, the mismatch between the evolved uterine physiology and rapid societal changes has led to modern women delaying pregnancy and experiencing numerous menstrual periods, potentially increasing the incidence of endometriosis. The symptoms of endometriosis are often managed by suppressing menstruation through systemic hormonal treatments, but these may have side effects. For patients with a family history of endometriosis or in the early stages of the disease, intrauterine devices releasing progesterone locally could prevent uterine bleeding and the development of endometriosis while preserving fertility and minimizing side effects.

Immigrant generation status and its association with pubertal timing and tempo among Hispanic girls and boys

PURPOSE

In the United States, Hispanic-Latino children reach puberty earlier on average than non-Hispanic white children. Yet among U.S. Hispanic/Latino children, pubertal timing comparisons between immigrant generations have not been made, hence we examined whether pubertal timing differs by immigrant generational status, independent of BMI and acculturation measures.

METHODS

Cross-sectional data on 724 boys and 735 girls, aged 10-15 years, from the Hispanic Community Children's Health Study/Study of Latino (SOL) Youth, were used to predict the median ages of thelarche, pubarche, and menarche in girls, and pubarche and voice change in boys, using Weibull survival models, while adjusting for SOL center, BMI, and acculturation.

RESULTS

In girls, the first generation began thelarche earlier than second and third generations (median age [years] [95% confidence interval]: 7.4 [6.1, 8.8] vs. 8.5 [7.3, 9.7] and 9.1 [7.6, 10.7], respectively), but began menarche later (12.9 [12.0,137] vs. 11.8 [11.0, 12.5] and 11.6 [10.6, 12.6], respectively). Pubertal timing and tempo for boys did not differ by generational status.

CONCLUSIONS

First-generation U.S. Hispanic/Latino girls had the earliest thelarche, latest menarche and longest pubertal tempo, compared to second and third generations. Factors beyond BMI and acculturation may account for the differences in pubertal timing by generational status of U.S. Hispanic/Latino girls.

Social jetlag is associated with adverse cardiometabolic latent traits in early adolescence: an observational study

Introduction

Adolescence is marked by physiological and social changes, such as puberty, increased responsibilities and earlier school start times. This often leads to insufficient sleep on school nights and the need to compensate for lost sleep on weekends, causing a misalignment between biological and social times, which has been termed social jetlag (SJL). SJL triggers stress responses and is associated with several negative health outcomes, including higher cardiometabolic risk in adults. In adolescence, however, SJL has only been consistently related to increases in adiposity but its association with other cardiometabolic indicators are unclear.

Method

In a sample of 278 healthy early adolescents (9-15 years of age; 168 girls) we investigated: 1) whether self-reported SJL is associated (using path analyses) with a cardiometabolic status latent factor obtained by testing the best fitting model via confirmatory factor analyses from an initial set of eight indicators [body mass index (BMI), waist/height ratio, triglyceride concentration, diastolic and systolic blood pressure, glycated hemoglobin, total cholesterol/high-density lipoprotein ratio (chol/HDL), and % body fat]; and 2) whether age and/or pubertal status influence the association between SJL and cardiometabolic status.

Result

We found that, for girls, higher SJL was associated with more adverse cardiometabolic latent scores (the shared variance of BMI, waist/height ratio, chol/HDL and systolic blood pressure, which had acceptable model fit indices). However, the role of age and pubertal status in this association was unclear for both sexes.

Discussion

SJL was associated with adverse cardiometabolic latent traits beyond increases in adiposity in this observational study in early female adolescents. Because disruptions of circadian rhythms are believed to lead to dysregulated energy homeostasis and not vice-versa, our findings highlight the need for sleep interventions in adolescence to help reduce the global burden of cardiometabolic ill health, especially in girls.

The energetics of childhood: Current knowledge and insights into human variation, evolution, and health

How organisms capture and ultimately use metabolic energy-a limiting resource of life-has profound implications for understanding evolutionary legacies and current patterns of phenotypic variation, adaptation, and health. Energetics research among humans has a rich history in biological anthropology and beyond. The energetics of childhood, however, remains relatively underexplored. This shortcoming is notable given the accepted importance of childhood in the evolution of the unique human life history pattern as well as the known sensitivity of childhood development to local environments and lived experiences. In this review, I have three objectives: (1) To overview current knowledge regarding how children acquire and use energy, highlighting work among diverse human populations and pointing to recent advances and remaining areas of uncertainty; (2) To discuss key applications of this knowledge for understanding human variation, evolution, and health; (3) To recommend future avenues for research. A growing body of evidence supports a model of trade-offs and constraint in childhood energy expenditure. This model, combined with advancements on topics such as the energetics of immune activity, the brain, and the gut, provides insights into the evolution of extended human subadulthood and the nature of variation in childhood development, lifetime phenotype, and health.

Trends in incidence rates of childhood type 1 diabetes mellitus: A retrospective study in Isfahan province, Iran

AIMS/INTRODUCTION

We aimed to determine the incidence trend of childhood type 1 diabetes mellitus in Isfahan province over a period of 12 years.

MATERIALS AND METHODS

In this retrospective study, children aged <20 years at the time of type 1 diabetes mellitus diagnosis, from March 2007 to March 2019, were included. The crude and adjusted incidence rate of type 1 diabetes mellitus is calculated as the number of cases per 100,000 person-years by the period. The cumulative, age- and sex-specific incidence rates were also calculated. Age-specific incidence rates were calculated for age and sex groups.

RESULTS

A total of 1,954 (983 boys and 971 girls) cases of type 1 diabetes mellitus were identified. The mean age at diagnosis in all studied populations was 9.89 (standard deviation 4.76). There were no significant differences between the proportion of boys and girls in different years (P = 0.12) and different age groups (P = 0.19). The average annual percent change of incidence rate for the total population, for girls and boys, was 6.9%, 6.7% and 6.3% respectively. The type 1 diabetes mellitus incidence rate had a significant trend to be increased from 2007 to 2019 (P < 0.001, t = 3.6).

CONCLUSION

Our findings showed that currently our region is considered a region with a high incidence rate of type 1 diabetes mellitus. Although we have had fluctuations in the incidence rate over the 12 years, the overall trend is increasing.

