Early menarche as an alternative reproductive tactic in human females: an evolutionary approach to reproductive health issues

Associations of maternal anthropometrics with newborn anogenital distance and the 2:4 digit ratio

STUDY QUESTION

Are maternal anthropometrics associated with anogenital distance (AGD) and 2:4 digit ratio (2:4D) in newborns?

SUMMARY ANSWER

Select maternal anthropometrics indicative of obesity or increased adiposity are associated with elongated AGD in daughters.

WHAT IS KNOWN ALREADY

Excessive maternal weight or adiposity before or in early pregnancy may impact child reproductive, and other hormonally mediated, development. AGD and 2:4D are proposed markers of in utero reproductive development.

STUDY DESIGN, SIZE, DURATION

This study includes 450 mother/newborn dyads participating in the Illinois Kids Development Study (I-KIDS), a prospective pregnancy cohort from Champaign-Urbana, IL, USA. Participants included in the current study enrolled between 2013 and 2018.

PARTICIPANTS/MATERIALS, SETTING, METHODS

Most mothers in this study were college-educated (82%) and non-Hispanic White (80%), and 55% were under- or normal weight before pregnancy. Pregnant women aged 18-40 years reported pre-pregnancy weight and height to calculate pre-pregnancy BMI. At 8-15 weeks gestation, we measured waist and hip circumference, and evaluated weight, % body fat, visceral fat level, % muscle and BMI using bioelectrical impedance analysis. Within 24 h of birth, we measured newborn 2nd and 4th left/right digits to calculate the 2:4D. In daughters, we measured AGDAF (anus to fourchette) and AGDAC (anus to clitoris). In sons, we measured AGDAS (anus to scrotum) and AGDAP (anus to base of the penis).

MAIN RESULTS AND THE ROLE OF CHANCE

Select maternal anthropometrics were positively associated with AGD in newborn daughters, but not sons. For example, AGDAC was 0.73 mm (95% CI: 0.15, 1.32) longer for every interquartile range (IQR) increase in pre-pregnancy BMI and 0.88 mm (95% CI: 0.18, 1.58) longer for every IQR increase in hip circumference, whereas AGDAF was 0.51 mm (95% CI: 0.03, 1.00) and 0.56 mm (95% CI: 0.03, 1.09) longer for every IQR increase in hip and waist circumference, respectively. Quartile analyses generally supported linear associations, but additional strong associations emerged in Q4 (versus Q1) of maternal % body fat and visceral fat levels with AGDAC. In quartile analyses, we observed only a few modest associations of maternal anthropometrics with 2:4D, which differed by hand (left versus right) and newborn sex. Although there is always the possibility of spurious findings, the associations for both measures of female AGD were consistent across multiple maternal anthropometric measures, which strengthens our conclusions.

LIMITATIONS, REASONS FOR CAUTION

Our study sample was racially and ethnically homogenous, educated and relatively healthy, so our study may not be generalizable to other populations. Additionally, we may not have been powered to identify some sex-specific associations, especially for 2:4D.

WIDER IMPLICATIONS OF THE FINDINGS

Increased maternal weight and adiposity before and in early pregnancy may lengthen the female AGD, which warrants further investigation.

STUDY FUNDING/COMPETING INTEREST(S)

This publication was made possible by the National Institute for Environmental Health Sciences (NIH/NIEHS) grants ES024795 and ES022848, the National Institute of Child Health and Human Development grant R03HD100775, the U.S. Environmental Protection Agency grant RD83543401 and National Institute of Health Office of the Director grant OD023272. Its contents are solely the responsibility of the grantee and do not necessarily represent the official views of the US EPA or NIH. Furthermore, the US EPA does not endorse the purchase of any commercial products or services mentioned in the publication. This project was also supported by the USDA National Institute of Food and Agriculture and Michigan AgBioResearch. The authors declare no competing interests.

TRIAL REGISTRATION NUMBER

N/A.

