Jonathan CK Wells

• Doctor of Philosophy
• Professor at University College London

Over recent millennia, human populations have regularly reconstructed their subsistence niches, changing both how they obtain food and the conditions in which they live. For example, over the last 12,000 years the vast majority of human populations shifted from foraging to practicing different forms of agriculture. The shift to farming is widely un...

Despite being globally pervasive, racism, xenophobia, and discrimination are not universally recognised determinants of health. We challenge widespread beliefs related to the inevitability of increased mortality and morbidity associated with particular ethnicities and minoritised groups. In refuting that racial categories have a genetic basis and a...

Evidence for a reduction in stature between Mesolithic foragers and Neolithic farmers has been interpreted as reflective of declines in health, however, our current understanding of this trend fails to account for the complexity of cultural and dietary transitions or the possible causes of phenotypic change. The agricultural transition was extended...

There is growing concern with social disparities in health, whether relating to gender, ethnicity, caste, socio-economic position or other axes of inequality. Despite addressing inequality, evolutionary biologists have had surprisingly little to say on why human societies are prone to demonstrating exploitation. This article builds on a recent book...

In uncomplicated pregnancies, birthweight is inversely associated with adult non-communicable disease (NCD) risk. One proposed mechanism is maternal malnutrition during pregnancy. Another explanation is that shared genes link birthweight with NCDs. Both hypotheses are supported, but evolutionary perspectives address only the environmental pathway....

Background: Ultra-endurance athletics, such as transoceanic rowing, imposes significant physiological stress, leading to muscle catabolism and alterations in immune function. A case series pilot study from our laboratory suggests that the central nervous system may mirror these changes through a pattern of disproportionately high beta brainwave vol...

The adaptive and independent interrelationships between different body composition components have been identified as crucial determinants of disease risk. On the basis of this concept, the load-capacity model of body composition, which utilizes measurements obtained through nonanthropometric techniques such as dual-energy X-ray absorptiometry, was...

Objective Childhood obesity is increasing in many countries, including Kuwait. Currently, adiposity is most commonly assessed from simple anthropometric measurements, e.g. height and weight or combined as body mass index (BMI). This is despite these surrogate measurements being poor indices of adiposity. Bioelectrical impedance analysis (BIA) is a...

Background While most studies of adults with a history of severe acute malnutrition (SAM) focused on survival and long-term non-communicable diseases, few studies have examined community health. The aim of this study was to compare the overall health status and its predictors between adults with a history of SAM and healthy controls in the context...

Background Malnutrition during pregnancy is associated with adverse birth outcomes, but the importance of maternal diet during pregnancy for neonatal body composition remains inconclusive. This study investigated the role of maternal diet during pregnancy for neonatal body composition in the Ethiopian iABC birth cohort. Methods The data stemmed fr...

Background Children with stunting are at risk of infections. We assessed the effect of lipid-based nutrient supplement (LNS) on morbidity in children with stunting. Methods This was a secondary analysis of a randomized, 2×2 factorial trial among 12–59 months-old, stunted children in Uganda. Children were randomized to LNS containing milk or soy pr...

Objectives We aimed to test if different subsistence patterns shaped different antenatal eating behaviors in Madagascar, and to investigate if reasons given for maternal dietary restrictions disclosed actual biological pressures on pregnancy. Material and Methods We conducted semi‐structured interviews with 312 participants to investigate differen...

This study aimed to identify the determinants of infant growth in terms of length‐for‐age z‐score (LAZ) in a birth cohort (n = 602) in the plains of Nepal. Children were enrolled within 72 h of birth and followed‐up every 28 days until they were 2 years. We fitted mixed‐effects linear regression models controlling for multiple measurements within i...

Objectives: Rapid weight gain in infancy is associated with an increased risk of later adiposity. Very rarely, however, exclusively breastfed infants experience excessive weight gain (EWG) during the period of exclusive breastfeeding (EBF) when breast milk is the only source of nutrition. We investigated growth and body composition at 36 months in...

Introduction Maternal nutrition promotes maternal and child health. However, most interventions to address undernutrition are only implemented once pregnancy is known, and cannot address broader risk factors preceding conception. Poverty and socio-economic status are considered systemic risk factors, but both economic growth and cash transfers have...

