Life history theory seeks to understand how organisms distribute energy between physiological functions across the life course. A central assumption is that energy allocation involves 'trade-offs' between competing functions relating to defence, maintenance, reproduction, and growth. Constraints on human energy expenditure may produce trade-offs during energetic stress, affecting functions critical for homeostasis, survival, and reproduction. While there is some evidence for binary trade-offs between two functions in humans, no studies have tested physiological resource prioritisation across multiple functions under energetic constraint. This study empirically assessed multiple human life history trade-offs and the proximate biological mechanisms underpinning them. We recruited 147 ultra-endurance athletes (107 male, 40 female) participating in four environmentally diverse multiday ultramarathons and one multiweek ocean rowing event. The severe energetic demands of these competitions provide a valuable opportunity to provoke and observe detectable trade-offs. We found evidence of trade-offs across multiple functions. Specifically, investment in defence (as indexed by immune biomarkers) was broadly prioritised relative to investment in storage, reproduction and maintenance. Our results enhance current understanding of the role of phenotypic plasticity in human adaptability and have implications for athlete health and performance as well as the emerging discipline of evolutionary public health.

Paleoanthropology and archaeology employ various proxy measures of hominin cognition, including endocranial volume, the complexity of material culture, or encephalization quotients (EQ). Competing scenarios of hominin encephalization contrast gradual anagenetic change with punctuated models linked to speciation events and major technological innovations. Here, we employ improved estimates of EQ with increased spatiotemporal resolution, including a novel paleodeme approach, and examine their relationship with technological complexity. We found no substantial increase in hominin encephalization associated with the earliest stone tool technologies, the origin of our genus, or the onset of the Acheulean. Instead, segmented regression analysis identified a major breakpoint in encephalization at ~ 1.2–0.7 Mya and another inflection point at ~ 0.1 Mya. Measures of technological complexity correlate highly with EQ, demonstrating a tight, though late, integration of encephalization with cultural evolution. Exponential increases in relative brain size emerge only after the onset of the Middle Paleolithic/Middle Stone Age, coinciding with a marked acceleration in both the diversity and pace of cultural innovation during the Late Pleistocene. Our findings support a model of late, stepwise encephalization co-evolving with cumulative cultural complexity. Significance statement Our understanding of human evolution has long assumed that larger brains evolved gradually alongside the earliest stone tools and major technological innovations. We overturn this view by showing that substantial increases in relative brain size occurred much later than previously thought, characterized by a stepwise pattern that coincided with accelerating cultural innovation during the Middle to Late Pleistocene. These findings demonstrate that the evolution of larger brains and increasingly complex culture became tightly coupled only late in human history. This offers a revised biocultural framework for understanding the emergence of modern humans, proving that early technological milestones did not drive initial brain expansion, but that biology and culture later formed an accelerating, co-evolutionary feedback loop.

IntroductionEndurance activity is considered a hallmark of human evolution, but there is limited understanding of what constrains this capacity. The renal demands of endurance exercise often elicit cellular damage, and renal functional capacity is shaped by fetal growth, but whether birth weight (BW) directly affects exercise-induced renal damage is unknown.MethodsHere, we test the extent to which birth weight shapes change in serum creatinine, a marker of kidney function, among 44 ultramarathon athletes racing in hot or cold conditions.ResultsOn their own, sex, age, distance run, hydration status, and muscle damage explained ~33% of the variance in absolute creatinine change (p=0.009). The addition of linear and quadratic mean-centered birth weight terms and ultramarathon race significantly improved the model fit (p<0.01), explaining ~58% of the variance in absolute creatinine change across the races (p<0.001). In this model, hydration status and both birth weight terms were the significant predictors of creatinine change (all p<0.05), indicating that both low and high birth weights were associated with a higher chance of transient elevation in creatinine after prolonged exercise. Holding all other variables constant, birth weight influences the kidney’s response to endurance exercise in a U-shaped manner, with the lowest increases in creatinine predicted at birth weights of ~3.8 kg.DiscussionRenal functional capacity, proxied by BW, may thus have been central in constraining the upper limits of endurance activity in human evolution, helping us to understand why not just inadequate, but too much, physical activity can impair health.

