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Myopia rates among Hadza hunter‐gatherers are low but not exceptional
Abstract
Objectives
Myopia rates are increasing globally. This epidemic is linked to increased school participation, decreased outdoor activity and the proliferation of near-work occupations. The Tanzanian Hadza have traditionally subsisted as hunter-gatherers. School participation has historically been low and near-work otherwise minimal. Previous studies have reported exceptionally low myopia rates among hunter-gatherers, though such studies are few. The present study aims to expand this dataset. We report Hadza myopia rates and compare them to those from other economic/subsistence niches. We look for temporal changes in eyesight, in line with changing Hadza subsistence. Further, we assess the impact two known myopia risk factors, gender and educational participation, on Hadza eyesight.
Materials and Methods
We measured visual acuity among 182 bush-living Hadza aged 10–75 using a non-Latin optotype. From these measures, we estimate age-specific myopia prevalences.
Results
We find age-specific myopia prevalences between 5% and 10% for individuals under 40, increasing thereafter. This is low compared to industrialized populations, although not atypical for rural and non-industrialized populations. Unlike previous studies of hunter-gatherers, myopia was not exceptionally rare. We find that Hadza men have better distance vision than Hadza women. Though the Hadza have experienced subsistence change, we find no statistical evidence of associated decreases in visual acuity between 2006 and 2013/14 after controlling for gender imbalances. Finally, we find no support for our prediction that schooling participation reduces visual acuity, though so few attended school (13 of 58) that this analysis lacked statistical power and probably represents a false negative.
Many have interpreted symbolic material culture in the deep past as evidencing the origins sophisticated, modern cognition. Scholars from across the behavioural and cognitive sciences, including linguists, psychologists, philosophers, neuroscientists, primatologists, archaeologists and paleoanthropologists have used such artefacts to assess the capacities of extinct human species, and to set benchmarks, milestones or otherwise chart the course of human cognitive evolution. To better calibrate our expectations, the present paper instead explores the material culture of three contemporary African forager groups. Results show that, while these groups are unequivocally behaviourally modern, they would leave scant long-lasting evidence of symbolic behaviour. Artefact-sets are typically small, perhaps as consequence of residential mobility. When excluding traded materials, few artefacts have components with moderate-strong taphonomic signatures. Present analyses show that artefact function influences preservation probability, such that utilitarian tools for the processing of materials and the preparation of food are disproportionately likely to contain archaeologically traceable components. There are substantial differences in material-use between populations, which create important population-level variation preservation probability independent of cognitive differences. I discuss the factors — cultural, ecological and practical — that influence material choice. In so doing, I highlight the difficulties of using past material culture as an evolutionary or cognitive yardstick.
Many researchers assume that until 10-12,000 years ago, humans lived in small, mobile, relatively egalitarian bands. This "nomadic-egalitarian model" suffuses the social sciences. It informs evolutionary explanations of behavior and our understanding of how contemporary societies differ from those of our evolutionary past. Here, we synthesize research challenging this model and articulate an alternative, the diverse Pleistocene model, to replace it. We review the limitations of using recent foragers as models of Late Pleistocene societies and the considerable social variation among foragers commonly considered small-scale, mobile, and egalitarian. We review ethnographic and archaeological findings covering 34 world regions showing that non-agricultural peoples often live in groups that are more sedentary, unequal, large, politically stratified, and capable of large-scale cooperation and resource management than is normally assumed. These characteristics are not restricted to extant Holocene hunter-gatherers but, as suggested by archaeological findings from 27 Middle Stone Age sites, likely characterized societies throughout the Late Pleistocene (until c. 130 ka), if not earlier. These findings have implications for how we understand human psychological adaptations and the broad trajectory of human history.