Introduction Globally in 2024, 1 in 5 women aged 20–24 years worldwide had been married before the age of 18 years. One reason for this persistent prevalence of underage marriage may be the slow change in social norms relating to education levels and women's marriage age. However, we know little about how norms change, and whether they vary by soci...

Assessment of body composition can be useful in managing many clinical or public health conditions, including HIV. Most people living with HIV infection are in Africa where clinics may lack equipment, utilities or staff time for optimal body composition assessment. Thus, it is important to determine whether less expensive and more available and sca...

Background Childhood is a period marked by dynamic growth. Evidence of the association between childhood linear growth and school achievement comes mostly from cross-sectional data. We assessed associations between birth length, childhood linear growth velocities, and stunting with school achievement. Methods Newborns were recruited into the Ethio...

Background Few trials have explored long-term effects of interventions designed to reduce child stunting. We evaluated school-age outcomes in rural Zimbabwean children who received cluster-randomised water, sanitation and hygiene (WASH) and/or infant and young child feeding (IYCF) interventions from pregnancy up to 18 months of age. Methods The Sa...

Introduction: This pilot study was designed to test the hypothesis that quantitative electroencephalographic (qEEG) measurements reflect physiological adaptations for brain energy reallocation. The study focused on a team of three well-matched male rowers participating in a 30-day, 2,650-mile continuous transatlantic rowing competition, examining t...

Evolutionary perspectives on obesity have been dominated by genetic frameworks, but plastic responses are also central to its aetiology. While often considered a relatively modern phenomenon, obesity was recorded during the Palaeolithic through small statuettes of the female form (Venus figurines). Even if the phenotype was rare, these statuettes i...

Early childhood growth is associated with cognitive function. However, the independent associations of fat mass (FM) and fat-free mass (FFM) with cognitive function are not well understood. We investigated associations of FM and FFM at birth and 0-5 years accretion with cognitive function at 10 years. Healthy term newborns were enrolled in this coh...

The prevalence of poor linear growth among African children with perinatally acquired HIV remains high. There is concern that poor linear growth may to lead to later total and central fat deposition and associated non-communicable disease risks. We investigated associations between height-for-age Z score (HAZ) and total and regional fat and lean ma...

The expensive-tissue hypothesis (ETH) posited a brain–gut trade-off to explain how humans evolved large, costly brains. Versions of the ETH interrogating gut or other body tissues have been tested in non-human animals, but not humans. We collected brain and body composition data in 70 South Asian women and used structural equation modelling with in...

Background Globally, over 16 million children were exposed to HIV during pregnancy but remain HIV-free at birth and throughout childhood by 2022. Children born HIV-free (CBHF) have higher morbidity and mortality and poorer neurodevelopment in early life compared to children who are HIV-unexposed (CHU), but long-term outcomes remain uncertain. We ch...

Maternal/caregivers’ mental health (MMH) and child nutrition are both poor in low- and middle-income countries. Links between the two are plausible but poorly researched. Our aim was to inform future malnutrition management programmes by better understanding associations between MMH and nutritional status of infants aged under six month (u6m). We c...

Introduction In the context of adverse in utero environments, the fetal brain might be preserved at the expense of other tissues. This trade‐off, brain sparing, has not been studied in the context of maternal infection. We investigated cases of maternal syphilis in the early 20th century and influenza during the 1918–1920 pandemic, in the Swiss cit...

Background Women’s underage marriage (<18 years) is associated with adverse maternal and child health outcomes. Poverty in the natal household has been widely considered to be a key risk factor for underage marriage, but the evidence base is unreliable. When investigating this issue, most studies use marital wealth inappropriately, as a proxy for w...

End-stage chronic liver disease (ESCLD) is associated with aberrations of systemic metabolism like sarcopenia and low respiratory quotient (RQ) linked to gluconeogenesis and fatty acid oxidation. We wanted to investigate correlations between genes expressed in the liver with genes expressed in muscle and adipose tissue in the context of childhood E...

Background Breast milk is the gold standard for infant feeding. It is a dynamic biological fluid rich in numerous bioactive components. Emerging research suggests that these components, including hormones, may serve as signals between mother and offspring. From an evolutionary perspective, maternal hormonal signals could allow co-adaptation of mate...

Human evolutionary demography is an emerging field blending natural science with social science. This edited volume provides a much-needed, interdisciplinary introduction to the field and highlights cutting-edge research for interested readers and researchers in demography, the evolutionary behavioural sciences, biology, and related disciplines. By...