Association of early menarche with elevated BMI, lower body height and relative leg length among 14- to 16-year-old post-menarcheal girls from a Maya community in Yucatan, Mexico

Human body segments have different timing and tempo of growth. Early menarche (EM) as an indicator of early reproductive maturity results in a shortened height and leg length. Relatively larger trunk may increase risk for more body fat deposit and higher body mass index (BMI) due to the allometry of total body fat with body proportions. The objective of the study was to assess the association of EM with BMI, absolute body size [height, sitting height (SH), subischial leg length (SLL)] and relative body dimensions [sitting height to subischial leg length ratio (SHSLLR), relative subischial leg length (RSLL)] among 14- to 16-year-old post-menarcheal girls from a rural Maya community in Quintana Roo, Yucatan, Mexico. In a cross-sectional study, post-menarcheal girls (n=51) aged 14 to 16 years had EM (n=22) (<12 years of age) and not early menarche (NEM, n=29). Anthropometric measurements of height, weight, and SH were recorded. Derived variables were BMI, height and BMI-for-age z-scores, SLL, SHSLLR, and RSLL. Mean value of age at menarche (AM) was 13 years (EM 11 years, NEM 14 years). Mean values of height (EM 159 cm, NEM 164 cm), BMI (EM 20 kg/m2, NEM 19 kg/m2), sitting height (EM 81 cm, NEM 78 cm), SLL (EM 79 cm, NEM 85 cm), SHSLLR (EM 102.93%, NEM 92.03%), and RSLL (EM 49%, NEM 52%) were different (p<0.05) in the two groups. BMI showed significant negative correlation with AM (Pearson’s r=-0.29, p<0.04). Linear regression models adjusted for age showed that EM had different interrelationships (p<0.05) with body dimensions: positive with BMI, SH, SHSLLR, and negative with height, SLL, and RSLL. Earlier AM was associated with higher BMI, SH, SHSLLR and lower SLL, RSLL, explaining lower body height and leg length among the participant EM girls. In the light of life history theory, EM results in a growth trade-off, short stature and larger trunk relative to leg length that might enhance risk for body fat gain.

Severe deprivation in early childhood leads to permanent growth stunting: Longitudinal analysis of height trajectories from childhood-to-adulthood

BACKGROUND

Childhood institutional deprivation is associated with growth stunting in childhood but long-term effects in adulthood remain uncertain.

OBJECTIVE

To examine the impact of global institutional deprivation experienced in early childhood on subsequent growth with a special focus on final adult height and puberty timing.

PARTICIPANTS & SETTING

The study was originally set in the UK, though some adoptive families lived abroad by the time of the adult follow up. 165 individuals adopted by UK families before 43 months of age from Romanian orphanages after the fall of the Ceaușescu regime in the early 1990's were compared to 51 non-deprived UK adoptees, adopted before the age of 6 months.

METHODS

The English and Romanian Adoptees (ERA) study is a 20-year longitudinal natural experiment on the effects of institutional deprivation on development. Key growth milestones were extracted from growth curve modelling of height data collected at ages 4, 6, 11, 15 and 23 years using a Bayesian approach to fit the JPA2 model.

RESULTS

Deprivation effects on height were present at the take-off point of accelerating adolescent growth and persisted into adulthood - the largest effects being for individuals who experienced over six months of deprivation. Deprivation was associated with earlier take-off and achievement of peak height velocity of adolescent growth acceleration - an effect driven largely by females' data and correlated with parent ratings of pubertal development.

CONCLUSIONS

Early deprivation appears to reset tempo of growth early in development leading to permanent growth stunting in adulthood and accelerated onset of puberty, specifically in females.

Hormones and human developmental plasticity

Natural selection favors the evolution of mechanisms that optimize the allocation of resources and time among competing traits. Hormones mediate developmental plasticity, the changes in the phenotype that occur during ontogeny. Despite their highly conserved functions, the flexibilities of human hormonal systems suggest a strong history of adaptation to variable environments. Physiological research on developmental plasticity has focused on the early programming effects of stress, the hypothalamus-pituitary-adrenal axis (HPAA) and the hypothalamus-pituitary-gonadal axis (HPGA) during critical periods, when the hormones produced have the strongest influence on the developing brain. Often this research emphasizes the maladaptive effects of early stressful experiences. Here we posit that the HPAA and HPAG systems in human developmental plasticity have evolved to be responsive to complex and dynamic problems associated with human sociality. The lengthy period of human offspring dependency, and its associated brain development and risks, is linked to the uniquely human combination of stable breeding bonds, extensive paternal effort in a multi-male group, extended bilateral kin recognition, grandparenting, and controlled exchange of mates among kin groups. We evaluate an evolutionary framework that integrates proximate physiological explanations with ontogeny, phylogeny, adaptive function, and comparative life history data.