Humans’ willingness to bear costs to benefit others is an evolutionary puzzle. Cultural group selection proposes a possible answer to this puzzle—cooperative norms and institutions proliferate due to group-level benefits. For instance, belief in knowledgeable, moralizing deities is theorized to decrease selfishness and favoritism through threat of supernatural punishment. Similarly, norms of fairness and cooperation are theorized to have coevolved with engagement in markets, which necessitate anonymous exchanges. We investigate these theories among the Tanzanian Hadza who have historically had minimal exposure to markets or major world religions. Engagement with Western tourists, village markets, and Christian missionaries is increasingly leading researchers to ask how such interactions have affected cooperative behavior. We interviewed 172 Hadza from 15 camps varying in market proximity, and measured cooperative decision-making using economic games. We find that exposure to missionaries is associated with increased belief in a knowledgeable and punitive deity, with mixed evidence that these beliefs, in turn, affect game play. In contrast, we find some evidence that those living in market-adjacent regions exhibit less in-group favoritism when cooperating. These results support the claim that market-norms, and to some degree religious beliefs, facilitate greater cooperation and fairness in social interactions
Current criteria for amblyopia do not account for difference in visual acuity charts. This prospective observational study analyzed 100 children younger than 10 years treated at a tertiary referral center. Visual acuity was separately tested in each eye using Landolt C and tumbling E charts in a random order. For each chart, receiver operating characteristic curve analysis was performed to determine the best cutoff for visual acuity score. Main outcome measures included the difference in visual acuity scores between the two charts, the feasibility of repeated testing of visual acuity in each eye, and amblyopia cutoff values for each chart. Mean logMAR visual acuity scores obtained by tumbling E chart were significantly better than those obtained by Landolt C chart. For amblyopia, the best cutoff values were < + 0.14 (20/27 Snellen equivalent) for tumbling E chart and < + 0.24 (20/35 Snellen equivalent) for Landolt C chart. For children under 10 years old, visual acuity scores for tumbling E chart were significantly better than those for Landolt C chart. We suggest that amblyopia management in children should account for age and the type of visual acuity chart used.
The standard for measuring solar irradiance utilizes the units of watts per meter squared (W/m2). Irradiance meters are both costly and limited in the ability to measure low irradiance values. With a lower cost and higher sensitivity in low light conditions, light meters measure luminous flux per unit area (illuminance) utilizing the units of lumens per meter squared or lux (lx). An effective conversion factor between W/m2 and lx would enable the use of light meters to evaluate photovoltaic performance under low solar irradiance conditions. A survey of the literature found no definitive and readily available “rule of thumb” conversion standard between solar irradiance and illuminance. Easy-to-find Internet sources contain conflicting and widely varying values ranging from 688449 to 21000 lx for 1000 W/m2 (1 Sun) of solar irradiance. Peer-reviewed literature contains Luminous Efficacy equivalent values ranging from 21 to 131 lx per W/m2. This manuscript explores the relationship and establishes a theoretical and laboratory measurement guide for the conversion between solar irradiance and illuminance. The conversion factor includes standards data, equipment calibration accuracy, and uncertainty estimates. Solar Irradiance of 1 Sun (1000 W/m2) for an LED-based solar simulator is (116 ± 3) klx and (122 ± 1) klx for outdoor sunlight.
Introduction: We investigated the preliminary effects of dietary changes on the anthropometric measurements of child and adolescent Hadza foragers.
Methods: We conducted a cross‐sectional study comparing height and weight of participants (aged 0‐17 years) at two time points, 2005 (n = 195) and 2017 (n = 52), from two locations: semi‐nomadic “bush camps” and sedentary “village camps”. World Health Organization (WHO) calculators were used to generate standardized z‐scores for weight‐for‐height (WHZ), weight‐for‐age (WAZ), height‐for‐age (HAZ), and BMI‐for‐age (BMIFAZ). Cross tabulations were constructed for each measurement variable as a function of z‐score categories and the variables year, location, and sex.