Obesity is fundamentally a condition where physiology and behavior of individuals meet the environment, and the emerging global obesity pandemic reflects the contribution of a wide range of cultural, societal, economic and systemic driving forces. Today, different areas of obesity research are relatively separated from each other in discrete silos,...

Objective In South Asia, studies show secular trends toward slightly later women's marriage and first reproduction. However, data on related biological and social events, such as menarche and age of coresidence with husband, are often missing from these analyses. We assessed generational trends in key life events marking the transition to womanhood...

The UK Covid-19 New Mum Study (cross-sectional study) recorded maternal experience during the early stages of the pandemic. Our previous analyses showed that the pandemic and 2020 national lockdown negatively impacted maternal mental health. Here, we describe changes in infant behaviour (crying and fussiness) reported by the mother during the Covid...

Background: This secondary analysis of data from a randomized controlled trial (RCT) investigated how the maternal gut, breast milk, and infant gut microbiomes may contribute to the effects of a relaxation intervention, which reduced maternal stress and promoted infant weight gain. Methods: An RCT was undertaken in healthy Chinese primiparous mothe...

Maternal/caregivers’ mental health (MMH) and child nutrition are both poor in low- and middle-income countries. Links between the two are plausible but poorly researched. Our aim was to inform future malnutrition management programmes by better understanding associations between MMH and the nutritional status of infants aged u6m. We conducted a hea...

Background: This study explored maternal gut, breast milk and infant gut microbiomes as possi-ble mediators of the observed effects of a relaxation intervention which reduced maternal stress and promoted infant weight gain. Methods: A randomized controlled trial was conducted in healthy Chinese primiparous mother-infant pairs. Mothers were randomly...

People are increasingly encouraged to reduce animal food consumption and shift towards plant-based diets; however, the implications for children’s health are unclear. In this narrative review of research in high-income settings, we summarize evidence on the increasing consumption of plant-based diets in children and update an earlier systematic rev...

Background Bioelectrical impedance vector analysis (BIVA) is a non-invasive approach to assessing body composition and cellular health, which may improve the assessment of nutritional status in sick children. We explored the reliability, clinical utility, and acceptability of BIVA, as an indicator of nutritional status for children under five years...

People are increasingly encouraged to reduce animal food consumption and shift towards plant-based diets, however the implications for children’s health are unclear. In this narrative review of research in high-income settings, we summarize evidence on the increasing consump-tion of plant-based diets in children, and update an earlier systematic re...

Background Stress during pregnancy is detrimental to maternal health, pregnancy and birth outcomes and various preventive relaxation interventions have been developed. This systematic review and meta-analysis aimed to evaluate their effectiveness in terms of maternal mental health, pregnancy and birth outcomes. Method The protocol for this review...

Background Globally, over 16 million children were exposed to HIV during pregnancy but remain HIV-free at birth and throughout childhood. Children born HIV-free (CBHF) have higher morbidity and mortality and poorer neurodevelopment in early life compared to children who are HIV-unexposed (CHU), but long-term outcomes remain uncertain. We characteri...

Background Admission criteria that treat children with low mid-upper-arm circumference (MUAC), and low weight-for-height z-score (WHZ) are not aligned with the evidence on which children are at risk of mortality. An analysis of community-based cohort data from Senegal found that a combination of weight-for-age (WAZ) and MUAC criteria identified all...

Background Bioelectrical impedance vector analysis (BIVA) is a non-invasive approach to assessing body composition and cellular health, which may improve the assessment of nutritional status in sick children. We explored the reliability, clinical utility, and acceptability of BIVA, as an indicator of nutritional status for children under five years...

Background Body composition could help identify malnutrition in pediatric patients, but there is uncertainty over which techniques are most suitable and prevailing opinion that measurements are difficult to obtain in practice. This study examined the acceptability, practicality, reliability, and validity of different anthropometric and body composi...

Nutritional rehabilitation during severe acute malnutrition (SAM) aims to quickly restore body size and minimize poor short-term outcomes. We hypothesized that faster weight gain during treatment is associated with greater cardiometabolic risk in adult life. Anthropometry, body composition (DEXA), blood pressure, blood glucose, insulin and lipids w...