[This corrects the article DOI: 10.7759/cureus.84059.].

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 differences in avoided food types during pregnancy, reasons, and infants' weight between subsistence patterns (agriculture, agriculture-husbandry/fishery, fishery), and associations between food types and reasons (Chi-squared, Fisher's, and Kruskal-Wallis test in R and SPSS). Secondary questions investigated regional variance in food avoidance (PCA), the association between the carbohydrate content of avoided foods and the fear of difficult delivery (regression analysis), and institutional and non-institutional influences on dietary proscriptions (heatmap). RESULTS:Agriculturalists avoided more plant-based foods than fishers for the fear of difficult delivery due to large infants. Infants' weights at birth did not vary significantly across subsistence modes. Dietary norms were reinforced by an interplay between institutional and non-institutional advisors. CONCLUSIONS:Food avoidances during pregnancy among Malagasy agriculturalists and fishers differ in targets and reasons. Avoided foods reflect staple diets, while the fear of difficult labor due to large infant size in relation to carbohydrate-rich foods among agriculturalists overlaps with a high incidence of obstructed labor in agricultural regions. Therefore, different subsistence modes affect antenatal behavior priorities differently. Taboos and sources of advice on maternal diet are fluid systems. We highlight the urgent need to better understand the determinants of obstructed labor and the patterns of spread of antenatal practices in Madagascar.

ABSTRACT Objectives To investigate the developmental changes in the human calcaneal internal and external morphology linked to the acquisition of mature bipedal locomotion. Methods Seventy seven micro‐CT scans of modern juvenile calcanei (from perinates to 15 years old) are employed. The chronological period spans from the Middle/Late Neolithic (4800–4500 BCE) to the 20th century. Through a comprehensive approach that comprises geometric morphometric methods and whole‐bone trabecular analysis, the calcaneal growing morphology has been explored. Results Morphological changes reflect the development of bipedal locomotion, showing its potential when tracking the major locomotor milestones. The calcaneal shape is immature and almost featureless during the first year of life. The internal architecture is dense and isotropic with numerous thin trabeculae closely packed together. The internal architecture changes to better adapt to variations in load stimulated by a more mature gait by increasing bone mass and alignment, with fewer and thicker struts. The external morphology shows its plasticity by increasing the surface area where greater strain is expected and changing the orientation of the articular facets. Conclusions Analysis of morphological changes in the growing calcaneus highlights the importance of an integrative methodology when exploring developmental bone plasticity. The changes in calcaneal internal and external morphologies reflect the different loading patterns experienced during growth, gradually shifting from a more generalized morphology to a more adult‐like one, reflecting major locomotor achievement. Our research shows that although initially genetically driven, calcaneal plasticity may display mechanical influences and provide precious information on tracking the main locomotor milestones.