Results: Residency in a village, and associated mixed‐subsistence diet, was associated with favorable growth, including greater WAZ (P < .001), HAZ (P < .001), and BMIFAZ (P = .004), but not WHZ (P = .717). Regardless of residency location, participants showed an improved WAZ (P = .021) and HAZ (P < .001) in the 2017 study year. We found no sex differences.
Discussion and Conclusion: These preliminary findings suggest that a mixed‐subsistence diet may confer advantages over an exclusive wild food diet, a trend also reported among other transitioning foragers.
The Hadza foragers of Tanzania are currently experiencing a nutritional shift that includes the intensification of domesticated cultigens in the diet. Despite these changes, no study, to date, has examined the possible effects of this transition on the food collection behavior of young foragers. Here we present a cross-sectional study on foraging behavior taken from two time points, 2005 and 2017. We compare the number of days foraged and the type and amount of food collected for young foragers, aged 5–14 years, in age- and season-matched samples. Compared with 2005, in 2017 fewer subadults left camp to forage, and overall, they targeted a smaller variety of wild foods, with the noticeable absence of wild honey, figs, and tubers. In addition, participants in 2017 were significantly more likely to have attended school. Despite the increased presence of domesticated plant foods in the diet and increased attendance at school, some young foragers continue to be highly productive in collecting wild, undomesticated foods. Despite the preliminary nature of our results, our findings suggest that the range of wild foods targeted by subadults is decreasing as the amount of domesticated cultigens in the diet increases. These data underscore the importance of studying diet composition and foraging decisions across temporal, nutritional, and ecological landscapes.
Objectives:
The incentives underlying men's hunting acquisition patterns among foragers are much debated. Some argue that hunters preferentially channel foods to their households, others maintain that foods are widely redistributed. Debates have focused on the redistribution of foods brought to camp, though the proper interpretation of results is contested. Here we instead address this question using two nutritional variables, employed as proxies for longer-term food access. We also report on broader patterns in nutritional status.
Materials and methods:
We measured male hunting success, hemoglobin concentration and body fatness among bush-living Hadza. Hunting success was measured using an aggregated reputation score. Hemoglobin concentration, a proxy for dietary red meat, was measured from fingerprick capillary blood. Body fatness, a proxy for energy balance, was measured using BMI and bioelectrical impedance.
Results:
We find no statistically significant relationship between a hunter's success and any measure of his nutritional status or that of his spouse. We further find that: women are, as elsewhere, at greater risk of iron-deficiency anemia than men; men had slightly lower BMIs than women; men but not women had significantly lower hemoglobin levels than in the 1960s.
Discussion:
The absence of an association between hunting reputation and nutritional status is consistent with generalized food sharing. Null results are difficult to interpret and findings could potentially be a consequence of insufficient signal in the study measures or some confounding effect. In any event, our results add to a substantial corpus of existing research that identifies few nutritional advantages to being or marrying a well-reputed Hadza hunter.
Background:
Due to high prevalence myopia has gained importance in epidemiological studies. Children with early onset are at particular risk of complications associated with myopia, as progression over time might result in high myopia and myopic macular degeneration. Both genetic and environmental factors play a role in the increasing prevalence of myopia. The aim of this study is to review the current literature on epidemiology and risk factors for myopia in school children (aged 6-19 years) around the world.
Main body:
PubMed and Medline were searched for the following keywords: prevalence, incidence, myopia, refractive error, risk factors, children and visual impairment. English language articles published between Jan 2013 and Mar 2019 were included in the study. Studies were critically reviewed for study methodology and robustness of data. Eighty studies were included in this literature review. Myopia prevalence remains higher in Asia (60%) compared with Europe (40%) using cycloplegic refraction examinations. Studies reporting on non-cycloplegic measurements show exceptionally high myopia prevalence rates in school children in East Asia (73%), and high rates in North America (42%). Low prevalence under 10% was described in African and South American children. In recent studies, risk factors for myopia in schoolchildren included low outdoor time and near work, dim light exposure, the use of LED lamps for homework, low sleeping hours, reading distance less than 25 cm and living in an urban environment.