Age and sex influence the risk of childhood wasting. We aimed to determine if wasting treatment outcomes differ by age and sex in children under 5 years, enroled in therapeutic and supplementary feeding programmes. Utilising data from stage 1 of the ComPAS trial, we used logistic regression to assess the association between age, sex and wasting tre...

(1) Background: Breastfeeding (BF) has been shown to lower the risk of overweight and cardiometabolic disease later in life. However, evidence from low-income settings remains sparse. We examined the associations of BF status at 6 months with anthropometry, body composition (BC), and cardiometabolic markers at 5 years in Ethiopian children. (2) Met...

Introduction Given the increasing incidence of chronic degenerative diseases related to changes in tissues, the availability of diagnostic tools with greater accuracy in the estimation of body composition (BC) has become necessary. Interpreting the BC values of individuals requires reference data obtained from a healthy population with the same eth...

Introduction Maternal capital (MC) is a broad term from evolutionary biology, referring to any aspects of maternal phenotype that represent resources available for investment in offspring. We investigated MC in breastfeeding mothers of late preterm and early term infants, examining its relationship with infant and breastfeeding outcomes. We also de...

There is considerably greater variation in metabolic rates between men than between women, in terms of basal, activity and total (daily) energy expenditure (EE). One possible explanation is that EE is associated with male sexual characteristics (which are known to vary more than other traits) such as musculature and athletic capacity. Such traits m...

It has been argued that enhanced phenotypic plasticity and life-history variability, in addition to a greater adaptive dependence on social learning, behavioral flexibility, and niche construction, are characteristics of the hominin lineage that accommodated both environmental variation and the colonization of new environments. The extended evoluti...

Background Globally, 80% of cardiovascular diseases (CVD) occur in low- and middle-income countries. Many CVD risk factors have their origins in early-life. We investigated (1) how growth trajectories from childhood to late-adolescence and socio-economic disparities in growth have changed in China; (2) how childhood BMI trajectories were associated...

Background Bioelectrical impedance analysis (BIA) is a technique widely used for estimating body composition and health-related parameters. The technology is relatively simple, quick, and non-invasive, and is currently used globally in diverse settings, including private clinicians’ offices, sports and health clubs, and hospitals, and across a spec...

Early growth has long-lasting associations with adult metabolic health. However, the association of adiposity with cardiometabolic risk factors in toddlers remains poorly understood. This study aimed to examine the association of maternal prenatal factors and child adiposity with child cardiometabolic risk factors among boys and girls aged 2 years....

Objectives: Evolutionary life history theory has a unique potential to shed light on human adaptive capabilities. Ultra-endurance challenges are a valuable experimental model allowing the direct testing of phenotypic plasticity via physiological trade-offs in resource allocation. This enhances our understanding of how the body prioritizes differen...

Evolutionary perspectives on obesity have aimed to understand how the genetic constitution of individuals has been shaped by selective pressures such as famine, predation or infectious disease. The dual intervention model assumes strong selection on lower and upper limits of adiposity, but negligible fitness implications for intermediate adiposity....

Background : There is a need for follow-up of early-life stunting intervention trials into childhood to determine their long-term impact. A holistic school-age assessment of health, growth, physical and cognitive function will help to comprehensively characterise the sustained effects of early-life interventions. Methods: The Sanitation Hygiene Inf...

Background and objectives In patrilocal societies, married women typically co-reside with their parents-in-law, who may act in their son’s reproductive interests. These relationships may shape maternal mental health and autonomy. Few studies examined these dynamics from an evolutionary perspective. Theoretically, marital kin may increase their fitn...

Background: Preterm birth has been associated with increased risk of hypertension and cardiovascular disease later in adulthood, attributed to cardiovascular and metabolic alterations in early life. However, there is paucity of evidence from low- and middle-income countries (LMICs). Methods: We investigated the differences between preterm (<37 w...

Compared to other primates, modern humans face high rates of maternal and neonatal morbidity and mortality during childbirth. Since the early 20th century, this "difficulty" of human parturition has prompted numerous evolutionary explanations, typically assuming antagonistic selective forces acting on maternal and fetal traits, which has been terme...

Aims/hypothesis Low birthweight is a risk factor for type 2 diabetes. Most previous studies are based on cross-sectional prevalence data, not designed to study the timing of onset of type 2 diabetes in relation to birthweight. We aimed to examine associations of birthweight with age-specific incidence rate of type 2 diabetes in middle-aged to older...