The future of evolutionary medicine: sparking innovation in biomedicine and public health

Evolutionary medicine - i.e. the application of insights from evolution and ecology to biomedicine - has tremendous untapped potential to spark transformational innovation in biomedical research, clinical care and public health. Fundamentally, a systematic mapping across the full diversity of life is required to identify animal model systems for disease vulnerability, resistance, and counter-resistance that could lead to novel clinical treatments. Evolutionary dynamics should guide novel therapeutic approaches that target the development of treatment resistance in cancers (e.g., via adaptive or extinction therapy) and antimicrobial resistance (e.g., via innovations in chemistry, antimicrobial usage, and phage therapy). With respect to public health, the insight that many modern human pathologies (e.g., obesity) result from mismatches between the ecologies in which we evolved and our modern environments has important implications for disease prevention. Life-history evolution can also shed important light on patterns of disease burden, for example in reproductive health. Experience during the COVID-19 (SARS-CoV-2) pandemic has underlined the critical role of evolutionary dynamics (e.g., with respect to virulence and transmissibility) in predicting and managing this and future pandemics, and in using evolutionary principles to understand and address aspects of human behavior that impede biomedical innovation and public health (e.g., unhealthy behaviors and vaccine hesitancy). In conclusion, greater interdisciplinary collaboration is vital to systematically leverage the insight-generating power of evolutionary medicine to better understand, prevent, and treat existing and emerging threats to human, animal, and planetary health.

DHEAS and nutritional status among Sidama, Ngandu, and Aka children: Effects of cortisol and implications for adrenarche

OBJECTIVE

Adrenarche, the biological event marked by rising production of dehydroepiandrosterone and its sulfate (DHEAS), may represent a sensitive period in child development, with important implications for adolescence and beyond. Nutritional status, particularly BMI and/or adiposity, has long been hypothesized as a factor in DHEAS production but findings are inconsistent, and few studies have examined this among non-industrialized societies. In addition, cortisol has not been included in these models. We here evaluate effects of height- (HAZ), weight- (WAZ), and BMI- (BMIZ) for-age on DHEAS concentrations among Sidama agropastoralist, Ngandu horticulturalist, and Aka hunter-gatherer children.

METHODS

Heights and weights were collected from 206 children aged 2-18 years old. HAZ, WAZ, and BMIZ were calculated using CDC standards. DHEAS and cortisol assays were used to determine biomarker concentrations in hair. Generalized linear modeling was used to examine effects of nutritional status on DHEAS concentrations, as well as cortisol, controlling for age, sex, and population.

RESULTS

Despite the prevalence of low HAZ and WAZ scores, the majority (77%) of children had BMI z-scores >-2.0 SD. Nutritional status has no significant effect on DHEAS concentrations, controlling for age, sex, and population. Cortisol, however, is a significant predictor of DHEAS concentrations.

CONCLUSIONS

Our findings do not support a relationship between nutritional status and DHEAS. Instead, results suggest an important role for stress and ecology in DHEAS concentrations across childhood. Specifically, effects of environment via cortisol may be influential to patterning of DHEAS. Future work should investigate local ecological stressors and their relationship to adrenarche.

Use of male-to-female sex reversal as a welfare scoring system in the protandrous farmed gilthead sea bream (Sparus aurata)

Gilthead sea bream is a highly cultured marine fish throughout the Mediterranean area, but new and strict criteria of welfare are needed to assure that the intensification of production has no negative effects on animal farming. Most welfare indicators are specific to a given phase of the production cycle, but others such as the timing of puberty and/or sex reversal are of retrospective value. This is of particular relevance in the protandrous gilthead sea bream, in which the sex ratio is highly regulated at the nutritional level. Social and environmental factors (e.g., contaminant loads) also alter the sex ratio, but the contribution of the genetic component remains unclear. To assess this complex issue, five gilthead sea bream families representative of slow/intermediate/fast growth were grown out with control or a plant-based diet in a common garden system from early life to the completion of their sexual maturity in 3-year-old fish. The plant-based diet highly enhanced the male-to-female sex reversal. This occurred in parallel with the progressive impairment of growth performance, which was indicative of changes in nutrient requirements as the result of the different energy demands for growth and reproduction through development. The effect of a different nutritional and genetic background on the reproductive performance was also assessed by measurements of circulating levels of sex steroids during the two consecutive spawning seasons, varying plasma levels of 17β-estradiol (E₂) and 11-ketotestosterone (11-KT) with age, gender, diet, and genetic background. Principal component analysis (PCA) of 3-year-old fish displayed a gradual increase of the E₂/11-KT ratio from males to females with the improvement of nutritional/genetic background. Altogether, these results support the use of a reproductive tract scoring system for leading farmed fish toward their optimum welfare condition, contributing to improving the productivity of the current gilthead sea bream livestock.

Long-term effects of prenatal undernutrition on female rat hypothalamic KNDy neurons

The nutritional environment during development periods induces metabolic programming, leading to metabolic disorders and detrimental influences on human reproductive health. This study aimed to determine the long-term adverse effect of intrauterine malnutrition on the reproductive center kisspeptin-neurokinin B-dynorphin A (KNDy) neurons in the hypothalamic arcuate nucleus (ARC) of female offspring. Twelve pregnant rats were divided into ad-lib-fed (control, n = 6) and 50% undernutrition (UN, n = 6) groups. The UN group was restricted to 50% daily food intake of the control dams from gestation day 9 until term delivery. Differences between the two groups in terms of various maternal parameters, including body weight (BW), pregnancy duration, and litter size, as well as birth weight, puberty onset, estrous cyclicity, pulsatile luteinizing hormone (LH) secretion, and hypothalamic gene expression of offspring, were determined. Female offspring of UN dams exhibited low BW from birth to 3 weeks, whereas UN offspring showed signs of precocious puberty; hypothalamic Tac3 (a neurokinin B gene) expression was increased in prepubertal UN offspring, and the BW at the virginal opening was lower in UN offspring than that in the control group. Interestingly, the UN offspring showed significant decreases in the number of KNDy gene-expressing cells after 29 weeks of age, but the number of ARC kisspeptin-immunoreactive cells, pulsatile LH secretions, and estrous cyclicity were comparable between the groups. In conclusion, intrauterine undernutrition induced various changes in KNDy gene expression depending on the life stage. Thus, intrauterine undernutrition affected hypothalamic developmental programming in female rats.