Changes in Biological Pathways During 6,000 Years of Civilization in Europe

The beginning of civilization was a turning point in human evolution. With increasing separation from the natural environment, mankind stimulated new adaptive reactions in response to new environmental factors. In this paper, we describe direct signs of these reactions in the European population during the past 6,000 years. By comparing whole-genome data between Late Neolithic/Bronze Age individuals and modern Europeans, we revealed biological pathways that are significantly differently enriched in nonsynonymous single nucleotide polymorphisms in these two groups and which therefore could be shaped by cultural practices during the past six millennia. They include metabolic transformations, immune response, signal transduction, physical activity, sensory perception, reproduction, and cognitive functions. We demonstrated that these processes were influenced by different types of natural selection. We believe that our study opens new perspectives for more detailed investigations about when and how civilization has been modifying human genomes.

Skeletal age estimation in a contemporary Western Australian population using the Tanner-Whitehouse method

Various age estimation techniques have been utilised in Australia to evaluate the age of individuals who do not have documentation to determine legal majority/culpability. These age estimation techniques rely on the assessment of skeletal development as visualised in radiographs, CT scans, MRI or ultrasound modalities, and subsequent comparison to reference standards. These standards are not always population specific and are thus known to be less accurate when applied outside of the original reference sample, leading to potential ethical implications. Therefore, the present study aims to: (i) explore the variation in developmental trajectories between the established Tanner-Whitehouse (TW) age estimation standards and a Western Australian population; and (ii) develop specific hand-wrist age estimation standards for the latter population. The present study examines digital anterior-posterior hand-wrist radiographs of 360 individuals 0 to 24.9 years of age, equally represented by sex. Each radiograph was assessed using the RUS, Carpal and 20-bone methods of Tanner et al. The standard error of the estimate (SEE) was calculated for each method (range: ♀ SEE ±0.4-11.5 years; ♂ SEE ±0.9-10.1 years). The most accurate method was TW3 RUS for females and the TW2 Carpal system for males. The 50th centile skeletal maturity scores for each year age group were plotted against average chronological age to produce polynomial regression standards with a demonstrated accuracy of (♀ SEE ±0.09-3.46 years; ♂ SEE ±0.02-3.42 years) for females and males, respectively. The standards presented here can be used in future forensic investigations that require age estimation of hand-wrist bones in a Western Australian population, however, they are not appropriate for establishing age of majority (18 years), as skeletal maturity was attained on average earlier than 15 years of age in both sexes for all three systems examined.

Evolutionary psychology in the modern world: applications, perspectives, and strategies

An evolutionary approach is a powerful framework which can bring new perspectives on any aspect of human behavior, to inform and complement those from other disciplines, from psychology and anthropology to economics and politics. Here we argue that insights from evolutionary psychology may be increasingly applied to address practical issues and help alleviate social problems. We outline the promise of this endeavor, and some of the challenges it faces. In doing so, we draw parallels between an applied evolutionary psychology and recent developments in Darwinian medicine, which similarly has the potential to complement conventional approaches. Finally, we describe some promising new directions which are developed in the associated papers accompanying this article.

Evolutionary psychology in the modern world: applications, perspectives, and strategies

An evolutionary approach is a powerful framework which can bring new perspectives on any aspect of human behavior, to inform and complement those from other disciplines, from psychology and anthropology to economics and politics. Here we argue that insights from evolutionary psychology may be increasingly applied to address practical issues and help alleviate social problems. We outline the promise of this endeavor, and some of the challenges it faces. In doing so, we draw parallels between an applied evolutionary psychology and recent developments in Darwinian medicine, which similarly has the potential to complement conventional approaches. Finally, we describe some promising new directions which are developed in the associated papers accompanying this article.