The association of grandmaternal and maternal factors with maternal adult stature

Coming to the Caribbean-acclimation of Rhesus macaques (Macaca mulatta) at Cayo Santiago

OBJECTIVES

To investigate whether the Cayo Santiago, Puerto Rico (Latitude: 18.1564°N; temperature range 19°C to 32°C) rhesus macaque population has acclimated to their tropical island conditions since arriving from Lucknow, India (Latitude: 26.8470°N; temperature range 8°C to 41°C) in 1938.

MATERIALS AND METHODS

Using the derived skeletal collection, measurements were taken of long bone lengths, diaphyseal circumference, and body weight using 635 (237 males and 398 females) skeletally mature individuals. Measurements sampled colony members born over a 51-year time span at Cayo Santiago, from 1951 to 2002.

RESULTS

Results demonstrated that body weights and diaphyseal circumferences significantly declined in both males and females. Long bone lengths relative to body weight and diaphyseal circumference also increased in females. Whereas body weight, long bone length and diaphyseal circumference declined at near parallel rates in males.

DISCUSSION

The population has acclimated to homogenous, tropical, conditions of the Caribbean island since their arrival over 80 years ago. Trends in both sexes aligned with Bergmann's rule, though females displayed a greater decline in body weight, as well as greater affinity with Allen's rule, than did males. Buffering effects related to male competition may be responsible for this discrepancy. Overall, the Cayo Santiago populations, as shown over a significant period (1951-2002) of their history, have acclimated to their island conditions by decreasing in size and altering body proportions.

Intergenerational transmission of height in a historical population: From taller mothers to larger offspring at birth (and as adults)

Changes in growth and height reflect changes in nutritional status and health. The systematic surveillance of growth can suggest areas for interventions. Moreover, phenotypic variation has a strong intergenerational component. There is a lack of historical family data that can be used to track the transmission of height over subsequent generations. Maternal height is a proxy for conditions experienced by one generation that relates to the health/growth of future generations. Cross-sectional/cohort studies have shown that shorter maternal height is closely associated with lower birth weight of offspring. We analyzed the maternal height and offspring weight at birth in the maternity hospital in Basel, Switzerland, from 1896 to 1939 (N = ∼12,000) using generalized additive models (GAMs). We observed that average height of the mothers increased by ∼4 cm across 60 birth years and that average birth weight of their children shows a similarly shaped and upward trend 28 years later. Our final model (adjusted for year, parity, sex of the child, gestational age, and maternal birth year) revealed a significant and almost linear association between maternal height and birth weight. Maternal height was the second most important variable modeling birth weight, after gestational age. In addition, we found a significant association between maternal height and aggregated average height of males from the same birth years at time of conscription, 19 years later. Our results have implications for public health: When (female/maternal) height increases due to improved nutritional status, size at birth-and subsequently also the height in adulthood of the next generation-increases as well. However, the directions of development in this regard may currently differ depending on the world region.

Neighborhood environmental exposures and incidence of attention deficit/hyperactivity disorder: A population-based cohort study

BACKGROUND

Emerging studies have associated low greenspace and high air pollution exposure with risk of child attention deficit/hyperactivity disorder (ADHD). Population-based studies are limited, however, and joint effects are rarely evaluated. We investigated associations of ADHD incidence with greenspace, air pollution, and noise in a population-based birth cohort.

METHODS

We assembled a cohort from administrative data of births from 2000 to 2001 (N ∼ 37,000) in Metro Vancouver, Canada. ADHD was identified by hospital records, physician visits, and prescriptions. Cox proportional hazards models were applied to assess associations between environmental exposures and ADHD incidence adjusting for available covariates. Greenspace was estimated using vegetation percentage derived from linear spectral unmixing of Landsat imagery. Fine particulate matter (PM_2.5) and nitrogen dioxide (NO₂) were estimated using land use regression models; noise was estimated using a deterministic model. Exposure period was from birth until the age of three. Joint effects of greenspace and PM_2.5 were analysed in two-exposure models and by categorizing values into quintiles.