Exploring adolescence as a key life history stage in bioarchaeology

Adolescence is a unique period in the life history of an individual. It is characterized by a myriad of changes that bioarchaeologists are only just coming to appreciate, related to sexual maturation, linear growth, immunological transformation, and emotional and cognitive development. New methods allow us to measure this age of transition through the stages of the adolescent growth, as a proxy for the physical development associated with sexual maturation (puberty). This review outlines ways bioarchaeologists may draw on research developments from the fields of human biology, evolutionary theory and neurobiology to advance a more holistic approach to the study of adolescence in the past. It considers current theoretical and analytical approaches to highlight the research potential of this critical stage of life history. This synthesis integrates the most recent research in the medical sciences concerned with body and brain development, and outlines the biological processes involved with sexual and physical maturation of the adolescent. The goal of this review is to help inform potentially rewarding areas of research that bioarchaeologists can contribute to and draw from, as well as the challenges and limitations, theoretical and methodological questions, and ways in which we can develop the study of adolescence in the discipline going forward.

Adult sex ratios: causes of variation and implications for animal and human societies

Converging lines of inquiry from across the social and biological sciences target the adult sex ratio (ASR; the proportion of males in the adult population) as a fundamental population-level determinant of behavior. The ASR, which indicates the relative number of potential mates to competitors in a population, frames the selective arena for competition, mate choice, and social interactions. Here we review a growing literature, focusing on methodological developments that sharpen knowledge of the demographic variables underlying ASR variation, experiments that enhance understanding of the consequences of ASR imbalance across societies, and phylogenetic analyses that provide novel insights into social evolution. We additionally highlight areas where research advances are expected to make accelerating contributions across the social sciences, evolutionary biology, and biodiversity conservation.

Association between height growth patterns in puberty and stature in late adolescence: A longitudinal analysis in chinese children and adolescents from 2006 to 2016

Introduction

The relationship between the characteristics of puberty growth and the stature (height and overweight and obesity) in late adolescence was not clear. We aimed to explore the effects of puberty growth patterns on the stature in late adolescence.

Methods

A total of 13,143 children from a longitudinal cohort from 2006 to 2016 in Zhongshan city of China were included. The Preece-Baines growth curve was fitted for each individual child, and the age at peak height velocity (APHV), peak height velocity (PHV), and age at take-off (TOA) were obtained from the Preece-Baines model. To compare the difference in height in late adolescence (at 18 years old) at different pubertal height growth patterns (height spurt timing, intensity, and duration), the height at baseline was matched by using the propensity score matching. The log-binomial model was applied to assess the association between the three pubertal height growth patterns (timing, intensity, and duration) and overweight and obesity status in late adolescence, controlling the urbanity and body mass index (BMI) at baseline.

Results

After matching the baseline height, boys and girls in three pubertal patterns with early timing (P < 0.01), small intensity (P < 0.01), and short duration (P < 0.01) of height spurt had the lowest final height in the late adolescence. A 16% increase and 45% increase of risk for overweight and obesity were significantly associated with the early APHV in boys and girls, respectively, relative risk (RR) in boys, 1.16(95% confidence interval, CI: 1.03-1.30), P = 0.011; RR in girls, 1.45(1.21-1.75), P < 0.001. A 21% increase and 59% increase of risk for overweight and obesity were significantly associated with small PHV in boys and girls, respectively, RR in boys, 1.21(1.07-1.36), P < 0.001; RR in girls, 1.59(1.30-1.95), P < 0.001; and an 80% increase of risk for overweight and obesity with small spurt duration in girls (RR = 1.80; 95% CI: 1.49, 2.18; P < 0.001).

Conclusion

Pubertal growth patterns, including earlier puberty onset timing, smaller puberty intensity, and shorter puberty spurt duration, had a positive association with lower height risks and higher overweight and obesity risks in late adolescence.

Social drivers of maturation age in female geladas

Female reproductive maturation is a critical life-history milestone, initiating an individual's reproductive career. Studies in social mammals have often focused on how variables related to nutrition influence maturation age in females. However, parallel investigations have identified conspicuous male-mediated effects in which female maturation is sensitive to the presence and relatedness of males. Here, we evaluated whether the more "classic" socioecological variables (i.e., maternal rank, group size) predict maturation age in wild geladas-a primate species with known male-mediated effects on maturation and a grassy diet that is not expected to generate intense female competition. Females delayed maturation in the presence of their fathers and quickly matured when unrelated, dominant males arrived. Controlling for these male effects, however, higher-ranking daughters matured at earlier ages than lower-ranking daughters, suggesting an effect of within-group contest competition. However, contrary to predictions related to within-group scramble competition, females matured earliest in larger groups. We attribute this result to either: 1) a shift to "faster" development in response to the high infant mortality risk posed by larger groups; or 2) accelerated maturation triggered by brief, unobserved male visits. While earlier ages at maturation were indeed associated with earlier ages at first birth, these benefits were occasionally offset by male takeovers, which can delay successful reproduction via spontaneous abortion. In sum, rank-related effects on reproduction can still occur even when socioecological theory would predict otherwise, and males (and the risks they pose) may prompt female maturation even outside of successful takeovers.

Growth variations with opposite clinical outcomes and the emerging role of IGF-1

Normal growth pattern variations [i.e., constitutional advancement and constitutional delay of growth and puberty (CAGP and CDGP)] are the mirror image of each other and are associated with early puberty (EP) and delayed puberty (DP), respectively. Differences between CAGP and CDGP relate not only to auxological characteristics (height, weight) but also to insulin-like growth factor-1 (IGF-1). IGF-1 levels in CAGP are above average whereas in CDGP they are below average, suggesting a role for IGF-1 in the induction of these growth patterns. Herein, we provide data suggesting that early activation of the growth hormone (GH)/IGF-1 axis induces the growth pattern of CAGP. Moreover, we suggest that IGF-1 is a decisive factor for the release of the gonadotropin-releasing hormone (GnRH) inhibition brake that occurs in prepuberty. It is therefore crucial for puberty onset.

Patterns and Determinants of the Double Burden of Malnutrition Among Adolescents: A 14-Year Follow-Up of a Birth Cohort in Rural China

OBJECTIVE

To examine the prevalence of the double burden of malnutrition and its associated factors among adolescents in rural China.

STUDY DESIGN

A birth cohort of adolescents born to women in northwestern China who participated in a double-blind, randomized, controlled trial of micronutrient supplementation during pregnancy from August 2002 to January 2006 was enrolled. Follow-up was conducted from June to December 2016.