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 the effects of extreme, prolonged stress on brain function and metabolic adaptations. METHODS:Measurements at the start and finish lines included body weight, height, waist circumference, body fat, and a panel of hormones and biochemical markers. Post-race qEEG parameters were recorded under eyes-open (EO) and eyes-closed (EC) conditions. qEEG data were compared to a reference population (ages 6-90 years) and to an age-matched 27-year-old male medical student serving as a control subject. qEEG analysis evaluated voltage amplitudes, wave distribution patterns, theta-to-beta ratios (TBR), and coherence levels. Hormonal changes and oxidative stress markers were also assessed before and after race. RESULTS:Two rowers exhibited post-race dominance of high-frequency beta activity, while one displayed co-dominance of delta and beta waves. Compared to the control subject (TBR = 1.25), the rowers' low TBRs (< 0.2) indicated high vigilance and low relaxation during EC conditions. Cortisol levels increased in all rowers and were associated with beta coherence >1 SD above the reference mean. Testosterone decreased in two rowers but increased in one; the smallest cortisol increase corresponded with the largest testosterone decrement. Decreases in oxidative stress markers correlated with a shift from right- to left-sided alpha asymmetry, consistent with redistribution of alpha wave energy to the nondominant hemisphere. This pattern was also observed in the control subject. Increased testosterone in one rower was linked to a decrease in the percentage of sites exhibiting normal theta frequencies, indicating a potential role for testosterone in brain energy reallocation. CONCLUSION:The findings suggest that qEEG measurements reflect physiological adaptations in response to extreme stress, supporting the hypothesis that metabolic energy is reallocated to optimize vigilance and performance. The observed correlations between hormonal changes, oxidative stress markers, and qEEG parameters provide preliminary evidence of mechanisms for brain energy reallocation. These insights highlight the potential for qEEG to identify biomarkers of stress adaptation and lay the groundwork for larger studies to further elucidate these mechanisms.

The diversity of human mortuary practices and treatments in prehistory is widely recognised, but our understanding of the purpose and manner of corpse manipulation in many regions is limited. This article reports on unusual aspects of funerary archaeology at the Neolithic site of Dingsishan, southern China. Anatomical consideration of cutmarks on human bones and the positioning of bodies and body parts within burials suggests that mortuary treatments at this site included strategic and systematic disarticulation, evisceration and excarnation. Rather than signalling social differences, these practices may have resulted from the very practical need to save space.

The evolution of the medial longitudinal arch (MLA) is one of the most impactful adaptations in the hominin foot that emerged with bipedalism. When and how it evolved in the human lineage is still unresolved. Complicating the issue, clinical definitions of flatfoot in living Homo sapiens have not reached a consensus. Here we digitally investigate the navicular morphology of H. sapiens (living, archaeological, and fossil), great apes, and fossil hominins and its correlation with the MLA. A distinctive navicular shape characterises living H. sapiens with adult acquired flexible flatfoot, while the congenital flexible flatfoot exhibits a ‘normal’ navicular shape. All H. sapiens groups differentiate from great apes independently from variations in the MLA, likely because of bipedalism. Most australopith, H. naledi , and H. floresiensis navicular shapes are closer to those of great apes, which is inconsistent with a human-like MLA and instead might suggest a certain degree of arboreality. Navicular shape of OH 8 and fossil H. sapiens falls within the normal living H. sapiens spectrum of variation of the MLA (including congenital flexible flatfoot and individuals with a well-developed MLA). At the same time, H. neanderthalensis seem to be characterised by a different expression of the MLA.

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 different functions when energetically stressed. However, despite the central role played by the brain in both hominin evolution and metabolic budgeting, cognitive plasticity during energetic deficit remains unstudied. MATERIALS We considered human cognitive plasticity under conditions of energetic deficit by evaluating variability in performance in three key cognitive domains. To achieve this, cognitive performance in a sample of 48 athletes (m = 29, f = 19) was assessed before and after competing in multiday ultramarathons. RESULTS We demonstrate that under conditions of energetic deficit, performance in tasks of spatial working memory (which assessed ability to store location information, promoting landscape navigation and facilitating resource location and calorie acquisition) increased. In contrast, psychomotor speed (reaction time) remained unchanged and episodic memory performance (ability to recall information about specific events) decreased. DISCUSSION We propose that prioritization of spatial working memory performance during conditions of negative energy balance represents an adaptive response due to its role in facilitating calorie acquisition. We discuss these results with reference to a human evolutionary trajectory centred around encephalisation. Encephalisation affords great plasticity, facilitating rapid responses tailored to specific environmental conditions, and allowing humans to increase their capabilities as a phenotypically plastic species.