RESULTS

During seven-year follow-up, 1217 ADHD cases were diagnosed. Greenspace was associated with lower incidence of ADHD (hazard ratio, HR: 0.90 [0.81-0.99] per interquartile range increment), while PM_2.5 was associated with increased incidence (HR: 1.11 [1.06-1.17] per interquartile range increment). NO₂ (HR: 1.01 [0.96, 1.07]) and noise (HR: 1.00 [0.95, 1.05]) were not associated with ADHD. There was a 50% decrease in the HR for ADHD in locations with the lowest PM_2.5 and highest greenspace exposure, compared to a 62% increase in HR in locations with the highest PM_2.5 and lowest greenspace exposure. Effects of PM_2.5 were attenuated by greenspace in two-exposure models.

CONCLUSIONS

We found evidence suggesting environmental inequalities where children living in greener neighborhoods with low air pollution had substantially lower risk of ADHD compared to those with higher air pollution and lower greenspace exposure.

Can shorter mothers have taller children? Nutritional mobility, health equity and the intergenerational transmission of relative height

This study develops the concept of nutritional mobility, defined here as the probability that a mother ranked low in her cohort's height distribution will have a child who attains a higher rank order. We demonstrate that rank-order regression provides a robust metric of health equity, revealing differences in opportunities for each child to reach their own growth potential. We estimate four indicators of nutritional mobility and test for associations between nutritional mobility and various local economic and environmental factors. Nutritional mobility has improved over time, and the nutrition environment contributes about 2.86 times as much as a mother's height to her child's expected rank in height-for-age. Populations with the least mobility are in Latin America, and the most mobility is in more urbanized areas of Africa and Asia. Rank-order mobility is an important aspect of health equity, offering valuable insight into the role of socioecological factors in nutrition improvement across generations.

Influence of maternal height on children's health status and mortality: A cross-sectional study in poor Roma communities in rural Serbia

To determine possible variations in children's health status and mortality associated with variations in maternal stature, an anthropometric and demographic study was conducted in a Roma population of poor socio-economic status in rural Serbia. Data were collected during several years of anthropological fieldwork. The sample consisted of 691 women, ranging from 16 to 80 years of age. In addition to stature, Roma women's demographics, reproductive history, reproductive outcomes and health status of their children were collected. The results provide evidence of a significant association between mother's stature and their children's health and mortality, with a shorter mother's stature predisposing children to poor health and survival outcomes. The findings could prompt development of a definition of short stature among Roma women to evaluate the risk based on height distribution among the general Roma population.

The New "Obstetrical Dilemma": Stunting, Obesity and the Risk of Obstructed Labour

The "obstetrical dilemma" refers to the tight fit between maternal pelvic dimensions and neonatal size at delivery. Most interest traditionally focused on its generic significance for humans, for example our neonatal altriciality and our complex and lengthy birth process. Across contemporary populations, however, the obstetrical dilemma manifests substantial variability, illustrated by differences in the incidence of cephalo-pelvic disproportion, obstructed labour and cesarean section. Beyond accounting for 12% of maternal mortality worldwide, obstructed labour also imposes a huge burden of maternal morbidity, in particular through debilitating birth injuries. This article explores how the double burden of malnutrition and the global obesity epidemic may be reshaping the obstetrical dilemma. First, short maternal stature increases the risk of obstructed labour, while early age at marriage also risks pregnancy before pelvic growth is completed. Second, maternal obesity increases the risk of macrosomic offspring. In some populations, short maternal stature may also promote the risk of gestational diabetes, another risk factor for macrosomic offspring. These nutritional influences are furthermore sensitive to social values relating to issues such as maternal and child nutrition, gender inequality and age at marriage. Secular trends in maternal obesity are substantially greater than those in adult stature, especially in low- and middle-income countries. The association between the dual burden of malnutrition and the obstetrical dilemma is therefore expected to increase, because the obesity epidemic is emerging faster than stunting is being resolved. However, we currently lack objective population-specific data on the association between maternal obesity and birth injuries. Anat Rec, 300:716-731, 2017. © 2017 Wiley Periodicals, Inc.

Practical Application of Linear Growth Measurements in Clinical Research in Low- and Middle-Income Countries

BACKGROUND/AIMS

Childhood stunting is a prevalent problem in low- and middle-income countries and is associated with long-term adverse neurodevelopment and health outcomes. In this review, we define indicators of growth, discuss key challenges in their analysis and application, and offer suggestions for indicator selection in clinical research contexts.

METHODS

Critical review of the literature.