RESULTS

A total of 2115 participants were analyzed (median age 12 years; IQR ± 1), the majority of whom were male (59.7%). The nutritional status distribution was 17.72% underweight, 8.62% overweight, 0.96% obese, and 2.58% stunted. Girls were less likely to be overweight/obese (relative risk ratio [RRR] 0.67, 95% CI 0.48-0.92) but more likely to be underweight (RRR 1.65, 95% CI 1.25-2.17) or stunted (RRR 2.26, 95% CI 1.21-4.22). Children of underweight mothers (RRR 1.63, 95% CI 1.19-2.25) with a history of small for gestational age (RRR 1.64, 95% CI 1.14-2.36) or described as being a "picky eater" (RRR 1.53, 95% CI 1.18-1.99) had a greater risk of being underweight. Children whose fathers' education was primary or below (RRR 2.25, 95% CI 1.11-4.59), with maternal height <150.1 cm (RRR 2.46, 95% CI 1.12-5.39), or who had mothers with underweight (RRR 2.80, 95% CI 1.37-5.72) had a greater likelihood of stunting. Overweight/obesity was associated with high and middle household wealth (RRR 1.62, 95% CI 1.14-2.32), mothers with overweight (RRR 1.86, 95% CI 1.25-2.78), and picky eating (RRR 0.62, 95% CI 0.46-0.84).

CONCLUSIONS

Malnutrition (undernutrition and overweight/obesity) is common in rural Chinese adolescents and is associated with perinatal, genetic, and economic conditions.

An Evolution-Based Model of Causation for Aging-Related Diseases and Intrinsic Mortality: Explanatory Properties and Implications for Healthy Aging

Aging-related diseases are the most prevalent diseases in advanced countries nowadays, accounting for a substantial proportion of mortality. We describe the explanatory properties of an evolution-based model of causation (EBMC) applicable to aging-related diseases and intrinsic mortality. The EBMC takes the sufficient and component causes model of causation as a starting point and develops it using evolutionary and statistical theories. Genetic component causes are classified as “early-onset” or “late-onset” and environmental component causes as “evolutionarily conserved” or “evolutionarily recent.” Genetic and environmental component causes are considered to occur as random events following time-to-event distributions, and sufficient causes are classified according to whether or not their time-to-event distributions are “molded” by the declining force of natural selection with increasing age. We obtain for each of these two groups different time-to-event distributions for disease incidence or intrinsic mortality asymptotically (i.e., for a large number of sufficient causes). The EBMC provides explanations for observations about aging-related diseases concerning the penetrance of genetic risk variants, the age of onset of monogenic vs. sporadic forms, the meaning of “age as a risk factor,” the relation between frequency and age of onset, and the emergence of diseases associated with the modern Western lifestyle. The EBMC also provides an explanation of the Gompertz mortality model at the fundamental level of genetic causes and involving evolutionary biology. Implications for healthy aging are examined under the scenarios of health promotion and postponed aging. Most importantly from a public health standpoint, the EBMC implies that primary prevention through changes in lifestyle and reduction of environmental exposures is paramount in promoting healthy aging.

Evaluation of the resilience of the girls with central precocious puberty treated with gonadotropin-releasing hormone analog

OBJECTIVES

The aim of this study was to evaluate the resilience of girls with central precocious puberty (CPP) during treatment with a gonadotropin-releasing hormone agonist (GnRHa) and compare these results with their healthy peers.

METHODS

The Connor-Davidson Resilience Scale (CD-RISC) is a self-report scale used to quantify resilience, which is divided into seven subgroups (hardiness, coping, flexibility, purpose, optimism, regulation of emotion and cognition (REC), and self-efficacy). Fifty-one girls with CPP receiving GnRHa treatment and 51 healthy controls were involved in the study. Anthropometric measurements were evaluated and CD-RISC was performed at least six months after the initiation of GnRHa treatment.

RESULTS

There was no statistically significant difference between the anthropometric evaluations of girls with CPP and the control group. Similarly, the total score and subgroup scores of patients with CPP and the control group showed no statistically significant difference. In the correlation analysis, there was a weak negative correlation between height and flexibility (r=-0.314 p=0.025), height SDS and flexibility (r=-0.254 p=0.092), height SDS, and purpose (r=-0.285 p=0.058). Also, there was a weak negative correlation between REC and weight (r=-0.435 p=0.003), REC and weight SDS (r=-0.461 p=0.002), REC and height (r=-0.269 p=0.077), REC and height SDS (r=-0.322 p=0.033), REC and BMI (r=-0.289 p=0.058), and REC and BMI SDS (r=-0.353 p=0.019).

CONCLUSIONS

The resilience of girls with CPP treated with GnRHa was found to be similar to their healthy peers. The early diagnosis of the disease and adequate treatment may decrease the discrepancy of somatic changes between girls with CPP and their peers, which may help them to overcome the stress of CPP and long-term treatment.

Gathering Is Not Only for Girls : No Influence of Energy Expenditure on the Onset of Sexual Division of Labor

In some small-scale societies, a sexual division of labor is common. For subadult hunter-gatherers, the onset of this division dates to middle childhood and the start of puberty; however, there is apparently no physiological explanation for this timing. The present study uses an experimental approach to evaluate possible energetic differences by sex in gathering-related activities. The energetic cost of gathering-related activities was measured in a sample of 42 subjects of both sexes aged between 8 and 14 years. Body mass and other anthropometric variables were also recorded. Our results show that the energetic differences in the simulated gathering activities depend only on body mass. Both sexes expend a similar amount of energy during locomotion activities related to gathering. Discarding the energetic factor, the sexual division of tasks may be explained as an adaptation to acquire the skills needed to undertake the complex activities required during adulthood as early as possible. Carrying out gathering activities during childhood and adolescence could be favored by the growth and development cycles of Homo sapiens. Moreover, if most of the energetic costs of gathering activities depend on body mass, the delayed growth in humans relative to other primates allows subadults to practice these tasks for longer periods, and to become better at performing them. In fact, this strategy could enable them to acquire adults' complex skills at a low energetic cost that can be easily subsidized by other members of the group.