Conclusion:
Low levels of outdoor activity and near work are well-established risk factors for myopia; this review provides evidence on additional environmental risk factors. New epidemiological studies should be carried out on implementation of public health strategies to tackle and avoid myopia. As the myopia prevalence rates in non-cycloplegic studies are overestimated, we recommend considering only cycloplegic measurements.
The ratio of index- and ring-finger lengths (2D:4D ratio) is thought to be related to prenatal androgen exposure, and in many, though not all, populations, men have a lower average digit ratio than do women. In many studies an inverse relationship has been observed, among both men and women, between 2D:4D ratio and measures of athletic ability. It has been further suggested that, in hunter-gatherer populations, 2D:4D ratio might also be negatively correlated with hunting ability, itself assumed to be contingent on athleticism. This hypothesis has been tested using endurance running performance among runners from a Western, educated, and industrialized population as a proximate measure of hunting ability. However, it has not previously been tested among actual hunter-gatherers using more ecologically valid measures of hunting ability and success. The current study addresses this question among Tanzanian Hadza hunter-gatherers. I employ a novel method of assessing hunting reputation that, unlike previous methods, allows granular distinctions to be made between hunters at all levels of perceived ability. I find no statistically significant relationship between digit ratio and either hunting reputation or two important hunting skills. I confirm that Hadza men have higher mean 2D:4D ratios than men in many Western populations. I discuss the notion that 2D:4D ratio may be the consequence of an allometric scaling relationship between relative and absolute finger lengths. Although it is difficult to draw clear conclusions from these results, the current study provides no support for the theorized relationship between 2D:4D ratio and hunting skill.
Objectives:
Congenital colour vision deficiency (CCVD) is an x-linked chromosome disorder that results from abnormalities in one or all three-cone type's photoreceptors. Early assessment and diagnosis of CCVD is necessary to minimise the disability associated with the condition. Multistage sampling was used to determine the prevalence of CCVD among Black South African school children in Durban, South Africa. The examination included visual acuity measurements, ocular motility evaluation, retinoscopy, auto-refraction, and examination of the anterior segment, media and fundus. Colour vision testing was performed using Colour Vision Testing Made Easy colour plates (Home Vision Care, Gulf Breeze, FL).
Results:
1305 (704 boys and 601 girls) Black school children participated in the study. The overall prevalence of colour vision deficiency was 29 (2.2%), which was higher in boys (25, 4.2%) than girls (4, 0.6%), with prevalence of protanopia and deuteranopia found to be 10 (0.7%) and 19 (1.5%), respectively. The prevalence of protanopia and deuteranopia among males was nine (1.5%) and 16 (2.7%) respectively, which was significantly higher than the 1 (0.1%) protanopia and 3 (0.4%) deuteranopia in females (p < 0.05). Policies and guidelines for comprehensive school eye health programmes which screen children for CCVD are required in South Africa.
Objective:
This nationwide population-based study aimed to examine the prospective association between near visual activities and incident myopia in Taiwanese children 7 to 12 years old over a 4-year follow-up period.
Design:
Prospective cohort design.
Participants:
There were 1958 children aged 7 to 12 years from the Taiwan 2009 National Health Interview Survey who were linked to the 2009 through 2013 claims data from the National Health Insurance system.
Methods:
Multivariable Cox proportional hazard models were used to estimate the associations between 3 types of near visual activities in sedentary posture, namely reading (< 0.5, 0.5-0.9, ≥1.0 hours per day [h/d]), use of computer, Internet, and games (<0.5, 0.5-0.9, ≥1.0 h/d), and "cram school" attendance (<0.5, 0.5-1.9, ≥2.0 h/d), and incident myopia.