RESULTS

Linear growth is commonly expressed as length-for-age or height-for-age z-score (HAZ) in comparison to normative growth standards. Conditional HAZ corrects for regression to the mean where growth changes relate to previous status. In longitudinal studies, growth can be expressed as ΔHAZ at 2 time points. Multilevel modeling is preferable when more measurements per individual child are available over time. Height velocity z-score reference standards are available for children under the age of 2 years. Adjusting for covariates or confounders (e.g., birth weight, gestational age, sex, parental height, maternal education, socioeconomic status) is recommended in growth analyses.

CONCLUSION

The most suitable indicator(s) for linear growth can be selected based on the number of available measurements per child and the child's age. By following a step-by-step algorithm, growth analyses can be precisely and accurately performed to allow for improved comparability within and between studies.

The intergenerational transmission of body mass index across countries

There is a worldwide epidemic of obesity. We are just beginning to understand its consequences for child obesity. This paper addresses one important component of the crisis; namely the extent to which adiposity, or more specifically, BMI, is passed down from one generation to the next. We find that the intergenerational elasticity of BMI is very similar across countries and relatively constant - at 0.2 per parent. Our substantive finding is that this elasticity is very comparable across time and countries - even if these countries are at very different stages of economic development. Quantile analysis suggests that this intergenerational transmission mechanism is substantively different across the distribution of children's BMI; more than double for the most obese children what it is for the thinnest children. These findings have important consequences for the health of the world's children.¹.

Economic Benefits of Investing in Women's Health: A Systematic Review

BACKGROUND

Globally, the status of women's health falls short of its potential. In addition to the deleterious ethical and human rights implications of this deficit, the negative economic impact may also be consequential, but these mechanisms are poorly understood. Building on the literature that highlights health as a driver of economic growth and poverty alleviation, we aim to systematically investigate the broader economic benefits of investing in women's health.

METHODS

Using the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) guidelines, we systematically reviewed health, gender, and economic literature to identify studies that investigate the impact of women's health on micro- and macroeconomic outcomes. We developed an extensive search algorithm and conducted searches using 10 unique databases spanning the timeframe 01/01/1970 to 01/04/2013. Articles were included if they reported on economic impacts stemming from changes in women's health (table of outcome measures included in full review, Table 1). In total, the two lead investigators independently screened 20,832 abstracts and extracted 438 records for full text review. The final review reflects the inclusion of 124 articles.

RESULTS

The existing literature indicates that healthier women and their children contribute to more productive and better-educated societies. This study documents an extensive literature confirming that women's health is tied to long-term productivity: the development and economic performance of nations depends, in part, upon how each country protects and promotes the health of women. Providing opportunities for deliberate family planning; healthy mothers before, during, and after childbirth, and the health and productivity of subsequent generations can catalyze a cycle of positive societal development.

CONCLUSIONS

This review highlights the untapped potential of initiatives that aim to address women's health. Societies that prioritize women's health will likely have better population health overall, and will remain more productive for generations to come.

Are there changes in the nutritional status of children of Oportunidades families in rural Chiapas, Mexico? A cohort prospective study

BACKGROUND

In Mexico, despite that the fact that several social programs have been implemented, chronic undernutrition is still a public health problem affecting 1.5 million children of <5 years. Chiapas ranks first in underweight and stunting at national level with a stunting prevalence of 31.4 % whereas for its rural population is 44.2 %. The purpose of this paper is to determine if the nutritional status of a cohort of children living in poor rural communities under Oportunidades has changed. We were interested in assessing the nutrition evolution of the children who were initially diagnosed as stunted and of those who were diagnosed as normal. Oportunidades is an anti-poverty program of the Mexican government consisting mainly in monetary transfers to the families living in alimentary poverty.

METHODS

A 9-year cohort prospective study was conducted with nutritional evaluations of 222 children. Anthropometric indices were constructed from measurements of weight, height, and age of the children whose nutritional status was classified following WHO standards.

RESULTS

The results showed that although these children were Oportunidades beneficiaries for 9 years and their families improved their living conditions, children still had a high prevalence of stunting (40.1 %) and 69.6 % had not recovered yet. Children who were initially diagnosed with normal nutritional status and became stunted 2 years later had a higher risk (relative risk (RR) 5.69, 2.95-10.96) of continuing stunted at school age and adolescence.