Detecting Genetic Ancestry and Adaptation in the Taiwanese Han People

The Taiwanese people are composed of diverse indigenous populations and the Taiwanese Han. About 95% of the Taiwanese identify themselves as Taiwanese Han, but this may not be a homogeneous population because they migrated to the island from various regions of continental East Asia over a period of 400 years. Little is known about the underlying patterns of genetic ancestry, population admixture, and evolutionary adaptation in the Taiwanese Han people. Here, we analyzed the whole-genome single-nucleotide polymorphism genotyping data from 14,401 individuals of Taiwanese Han collected by the Taiwan Biobank and the whole-genome sequencing data for a subset of 772 people. We detected four major genetic ancestries with distinct geographic distributions (i.e., Northern, Southeastern, Japonic, and Island Southeast Asian ancestries) and signatures of population mixture contributing to the genomes of Taiwanese Han. We further scanned for signatures of positive natural selection that caused unusually long-range haplotypes and elevations of hitchhiked variants. As a result, we identified 16 candidate loci in which selection signals can be unambiguously localized at five single genes: CTNNA2, LRP1B, CSNK1G3, ASTN2, and NEO1. Statistical associations were examined in 16 metabolic-related traits to further elucidate the functional effects of each candidate gene. All five genes appear to have pleiotropic connections to various types of disease susceptibility and significant associations with at least one metabolic-related trait. Together, our results provide critical insights for understanding the evolutionary history and adaption of the Taiwanese Han population.

The biological sex lens on early orthopaedic treatment duration and outcomes in Class III orthodontic patients: a systematic review

BACKGROUND

Treatment outcomes for Class III orthopaedic treatment are highly unpredictable and dependent on the timing of interception, age, and biological sex.

OBJECTIVE

This systematic review aimed to assess the effects of sex dimorphism on outcomes and duration of orthopaedic treatment for Class III malocclusion in young children.

SEARCH METHODS

Unrestricted search in six electronic databases until May 2021 was conducted. Supplemented by search in resources for published, unpublished literature, and ongoing trials.

SELECTION CRITERIA

Randomized and non-randomized controlled trials reporting the use of Class III growth modification appliances, with baseline and outcome data for both sexes, were included.

DATA COLLECTION AND ANALYSIS

Study selection and data extraction were performed blindly and in duplicate by two reviewers. ROBINS-I, Cochrane Risk of Bias, and GRADE tools were used for certainty assessment.

RESULTS

A total of 2429 records were screened. Four trials fulfilled the inclusion criteria, one was a randomized clinical trial (RCT) comparing facemask and facemask with mini-screw. Two clinical trials evaluated the effects of facemask appliance, one had a control group, another was prospective non-controlled. One compared the effects of the maxillary protraction bow appliance to a no treatment control. Two of the clinical trials were appraised as low and one was appraised as high risk of bias. The overall certainty of the available evidence was assessed as moderate. There was significant clinical heterogeneity in terms of methodology, type of intervention, and the measured outcomes, precluding a meta-analysis.

CONCLUSIONS

Minimal variations in sagittal, vertical, and dentoalveolar post-treatment cephalometric changes were reported between sexes. The available evidence is unclear to support these variations. Long-term-powered RCTs assessing cephalometric outcomes between sexes until the end of growth spurt and without pooling are not available, therefore, much needed.

REGISTRATION

PROSPERO database number CRD42020185797.

Early Puberty Is Associated With Higher Academic Achievement in Boys and Girls and Partially Explains Academic Sex Differences

PURPOSE

On average, boys have lower academic achievement than girls. We investigated whether the timing of puberty is associated with academic achievement, and whether later puberty among boys contributes to the sex difference in academic achievement.

METHOD

Examination scores at age 16 were studied among 13,477 British twins participating in the population-based Twins Early Development Study. A pubertal development scale, a height-based proxy of growth spurt, and age at menarche were used as indicators of puberty. Associations between puberty, sex, and academic achievement were estimated in phenotypic mediation models and biometric twin models.

RESULTS

Earlier puberty was associated with higher academic achievement both in boys and girls. The exception was early age at menarche in girls, which associated with lower academic achievement. More than half of the sex differences in academic achievement could be linked to sex differences in pubertal development, but part of this association appeared to be rooted in prepubertal differences. The biometric twin modelling indicated that the association between puberty and academic achievement was due to shared genetic risk factors. Genetic influences on pubertal development accounted for 7%-8% of the phenotypic variation in academic achievement.

CONCLUSIONS

Pubertal maturation relates to the examination scores of boys and of girls. This can give genes related to pubertal maturation an influence on outcomes in education and beyond. Sex differences in pubertal maturation can explain parts of the sex difference in academic achievement. Grading students when they are immature may not accurately measure their academic potential.

Endocrine-Disrupting Chemicals and Early Puberty in Girls

In recent decades, pubertal onset in girls has been considered to occur at an earlier age than previously. Exposure to endocrine-disrupting chemicals (EDCs) has been associated with alterations in pubertal timing, with several reports suggesting that EDCs may have a role in the secular trend in pubertal maturation, at least in girls. However, relevant studies give inconsistent results. On the other hand, the majority of girls with idiopathic precocious or early puberty present the growth pattern of constitutional advancement of growth (CAG), i.e., growth acceleration soon after birth. Herein, we show that the growth pattern of CAG is unrelated to exposure to endocrine-disrupting chemicals and is the major determinant of precocious or early puberty. Presented data suggest that EDCs, at most, have a minor effect on the timing of pubertal onset in girls.

Faster life history strategy manifests itself by lower age at menarche, higher sexual desire, and earlier reproduction in people with worse health

Factors which indicate lower life expectancy also induce switching to a faster life strategy, that is, a higher investment in current reproduction at the expense of future reproduction and body maintenance. We tested a hypothesis according to which impairment of individual health serves as a signal for switching to a faster life strategy using online-gathered data from 32,911 subjects. Worse health was associated with lower age at menarche and earlier initiation of sexual life in women and higher sexual desire and earlier reproduction in both sexes. Individuals with worse health also exhibited lower sexual activity, lower number of sexual partners, and lower total number of children. These results suggest that impaired health shifts individuals towards a faster life strategy but also has a negative (physiological) effect on behaviours related to sexual life. Signs of a faster life strategy were also found in Rh-negative men in good health, indicating that even just genetic predisposition to worse health could serve as a signal for switching to a faster life strategy. We suggest that improved public health in developed countries and the resulting shift to a slower life strategy could be the ultimate cause of the phenomenon of demographic transition.