Main outcome measures:
Prevalent myopia was defined as those who had ≥2 ambulatory care claims (International Classification of Diseases code 367.1) in 2008-2009. Incident myopia was defined by those who had at least 2 ambulatory care claims (International Classification of Diseases code 367.1) during the 4-year follow-up period (2010-2013) after excluding prevalent cases.
Results:
Overall, 26.8% of children had myopia at baseline, and 27.7% of those without myopia at baseline developed incident myopia between 2010 and 2013. On average, they spent 0.68±0.86 h/d on computer/Internet use, 0.63±0.67 h/d on reading, and 2.78±3.53 h/d on cram school. The results showed that children attending cram schools ≥2 h/d (hazard ratio, 1.31; 95% confidence interval, 1.03-1.68) had a higher risk of incident myopia. The effects of these activities remained similar in sensitivity analyses.
Conclusions:
Cram school attendance for ≥2 h/d may increase the risk of children's incident myopia. This effect may be due to increased near visual activity or reduced time outdoors.
Objectives
To determine whether more years spent in education is a causal risk factor for myopia, or whether myopia is a causal risk factor for more years in education.
Design
Bidirectional, two sample mendelian randomisation study.
Setting
Publically available genetic data from two consortiums applied to a large, independent population cohort. Genetic variants used as proxies for myopia and years of education were derived from two large genome wide association studies: 23andMe and Social Science Genetic Association Consortium (SSGAC), respectively.
Participants
67 798 men and women from England, Scotland, and Wales in the UK Biobank cohort with available information for years of completed education and refractive error.
Main outcome measures
Mendelian randomisation analyses were performed in two directions: the first exposure was the genetic predisposition to myopia, measured with 44 genetic variants strongly associated with myopia in 23andMe, and the outcome was years in education; and the second exposure was the genetic predisposition to higher levels of education, measured with 69 genetic variants from SSGAC, and the outcome was refractive error.
Results
Conventional regression analyses of the observational data suggested that every additional year of education was associated with a more myopic refractive error of −0.18 dioptres/y (95% confidence interval −0.19 to −0.17; P<2e-16). Mendelian randomisation analyses suggested the true causal effect was even stronger: −0.27 dioptres/y (−0.37 to −0.17; P=4e-8). By contrast, there was little evidence to suggest myopia affected education (years in education per dioptre of refractive error −0.008 y/dioptre, 95% confidence interval −0.041 to 0.025, P=0.6). Thus, the cumulative effect of more years in education on refractive error means that a university graduate from the United Kingdom with 17 years of education would, on average, be at least −1 dioptre more myopic than someone who left school at age 16 (with 12 years of education). Myopia of this magnitude would be sufficient to necessitate the use of glasses for driving. Sensitivity analyses showed minimal evidence for genetic confounding that could have biased the causal effect estimates.
Conclusions
This study shows that exposure to more years in education contributes to the rising prevalence of myopia. Increasing the length of time spent in education may inadvertently increase the prevalence of myopia and potential future visual disability.
Objective: This nationwide population-based study aimed to examine the prospective association between near visual activities and incident myopia in Taiwanese children aged 7-12 years old over a 4-year follow-up period.
Design: Prospective cohort design.
Participants: 1,958 children aged 7-12 years old from the Taiwan 2009 National Health Interview Survey, which were linked to the 2009-2013 claims data from the National Health Insurance system.
Methods: Multivariable Cox proportional hazard models were used to estimate the associations between three types of near visual activities, namely reading (< 0.5, 0.5-0.9, 1+ hour/day), use of computer, internet and games (< 0.5, 0.5-0.9, 1+ hour/day), and ‘cram school’ attendance (< 0.5, 0.5-2.0, 2.0+ hour/day), and incident myopia.
Main Outcome Measures: Prevalent myopia was defined as those who had at least 2 ambulatory care claims (International Classification of Diseases, [ICD] 367.1) in 2008-2009. Incident myopia was defined by those who had at least 2 ambulatory care claims (ICD 367.1) during the 4-year follow-up period (2010-2013) after excluding prevalent cases.