CONCLUSIONS

Oportunidades has not impacted, as expected, the nutritional status of the study population. These findings pose the question: Why has not the nutritional status of children improved, although the living conditions of their families have significantly improved? This might be the result of an adaptation process achieved through a decrease of growth velocity. It is important to make efforts to watch the growth of the children during their first 3 years of age, to focus on improving the diet of women at fertile age and pay special attention to environmental conditions to break the vicious cycle of malnutrition.

Intergenerational influences on the growth of Maya children: The effect of living conditions experienced by mothers and maternal grandmothers during their childhood

OBJECTIVES

To test the hypothesis that living conditions experienced by maternal grandmothers (F1 generation) and mothers (F2 generation) during their childhood are related to height and leg length (LL: height - sitting height) of their 6-to-8 year old children (F3 generation).

METHODS

From September 2011 to June 2012 we obtained height and LL, and calculated z-score values of these measurements for 109 triads (F1 , F2 , F3 ) who are Maya living in Merida, Yucatan, Mexico. Multiple regression models were adjusted to examine the relation of anthropometric and intergenerational socioeconomic parameters of F1 (house index and family size during childhood) and F2 (paternal job loss during childhood) with the z-score values of height and LL of F3 .

RESULTS

Children's height and LL were positively associated with maternal height and LL. This association was relatively stronger in LL. Better categories of grand-maternal house index were significantly associated with higher values of height and LL in grandchildren. Grand-maternal family size was positively related with LL, but not with height.

CONCLUSIONS

Our findings partially support the hypothesis that living conditions experienced by recent maternal ancestors (F1 and F2 ) during their growth period influence the growth of descendants (F3 ). Results suggest that LL is more sensitive to intergenerational influences than is total height and that the transition from a traditional rural lifestyle to urban conditions results in new exposures for risk in human physical growth.

Influence of Adult Knee Height, Age at First Birth, Migration, and Current Age on Adult Physical Function of Bangladeshi Mothers and Daughters in the United Kingdom and Bangladesh

In the United Kingdom, Bangladeshi women have the lowest self-reported levels of physical activity and some of the highest levels of metabolic disease of all ethnic groups. To better understand these risks for poor health we employed life course and intergenerational hypotheses to predict lower body physical function in a sample of 121 Bangladeshi mothers (40–70 years old) and one of their adult daughters (17–36 years old) living in Bangladesh or in the UK. For the mothers, older age and shorter knee height predicted reduced lower body physical function. Knee height is a biomarker of nutrition and health status between birth and puberty. Age at first birth did not have a significant effect. For daughters, older age and migration to the UK predicted reduced lower body physical function. We controlled for total stature and fatness in all analyses. UK-born daughters were taller than BD-born daughters living in the UK, mostly due to differences in knee height. These new findings support previous research indicating that early life health and adequate nutritional status, along with appropriate adult physical activity and diet, may decrease risks for poor physical function, morbidity, and premature mortality.

Epigenetics: What does it mean for paediatric practice?

'Epigenetics' involves the study of gene expression and the environmental exposures that influence expression. In paediatrics, it is recognized that different physiological and developmental stages of the young individual are affected by both genetic control and environmental influence. It appears that changes in gene expression - not changes in the DNA itself - can be passed on from one generation to another. The importance for paediatricians is recognizing disorders involving epigenetics, recording events during childhood that could affect epigenetic control of gene expression, and being aware of new therapies as they become available. Paediatricians need to be able to recognize the relevant risk factors.

Bony pelvic canal size and shape in relation to body proportionality in humans

Obstetric selection acts on the female pelvic canal to accommodate the human neonate and contributes to pelvic sexual dimorphism. There is a complex relationship between selection for obstetric sufficiency and for overall body size in humans. The relationship between selective pressures may differ among populations of different body sizes and proportions, as pelvic canal dimensions vary among populations. Size and shape of the pelvic canal in relation to body size and shape were examined using nine skeletal samples (total female n = 57; male n = 84) from diverse geographical regions. Pelvic, vertebral, and lower limb bone measurements were collected. Principal component analyses demonstrate pelvic canal size and shape differences among the samples. Male multivariate variance in pelvic shape is greater than female variance for North and South Africans. High-latitude samples have larger and broader bodies, and pelvic canals of larger size and, among females, relatively broader medio-lateral dimensions relative to low-latitude samples, which tend to display relatively expanded inlet antero-posterior (A-P) and posterior canal dimensions. Differences in canal shape exist among samples that are not associated with latitude or body size, suggesting independence of some canal shape characteristics from body size and shape. The South Africans are distinctive with very narrow bodies and small pelvic inlets relative to an elongated lower canal in A-P and posterior lengths. Variation in pelvic canal geometry among populations is consistent with a high degree of evolvability in the human pelvis.