Influences of Differing Menarche Status on Motor Capabilities of Girls, 13 To 16 Years: A Two-Year Follow-Up Study

Puberty and the onset of menarche influences the motor performance of girls. However, the magnitude of these influences during varying maturity status, is not clear. This longitudinal study over two years aimed to investigate differences in motor fitness between early and late developing girls based on pre- and post-menarche status. A convenience sample (n = 58) of girls aged 13.51 ± 3.51, divided by means of the Status Quo method into pre (n = 13) and post-menarche (n = 45) groups, was used. Motor fitness was tested once annually by standardized protocols. Basic statistics, independent t-testing and a repeated measures ANOVA with a post hoc Bonferonni correction were used (p < 0.05 = statistical significance). Effect sizes were determined by Cohen's d-values. Only explosive upper body strength differed significantly between groups during baseline, favoring post-menarche girls. Initially, post-menarche girls showed advantages in hand-eye coordination and speed (p > 0.05) with pre-menarche girls performing better in agility and explosive leg strength (p > 0.05). At 15.51 years, no significant, between-group differences were found. Pre-menarche girls surpassed post-menarche girls in hand-eye coordination and 0-40 m speed and post-menarche girls displayed higher explosive leg and upper body strength scores (p > 0.05). Our data show that the potential to excel in sport based on motor capabilities can only be accurately estimated 1-2 years after reaching menarche.

Characterization of pubertal development of girls in rural Bangladesh

This study aimed to describe the timing and patterns of pubertal maturation of girls living in rural Bangladesh. Starting in September 2015, a total of 15,320 girls from a birth cohort, aged 9 to 15 years at initial encounter, were visited twice at about a one year interval, typically in their birth month. Participants were asked to self-report extent of pubertal maturation, including breast development, pubic hair growth and age at menarche, if applicable. Pubertal stage (abbreviated as B2 and B3-4 for breast development and PH2 and PH3-4 for pubic hair growth) was assigned. Data from both visits were pooled, yielding a total of 29,377 age-related observations per pubertal characteristic. Probit regression models were used to estimate distributions of age at which each stage of pubertal development was attained. Before age 8, <3% of the study population initiated pubertal maturation as indicated by onset of breast development (B2). The median (95% confidence interval) age of B2 and B3-4 was 11.02 (11.00–11.04) and 12.82 (12.80–12.83) years, respectively; and 12.93 (12.91–12.94) and 14.29 (14.27–14.31) years for the onset (PH2) and advanced stage (PH3-4) of pubic hair growth, respectively. Median age at menarche was 13.17 (13.15–13.19) years, with 2.15 years of timespan from B2 to menarche. Girls in rural Bangladesh progressed through puberty following a well-documented sequence of sexual maturation stages. The age at which each pubertal milestone took place was somewhat later, but the tempo from breast development to menarche was comparable to that observed elsewhere. Our findings present a current norm of pubertal maturation in a typical, rural adolescent population in South Asia, which could help inform future studies and interventions to preserve or improve early adolescent health and development.

Glucocorticoids, the evolution of the stress-response, and the primate predicament

The adrenocortical stress-response is extraordinarily conserved across mammals, birds, fish, reptiles, and amphibians, suggesting that it has been present during the hundreds of millions of years of vertebrate existence. Given that antiquity, it is relatively recent that primate social complexity has evolved to the point that, uniquely, life can be dominated by chronic psychosocial stress. This paper first reviews adrenocortical evolution during vertebrate history. This produces a consistent theme of there being an evolutionary tradeoff between the protective effects of glucocorticoids during an ongoing physical stressor, versus the adverse long-term consequences of excessive glucocorticoid secretion; how this tradeoff is resolved depends on particular life history strategies of populations, species and vertebrate taxa. This contrasts with adrenocortical evolution in socially complex primates, who mal-adaptively activate the classic vertebrate stress-response during chronic psychosocial stress. This emphasizes the rather unique and ongoing selective forces sculpting the stress-response in primates, including humans.

Maternal protein restriction impairs nutrition and ovarian histomorphometry without changing p38MAPK and PI3K-AKT-mTOR signaling in adult rat ovaries

AIMS

Because an adequate protein supply is detrimental for the maintenance of folliculogenesis and ovulation, we evaluated the impact of maternal low protein diet on nutritional parameters, estrous cycle, ovarian histomorphometry, and on the expression of metabolic and survival signaling molecules in different follicular stages.

MAIN METHODS

Twenty Wistar pregnant rats were divided into two groups: the normoprotein (NP) group, composed of animals that received 17% protein, and a low-protein (LP) group, composed of animals that received 6% protein during gestation and lactation period. After weaning, female rats were fed with standard diet until the 120-days-old.

KEY FINDINGS

LP animals showed reduced body mass index, total body weight, energy intake, feed efficiency, and visceral fat. The ovarian tissue presented vascular congestion and fat accumulation in the medulla, followed by a significant reduction in the amount of primordial and primary follicles. In addition, the number of atretic follicles was higher in LP than in NP animals. Maternal undernutrition also resulted in increased levels of estradiol (E2) and progesterone (P4) while testosterone (T) was unchanged in the offspring. Although discrete changes in p38MAPK and in PI3K-AKT-mTOR immunostaining were observed in the ovarian follicles and corpus luteum in LP, no differences were found at their protein levels.

SIGNIFICANCE

Maternal protein restriction alters estrous cycle and histomorphometry of the offspring's ovary without changing the levels of intracellular regulatory molecules in adulthood. These morphofunctional changes may alter reproductive performance in female offspring, highlighting maternal dietary conditions as an important factor for offspring reproductive health.

Changes in the Growth and Development of Adolescents in a Country in Socio-Economic Transition 1993-2013

Introduction

Changes in human growth and development depend on genetic and environmental factors. In the case of Slovenia, the environmental factors changed as a result of the period of socio-economic transition that the country underwent between 1991 and 2013. The authors used anthropometric techniques to evaluate differences in body height, proportions and sexual maturity in 1,221 adolescents aged 14 in 1993, 2003 and 2013.

Methods

Data was collected as a part of the ACDSi study, which has monitored children’s somatic growth and motor development every decade over the last 40 years.

Results

Between 1993 and 2013, a trend (p=0.08) towards increased body height was observed in males. The comparison of age at peak height velocity (PHV) between generations demonstrated a trend (p=0.07) of earlier entry into puberty in adolescents in 2013 compared to those in 1993. The leg-to-body height ratio increased (p<0.05) with every decade in males, while in females it decreased (p<0.05) in 2013. Similar trends were observed in the leg-to-trunk ratio. Contemporary generations experienced PHV at a younger age (p<0.05), which is true for both genders even in adolescents born no more than two decades (1993 (2013) apart. In both generations, females experienced PHV sooner than their male peers.