Results: Overall, 26.8% of children had myopia at baseline, while 27.7% of those without myopia at baseline developed incident myopia between 2010 and 2013. On average, they spent 0.68 (±0.86) hour/day on computer/internet use, 0.63 (±0.67) hour/day on reading and 2.78 (±3.53) hour/day on cram school. The results showed that children attending cram schools more than 2 hour/day (hazard ratio [HR] = 1.31; 95%CI: 1.03-1.68) had higher risk of incident myopia. The effects of these activities remained similar in sensitivity analyses.
Conclusions: Cram school attendance more than 2 hour/day may increase the risk of children’s incident myopia. This may be due to increased near visual activity or reduced time outdoors.
Purpose:
The aim of this study was to establish the frequency of refractive errors in children and adolescents aged between 8 and 17 years old, living in the metropolitan area of Bucaramanga (Colombia).
Methods:
This study was a secondary analysis of two descriptive cross-sectional studies that applied sociodemographic surveys and assessed visual acuity and refraction. Ametropias were classified as myopic errors, hyperopic errors, and mixed astigmatism. Eyes were considered emmetropic if none of these classifications were made. The data were collated using free software and analyzed with STATA/IC 11.2.
Results:
One thousand two hundred twenty-eight individuals were included in this study. Girls showed a higher rate of ametropia than boys. Hyperopic refractive errors were present in 23.1% of the subjects, and myopic errors in 11.2%. Only 0.2% of the eyes had high myopia (≤-6.00 D). Mixed astigmatism and anisometropia were uncommon, and myopia frequency increased with age. There were statistically significant steeper keratometric readings in myopic compared to hyperopic eyes.
Conclusions:
The frequency of refractive errors that we found of 36.7% is moderate compared to the global data. The rates and parameters statistically differed by sex and age groups. Our findings are useful for establishing refractive error rate benchmarks in low-middle-income countries and as a baseline for following their variation by sociodemographic factors.
Significance:
This study focused on a cohort that has not been studied and who currently have limited access to eye care services. The findings, while improving the understanding of the distribution of refractive errors, also enabled identification of children requiring intervention and provided a guide for future resource allocation.
Purpose:
The aim of conducting the study was to determine the prevalence and distribution of refractive error and its association with gender, age, and school grade level.
Methods:
Using a multistage random cluster sampling, 1586 children, 632 males (40%) and 954 females (60%), were selected. Their ages ranged between 13 and 18 years with a mean of 15.81 ± 1.56 years. The visual functions evaluated included visual acuity using the logarithm of minimum angle of resolution chart and refractive error measured using the autorefractor and then refined subjectively. Axis astigmatism was presented in the vector method where positive values of J0 indicated with-the-rule astigmatism, negative values indicated against-the-rule astigmatism, whereas J45 represented oblique astigmatism.
Results:
Overall, patients were myopic with a mean spherical power for right eye of -0.02 ± 0.47; mean astigmatic cylinder power was -0.09 ± 0.27 with mainly with-the-rule astigmatism (J0 = 0.01 ± 0.11). The prevalence estimates were as follows: myopia (at least -0.50) 7% (95% confidence interval [CI], 6 to 9%), hyperopia (at least 0.5) 5% (95% CI, 4 to 6%), astigmatism (at least -0.75 cylinder) 3% (95% CI, 2 to 4%), and anisometropia 3% (95% CI, 2 to 4%). There was no significant association between refractive error and any of the categories (gender, age, and grade levels).
Conclusions:
The prevalence of refractive error in the sample of high school children was relatively low. Myopia was the most prevalent, and findings on its association with age suggest that the prevalence of myopia may be stabilizing at late teenage years.