Maternal education inequalities in height growth rates in early childhood: 2004 Pelotas birth cohort study

Socio-economic inequalities in attained height have been reported in many countries. The aim of this study was to explore the age at which maternal education inequalities in child height emerge among children from a middle-income country. Using data from the 2004 Pelotas cohort study from Brazil we modelled individual height growth trajectories in 2106 boys and 1947 girls from birth to 4 years using a linear spline mixed-effects model. We examined the associations of maternal education with birth length and trajectories of growth in length/height, and explored the effect of adjusting for a number of potential confounder or mediator factors. We showed linear and positive associations of maternal education with birth length and length/height growth rates at 0-3 months and 12-29/32 months with very little association at 3-12 months, particularly in boys. By age 4 years the mean height of boys was 101.06 cm (SE = 0.28) in the lowest and 104.20 cm (SE = 0.15) in the highest education category (mean difference 3.14 cm, SE = 0.32, P < 0.001). Among girls the mean height was 100.02 cm (SE = 0.27) and 103.03 cm (SE = 0.15) in the lowest and highest education categories, respectively (mean difference 3.01 cm, SE = 0.31, P < 0.001). For both boys and girls there was on average a 3-cm difference between the extreme education categories. Adjusting for maternal height reduced the observed birth length differences across maternal education categories, but differences in postnatal growth rates persisted. Our data demonstrate an increase in the absolute and relative inequality in height after birth; inequality increases from approximately 0.2 standard deviations of birth length to approximately 0.7 standard deviations of height at age 4, indicating that height inequality, which was already present at birth, widened through differential growth rates to age 2 years.

The intergenerational transmission of height: evidence from rural Vietnam

A growing body of work suggests that health may be transferred across generations. The aim of this paper is to examine the mechanisms that might account for observed intergenerational associations in health outcomes. Using data from Vietnam, this study analyzes intergenerational correlations in height, a measure of long-run health status, between parents and their children. Insights from biology and economics are used to motivate several strategies that collectively provide insight on the role and importance of different mechanisms. The results illustrate strong intergenerational associations in height, which remain stable with the inclusion of controls for parent and household characteristics. Maternal height is more strongly associated with the heights of boys than girls, while the associations with paternal height are similar across genders. The use of conditions faced by parents early in life as instruments for their height yields significantly larger estimates of the mother-child height association relative to OLS, while the estimated father-child associations move to zero. These results, in conjunction with those from several other tests, illustrate that non-genetic factors are important in determining parent-child associations in height, and more speculatively, that epigenetic mechanisms may play an important role. These findings illustrate the value of investments in early childhood, as these may confer intergenerational benefits.

Maternal capital and the metabolic ghetto: An evolutionary perspective on the transgenerational basis of health inequalities

There is particular interest in understanding socioeconomic and ethnic variability in health status. The developmental origins of disease hypothesis emphasize the importance of growth patterns across the life-course in relation to noncommunicable disease risk. The physiological components of cardiovascular risk, collectively termed the metabolic syndrome, derive in part from a disparity between the homeostatic "metabolic capacity" of vital organs and the "metabolic load" induced by large tissue masses, a rich diet and sedentary behavior. From an evolutionary perspective, the risk of such disparity is decreased by maternal physiology regulating offspring growth trajectory during gestation and lactation. Maternal capital, defined as phenotypic resources enabling investment in the offspring, allows effective buffering of the offspring from nutritional perturbations and represents the environmental niche initially occupied by the offspring. Offspring growth patterns are sensitive to the magnitude of maternal capital during early windows of plasticity. Offspring life-history strategy can then respond adaptively to further factors across the life-course, but only within the context of this initial maternal influence on growth. Maternal somatic capital is primarily gained or lost across generations, through variable rates of fetal and infant growth. I argue that the poor nutritional experience of populations subjected to colonialism resulted in a systematic loss of maternal capital, reflected in downward secular trends in stature. Accelerating the recovery of somatic capital within generations overloads metabolic capacity and exacerbates cardiovascular risk, reflected in increased disease rates in urbanizing and emigrant populations. Public health policies need to benefit metabolic capacity without exacerbating metabolic load.