Conclusion

The authors assume that females of the 2013 generation reached puberty earlier than females of older generations. It is most likely that, unlike females from older generations and unlike males, they were already at the stage of trunk growth at the time of the measurements, which explains the observed changes in their trunk length, leg-to-body height and leg-to-trunk ratios in comparison to earlier generations.

Accelerated reproduction is not an adaptive response to early-life adversity in wild baboons

In humans and other long-lived species, harsh conditions in early life often lead to profound differences in adult life expectancy. In response, natural selection is expected to accelerate the timing and pace of reproduction in individuals who experience some forms of early-life adversity. However, the adaptive benefits of reproductive acceleration following early adversity remain untested. Here, we test a recent version of this theory, the internal predictive adaptive response (iPAR) model, by assessing whether accelerating reproduction following early-life adversity leads to higher lifetime reproductive success. We do so by leveraging 48 y of continuous, individual-based data from wild female baboons in the Amboseli ecosystem in Kenya, including prospective, longitudinal data on multiple sources of nutritional and psychosocial adversity in early life; reproductive pace; and lifetime reproductive success. We find that while early-life adversity led to dramatically shorter lifespans, individuals who experienced early adversity did not accelerate their reproduction compared with those who did not experience early adversity. Further, while accelerated reproduction predicted increased lifetime reproductive success overall, these benefits were not specific to females who experienced early-life adversity. Instead, females only benefited from reproductive acceleration if they also led long lives. Our results call into question the theory that accelerated reproduction is an adaptive response to both nutritional and psychosocial sources of early-life adversity in baboons and other long-lived species.

Thinness and fecundability: Time to pregnancy after adolescent marriage in rural Bangladesh

Undernutrition may affect fecundability, but few studies have quantified this relationship. In rural Bangladesh, where newlywed couples face strong pressures to become pregnant, we assessed fecundability, estimated by time to pregnancy (TTP), and its association with preconceptional thinness among nulligravid, newlywed female adolescents. During 2001-2002, 5,516 newlywed women aged 12-19 years participated in a home-based, 5-weekly surveillance system for 5-6 years to enrol pregnant women into an antenatal vitamin A or β-carotene supplementation trial. Thinness was defined as a left mid-upper arm circumference (MUAC) ≤21.5 versus >21.5 cm. At each visit, staff obtained a monthly history of menstruation. Report of amenorrhea prompted a human chorionic gonadotropin urine test to confirm pregnancy. We derived hazard ratios (with 95% confidence intervals [CI]) for pregnancy and Kaplan-Meier curves for TTP. Ages of women at marriage and pregnancy detection (mean ± standard deviation) were 15.3 ± 1.9 and 17.0 ± 1.9 years, respectively. A total of 82.7% of thinner and 87.3% of better nourished women became pregnant. The unadjusted and multivariable relative hazard of ever becoming pregnant was 0.84 (95% CI [0.78, 0.89]) and 0.86 (95% CI [0.81, 0.92]), respectively, and TTP was 12 weeks longer (median [95% CI]: 63 [58-68] vs. 51 [49-54]) in women whose MUAC was ≤21.5 versus >21.5 cm. In rural Bangladesh, thin adolescent newlywed girls have a lower probability of becoming pregnant and experience a longer time to pregnancy.

Adolescence and innovation in the European Upper Palaeolithic

Childhood and adolescence are two stages of development that are unique to the human life course. While childhood in the Pleistocene has received considerable attention in recent years, adolescence during the same period remains an understudied area of research. Yet it is during adolescence that key social, physical and cognitive milestones are reached. Thus, through studying adolescents, there is enormous potential for improving our understanding of Upper Palaeolithic lifeways more broadly. The reason for the dearth of these types of studies may be the perceived methodological difficulty of identifying adolescents in the archaeological record. In many ways, it is easier to distinguish children (sensu lato) from adults based on size, developmental age and associated artefacts. Adolescents, however, are often seen as more ambiguous, more liminal. Working within an evolutionary framework and using a definition of adolescence rooted in biology, we draw on psychology, ethnography and palaeodemography to develop a model of what it might have meant to be a 'teenager' in the European Upper Palaeolithic. Citing the biological, social and cognitive changes that occur during this life stage, we propose an important role of teenagers in the origins and spread of new ideas and innovations throughout the Late Pleistocene.

The levelling-off of the secular trend of age at menarche among Italian girls

OBJECTIVE

The main aim of this study was to verify whether the secular trend stopped in Italy by comparing the results of a 1990-2000 birth cohort versus a 1980-1990 birth cohort of Italian young women. The results were used to speculate about age at menarche as adaptive response to non-genetic factors.

METHODS

In 2016, a study was set on 413, 18-to-26 year-old women (1990-2000 birth cohort) attending two Italian Universities by web-based, self-reported questionnaires. Previously in 2000, a research including 3,783 high school female students (1980-1990 birth cohort) was led. The age at menarche distribution was performed by Kaplan-Meier analysis. The comparison between the findings of the two birth cohorts was performed by Wilcoxon sum-rank test. Mixed models analysis was applied to evaluate the effect of cohort and socio-economic status on age at menarche.

RESULTS

1990-2000 cohort's age at menarche median was 12.44y (95%CI 12.37; 12.59y). There was no significant difference with age at menarche of the previous cohort (p = 0.56). Consistently, the advance of age at menarche in comparison to the mothers' one was not significantly different between the two cohorts (-0.27y±0.10y vs -0.25y±0.03y, p = 0.33). The socio-economic level was not significantly associated with menarcheal age.

CONCLUSIONS

The findings of this study confirm that, like in other developed countries, the advance of age at menarche has stopped in Italy, consistently with the stop of the improvement of socio-economic conditions. Further studies are needed to explore the differential effect of each non-genetic factor to outline future scenarios of human sexual maturation.

TRIAL REGISTRATION

the Comitato Etico per la Sperimentazione Clinica (CESC) della Provincia di Padova of the Veneto Region (Italy), n°3993/U16/16.