Medieval hospitals were founded to provide charity, but poverty and infirmity were broad and socially determined categories and little is known about the residents of these institutions and the pathways that led them there. Combining skeletal, isotopic and genetic data, the authors weave a collective biography of individuals buried at the Hospital of St John the Evangelist, Cambridge. By starting with the physical remains, rather than historical expectations, they demonstrate the varied life courses of those who were ultimately buried in the hospital's cemetery, illustrating the diverse faces of medieval poverty and institutional notions of charity. The findings highlight the value of collective osteobiography when reconstructing the social landscapes of the past.

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 our adaptive capabilities as a phenotypically plastic species. In recent years, evolutionary biologists have begun recruiting athletes as study participants and using contemporary sports as a model for studying evolution. This approach, known as human athletic palaeobiology, has identified ultra-endurance events as a valuable experimental model to investigate patterns of energy allocation during conditions of elevated energy demand, which are generally accompanied by an energy deficit. This energetic stress provokes detectable functional trade-offs in energy allocation between physiological processes. Early results from this modelsuggest thatlimited resources are preferentially allocated to processes which could be considered to confer the greatest immediate survival advantage (including immune and cognitive function). This aligns with evolutionary perspectives regarding energetic trade-offs during periods of acute and chronic energetic scarcity. Here, we discuss energy allocation patterns during periods of energetic stress as an area of shared interest between exercise physiology and evolutionary biology. We propose that, by addressing the ultimate "why" questions, namely why certain traits were selected for during the human evolutionary journey, an evolutionary perspective can complement the exercise physiology literature and provide a deeper insight of the reasons underpinning the body's physiological response to conditions of energetic stress.

A stable and consistent food source is one of the most important evolutionary challenges facing any species. Mammalian young are typically born incapable of provisioning for themselves, but all mammalian species, through the production of milk, have evolved a unique mechanism for transferring fat, proteins, sugar, as well as immunoglobins, hormones, and nutrients to their young, fueling neural development and growth throughout infancy. Milk is an essential resource for all growing mammals until they are physically able to forage and support themselves nutritionally. It has evolved as a means for mothers to synthesize food for their young, and to provide the intestinal bacteria to optimize an infant’s absorption of nutritional resources (Hinde and German, 2012). For the majority of human societies through time and space, the nutritional role of milk, like all mammals, is related to direct maternal–infant provisioning. While human hunter-gatherers typically do not consume non-human milk or dairy products, with the domestication of ruminant animals many human societies harnessed nonhuman sources of milk for the production of secondary dairy products such as cheese and yogurt, or for direct consumption (Roffet-Salque et al., 2018). While the transition to agriculture was variable in expression based on differences in local ecology and cultural history, the origin of farming and the domestication of plants and animals had a dramatic impact on the temporal and geographic patterning of milk production and consumption across the world (Stock et al., 2023). The transition from hunting and gathering to agricultural subsistence, often referred to as the “Neolithic Revolution,” is characterized by the development of human control over the reproduction of plants and animals, as well as their evolution through artificial selection. This involved a reduction in dietary breadth toward dependence on one or a few highly productive domesticated plants or animals, and has generally been associated with a greater proportion of dietary carbohydrates relative to protein and an increased prevalence of nutritional deficiencies (Cordain et al., 2000). The agricultural transition marks a significant change in human interaction with the natural world, where humans shifted from being predominantly influenced by natural environments to being the agents of environmental change in natural systems (Stephens et al., 2019). In this context, it is often viewed as the beginning of a series of changes in human social organization that directly result from the rise of food production and the storage of surpluses. These include sedentism, property ownership, social hierarchy, specialist craft production and related technological change, greater population density, and increased frequencies of infectious diseases and zoonotic diseases associated with domestic animals. Collectively, these changes have generally been seen This is an Open Access article distributed under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse, distribution, and reproduction in any medium, provided the original work is properly cited. © Stock, Wells Implications