Background: Though birth weight (BW) has been associated with later cardiovascular disease and type 2 diabetes, the role of birth fat mass (BFM) and birth fat-free mass (BFFM) on cardiometabolic health is unclear. Objective: To examine associations of BW, BFM, and BFFM with later anthropometry, body composition, abdominal fat, and cardiometaboli...

Background Neither the global population nor individual countries have reached the WHO target of ≥50% infants exclusively breastfed (EBF) until 6 months. This may partly be due to perceptions of insufficient milk and energy supply to meet the needs for rapid growth and development. Objective In a longitudinal observational study, our aim was to de...

Background Despite possible benefits for growth, milk is costly to include in foods for undernourished children. Furthermore, the relative effects of different milk components, milk protein (MP), and whey permeate (WP) are unclear. We aimed to assess the effects of MP and WP in lipid-based nutrient supplement (LNS), and of LNS itself, on linear gro...

Background Stress during pregnancy is associated with perturbances in maternal psychology and physiology, and results in adverse pregnancy and birth outcomes. However, little attention has been given to understand maternal stress and its potential negative consequences in many low- and middle-income countries. We aimed to investigate whether pregna...

Introduction We developed the School-Age Health, Activity, Resilience, Anthropometry and Neurocognitive (SAHARAN) toolbox to address the shortage of school-age assessment tools that combine growth, physical and cognitive function. Here we present i) development, acceptability and feasibility of the SAHARAN toolbox; ii) characteristics of a pilot co...

Exercise physiologists and evolutionary biologists share a research interest in determining patterns of energy allocation during times of acute or chronic energetic scarcity.. Within sport and exercise science, this information has important implications for athlete health and performance. For evolutionary biologists, this would shed new light on o...

Background Admissions criteria which treat children with low mid-upper-arm circumference (MUAC), low weight-for-height z-score (WHZ) are not aligned with the evidence on which children are at risk of mortality. An analysis of community-based cohort data from Senegal found that a combination of weight-for-age (WAZ) and MUAC criteria identified all c...

Objective: Explore patterns of post-malnutrition growth (PMGr) during and after treatment for severe malnutrition, and describe associations with survival and non-communicable disease (NCD) risk seven years post-treatment. Design: Six indicators of PMGr were derived based on a variety of timepoints, weight, weight-for-age z-score (WAZ) and heigh...

Being born with appropriate weight-for-gestational age (AGA, ~80% of newborns) is often considered as low risk for future obesity. This study examined differential growth trajectories in the first two years by considering pre- and peri-natal factors among term-born AGA infants. We prospectively investigated 647 AGA infants and their mothers enrolle...

The first 1000 days of life represents a critical period for lifelong metabolic health. This study prospectively examined the contrasts between the growth trajectories of large, small, and appropriate sizes for gestational age (LGA, SGA, and AGA) term-born infants in their first two years, and their blood pressure at two years. In 2012–2013, 806 Ch...

Background: Early growth and body composition may influence risk of obesity and health in adulthood. Few studies have examined how undernutrition is associated with body composition in early life. Objective: We assessed stunting and wasting as correlates of body composition in young Kenyan children. Methods: Nested in a randomized controlled n...

The consequences for adolescent health due to early life exposure to natural disasters combined with war are not known. We collected data from adolescents aged 12-13 years in Sri Lanka whose mothers were pregnant during the Indian Ocean tsunami in 2004 in a tsunami-affected region (n = 22), conflict-affected region (n = 35), conflict-plus-tsunami-a...

HIV and severe wasting are associated with post-discharge mortality and hospital readmission among children with complicated severe acute malnutrition (SAM); however, the reasons remain unclear. We assessed body composition at hospital discharge, stratified by HIV and oedema status, in a cohort of children with complicated SAM in three hospitals in...

Background: Stress occurring during pregnancy is associated with perturbances in maternal psychology and physiology, and results in adverse pregnancy and birth outcomes. However, little attention has been given to understand maternal stress and its potential negative consequences in many low- and middle-income countries. We aimed to investigate whe...

Background: Maternal stress is one modifiable variable that could influence mother-infant signaling and negatively affect breastfeeding and infant growth. Objectives: This study aimed to test the hypothesis that relaxation therapy would reduce maternal stress and improve infant growth, behavior, and breastfeeding outcomes after late preterm (LP)...