Evolutionary life history theory as an organising framework for cohort studies: insights from the Cebu Longitudinal Health and Nutrition Survey

By tracking a group of individuals through time, cohort studies provide fundamental insights into the developmental time course and causes of health and disease. Evolutionary life history theory seeks to explain patterns of growth, development, reproduction and senescence, and inspires a range of hypotheses that are testable using the longitudinal data from cohort studies. Here we review two decades of life history theory-motivated work conducted in collaboration with the Cebu Longitudinal Health and Nutrition Survey (CLHNS), a birth cohort study that enrolled more than 3000 pregnant women in the Philippines in 1983 and has since followed these women, their offspring and grandoffspring. This work has provided evidence that reproduction carries "costs" to cellular maintenance functions, potentially speeding senescence, and revealed an unusual form of genetic plasticity in which the length of telomeres inherited across generations is influenced by reproductive timing in paternal ancestors. Men in Cebu experience hormonal and behavioural changes in conjunction with changes in relationship and fatherhood status that are consistent with predictions based upon other species that practice bi-parental care. The theoretical expectation that early life cues of mortality or environmental unpredictability will motivate a "fast" life history strategy are confirmed for behavioural components of reproductive decision making, but not for maturational tempo, while our work points to a broader capacity for early life developmental calibration of systems like immunity, reproductive biology and metabolism. Our CLHNS findings illustrate the power of life history theory as an integrative, lifecourse framework to guide longitudinal studies of human populations.

Fingerprint evidence for the division of labour and learning pottery-making at Early Bronze Age Tell eṣ-Ṣâfi/Gath, Israel

The organization of craft production has long been a marker for broader social, economic and political changes that accompanied urbanism. The identity of producers who comprised production groups, communities, or workshops is out of reach using conventional archaeological data. There has been some success using epidermal prints on artefacts to identify the age and sex of producers. However, forensic research indicates that a combination of ridge breadth and ridge density would best identify the age and sex of individuals. To this end, we combine mean ridge breadth (MRB) and mean ridge density (MRD) to distinguish the age and sex of 112 fingerprints on Early Bronze Age (EB) III pottery from the early urban neighbourhood at Tell eṣ-Ṣâfi/Gath, Israel, dating to a 100 year time span. Our analysis accounts for the shrinkage of calcareous fabrics used to make six type of vessels, applies a modified version of the Kamp et al. regression equation to the MRB for each individual print, and infers sex by correlating MRD data to appropriate modern reference populations. When the results are combined, our analyses indicate that most fingerprints were made by adult and young males and the remainder by adult and young females. Children’s prints are in evidence but only occur on handles. Multiple prints of different age and sex on the same vessels suggest they were impressed during the training of young potters. Production appears dominated by adult and young males working alone, together, and in cooperation with adult and/or young females. Vessels with prints exclusively by females of any age are rare. This male dominant cooperative labour pattern contrasts recent studies showing that adult women primarily made Neolithic figurines in Anatolia, and more females than males were making pottery prior to the rise of city-states in northern Mesopotamia.

Experiences of delayed maturation in female vocational ballet students: An interpretative phenomenological analysis

INTRODUCTION

There is a well-established bias toward late maturing females in the context of ballet, with up to 70% of professionals delayed in maturation. The timing of maturation has implications for physical and psychological outcomes which are likely to be amplified in dance. The aim of this research was to explore the role of maturity timing in adolescent dance students' experiences of vocational ballet training.

METHODS

Semi-structured interviews were carried out with 28 adolescent female dancers of differing maturity timing across three vocational ballet schools in the UK. Interpretative phenomenological analysis was employed in the analysis of data. This study comprises findings from the nine late maturing dancers within the sample.

RESULTS

Late maturing dancers perceived a number of aesthetic and functional advantages. The aesthetic advantages noted by the dancers are congruent with the well-established bias toward a later maturing physique for ballet; being 'small' and not having 'bits' is advantageous for these dancers in terms of maintaining a more pre-pubescent look and thereby conforming more easily to the expectations of the ballet world. However, dancers in this study perceived some significant drawbacks. Despite aesthetic advantages, later maturing dancers were disadvantaged by the current training system which sees them undertaking the most crucial training period during their most rapid period of growth.

CONCLUSIONS

Greater consideration of maturation is needed within training systems and further research is warranted to understand these experiences in more depth and their implications for the physical and psychological wellbeing of young people in dance.

Self-reported Health is Related to Body Height and Waist Circumference in Rural Indigenous and Urbanised Latin-American Populations

Body height is a life-history component. It involves important costs for its expression and maintenance, which may originate trade-offs on other costly components such as reproduction or immunity. Although previous evidence has supported the idea that human height could be a sexually selected trait, the explanatory mechanisms that underlie this selection are poorly understood. Despite extensive studies on the association between height and attractiveness, the role of immunity in linking this relation is scarcely studied, particularly in non-Western populations. Here, we tested whether human height is related to health measured by self-perception, and relevant nutritional and health anthropometric indicators in three Latin-American populations that widely differ in socioeconomic and ecological conditions: two urbanised populations from Bogota (Colombia) and Mexico City (Mexico), and one isolated indigenous population (Me'Phaa, Mexico). Results showed that self-reported health is best predicted by an interaction between height and waist circumference: the presumed benefits of being taller are waist-dependent, and affect taller people more than shorter individuals. If health and genetic quality cues play an important role in human mate-choice, and height and waist interact to signal health, its evolutionary consequences, including cognitive and behavioural effects, should be addressed in future research.

Prenatal anxiety, breastfeeding and child growth and puberty: linking evolutionary models with human cohort studies

Background: Stress experienced by mothers during pregnancy can have both immediate and long-term effects on child development, potentially mediated by breastfeeding.Aim: Using a UK birth cohort study, we asked how maternal stress relates to breastfeeding and consequences for growth and puberty onset.Subjects and methods: We analysed data from the Avon Longitudinal Study of Parents and Children, collected via questionnaires and clinic visits (N: 698-8,506). We used reports of prenatal anxiety, breastfeeding, early growth and age at menarche or first voice change. Confounding by maternal age, parity, smoking, education and body mass index (BMI) was considered.Results: Mothers with higher levels of reported anxiety were less likely to breastfeed (Odds ratio (OR): 0.83, 95% confidence interval (CI): 0.71, 0.97). Breastfed infants had slower growth before weaning, although growth differences were unclear thereafter. Being breastfed for more than six months was associated with later puberty onset in females (2.76 months later than non-breastfed; CI: 0.9, 4.63), although the association was attenuated by confounders and BMI (1.51 months, CI: -0.38, 3.40). No association between breastfeeding and puberty onset in males was found.Conclusion: Our studies fit results shown previously, and we consider these in light of evolutionary life history theory while discussing key challenges in such an approach.