Relationship between maternal and newborn anthropometric measurements in Sudan

BACKGROUND

The aim of the present study was to investigate the relationship between maternal and newborn anthropometry.

METHODS

In 1000 Sudanese mothers and newborns anthropometric measurements were taken within 24 h of birth. The relationship between maternal characteristics including age, years of education, social class and anthropometry, and newborn characteristics including gestational age, weight, body length, body circumference and skin-fold thickness, was investigated on multiple regression with backward selection, and multivariate anova (where appropriate) to identify the most important associations.

RESULTS

Maternal age and anthropometry were significantly associated with newborn anthropometry to a variable extent. The strongest associations (R2 > 5-6%) were found for mid-arm circumference, supine length and birthweight. The postpartum maternal lean body mass (LBM) was significantly associated with birthweight, body length and body circumference (P < 0.001), while skin-fold thickness was mainly associated with maternal age and maternal body mass index (BMI). Gestational age was only weakly associated with the maternal height (R2 > 1.3%) and the association between maternal anthropometry and the ponderal index (PI) of the newborn was negligible (R2 < 1%). Maternal education was significantly associated with birthweight and body circumference (except the abdominal), and the PI and the latter increased significantly with increasing number of years of education. No association between social class and newborn anthropometry was obtained.

CONCLUSION

There was a significant association between maternal LBM and newborn size and between maternal BMI and newborn fat stores. Maternal education and not social class was associated with newborn size.

The thrifty phenotype as an adaptive maternal effect

Human diseases in adulthood are increasingly associated with growth patterns in early life, implicating early-life nutrition as the underlying mechanism. The thrifty phenotype hypothesis proposed that early-life metabolic adaptations promote survival, with the developing organism responding to cues of environmental quality by selecting an appropriate trajectory of growth. Recently, some authors have proposed that the thrifty phenotype is also adaptive in the longer-term, by preparing the organism for its likely adult environment. However, windows of plasticity close early during human development, and subsequent environmental changes may result in the selected trajectory becoming inappropriate, leading to adverse effects on health. This paradox generates uncertainty as to whether the thrifty phenotype is indeed adaptive for the offspring in humans. The thrifty phenotype should not be considered a dichotomous concept, rather it refers to the capacity of all offspring to respond to environmental information during early ontogenetic development. This article argues that the thrifty phenotype is the consequence of three different adaptive processes - niche construction, maternal effects, and developmental plasticity - all of which in humans are influenced by our large brains. While developmental plasticity represents an adaptation by the offspring, both niche construction and parental effects are subject to selection on parental rather than offspring fitness. The three processes also operate at different paces. Human offspring do not become net calories-producers until around 18 years of age, such that the high energy costs of the human brain are paid primarily by the mother, even after weaning. The evolutionary expansion of human brain volume occurred in environments characterised by high volatility, inducing strong selective pressure on maternal capacity to provision multiple offspring simultaneously. The thrifty phenotype is therefore best considered as a manipulation of offspring phenotype for the benefit of maternal fitness. The information that enters offspring phenotype during early development does not predict the likely future environment of the offspring, but rather reflects the mother's own developmental experience and the quality of the environment during her own maturation. Offspring growth trajectory thus becomes aligned with long-term maternal capacity to provision. In contemporary populations, the sensitivity of offspring development to maternal phenotype exposes the offspring to adverse effects, through four distinct pathways. The offspring may be exposed to (1) poor maternal metabolic control (e.g. gestational diabetes), (2) maternally derived toxins (e.g. maternal smoking), or (3) low maternal social status (e.g. small size). Adverse consequences of these effects may then be exacerbated by (4) exposure either to the "toxic" western environment in postnatal life, in which diet and physical activity levels are mismatched with metabolic experience in utero, or at the other extreme to famine. The rapid emergence of the epidemic of the metabolic syndrome in the 20th Century reflects the rapid acceleration in the pace of niche construction relative to the slower physiological combination of developmental plasticity and parental effects.