The brms package implements Bayesian multilevel models in R using the probabilistic programming language Stan. A wide range of distributions and link functions are supported, allowing users to fit – among others – linear, robust linear, binomial, Poisson, survival, ordinal, zero-inflated, hurdle, and even non-linear models all in a multilevel context. Further modeling options include autocorrelation of the response variable, user defined covariance structures, censored data, as well as meta-analytic standard errors. Prior specifications are flexible and explicitly encourage users to apply prior distributions that actually reflect their beliefs. In addition, model fit can easily be assessed and compared with the Watanabe-Akaike information criterion and leave-one-out cross-validation.
In our empirical and theoretical study of color naming among the Hadza, a Tanzanian hunter-gatherer group, we show that Hadza color naming is sparse (the color appearance of many stimulus tiles was not named), diverse (there was little consensus in the terms for the color appearance of most tiles), and distributed (the universal color categories of world languages are revealed in nascent form within the Hadza language community, when we analyze the patterns of how individual Hadza deploy color terms). Using our Hadza data set, Witzel shows an association between two measures of color naming performance and the chroma of the stimuli. His prediction of which colored tiles will be named with what level of consensus, while interesting, does not alter the validity of our conclusions.
Many researchers believe that the concept of adaptation is useful for understanding the human mind and human behavior.1-7 These researchers agree that adaptations are design features of organisms that evolved because they enhanced fitness in ancestral environments. They see the psychological mechanisms that make up the human mind as evolved adaptations. Further they are convinced that these adaptations are more likely to produce adaptive effects in environments similar to ancestral ones. In other words, the more similar the present environment to the ancestral one, the more likely the adaptation is to confer the reproductive advantage that led to its evolution. On the other hand, adaptations are less likely to confer an adaptive advantage in novel environments.
Despite these shared views, the question of exactly how to characterize these expectations has led to a major disagreement among researchers who study human behavior and psychology from an evolutionary perspective. One group, whose members label themselves evolutionary psychologists, has dealt with this problem by elaborating the concept of the environment of evolutionary adaptedness, (EEA).8-9 Other researchers, who are variously labeled behavioral ecologists, evolutionary ecologists, sociobiologists, or human paleontologists, have tended to question the value of this concept.10-14
In this paper, I review and critique the concept of the EEA and the associated evolutionary psychological view that the human mind consists of many specific-purpose decision-making mechanisms rather than just a few general-purpose ones. I then suggest an alternative to the EEA concept that I believe will serve better the purpose of modeling the relationship between adaptations and environments. I see this concept as a more logical complement than the EEA to the view that the human mind consists of many specific mechanisms. I refer to this new concept as the adaptively relevant environment (ARE). The expression "relevant environment" may also serve as a shorter label. The key idea motivating the ARE concept is that an organism consist of a large number of special-purpose adaptations, each interacting with only a part of the organism's environment. Thus, when a particular element of an environment changes, it is likely to affect some adaptations but not others. Logically, this idea is closely related to the idea that evolutionary change is mosaic: In the course of evolutionary change, some aspects of organisms change while others remain the same. In order to understand an adaptation fully at the proximate level, we need to study its design, the structure of its relevant environment, and the interaction of the two.
Before proceeding, a word of caution is necessary regarding the label evolutionary psychology. The label has both a broad and a narrow meaning. In its narrow meaning, it refers to the research program of scholars such as Barkow, Cosmides, Symons, and Tooby who rely heavily on the EEA and associated concepts and who insist that others who do not share this emphasis are not strict Darwinians or true adaptationists.2 However, many writers use the terms in a broader sense that includes all recent attempts to study human behavior and psychology in evolutionary terms. Robert Wright's recent book, The Moral Animal,15 uses the word in this broader sense.
Purpose:
Myopia is a common cause of vision loss, with uncorrected myopia the leading cause of distance vision impairment globally. Individual studies show variations in the prevalence of myopia and high myopia between regions and ethnic groups, and there continues to be uncertainty regarding increasing prevalence of myopia.
Design:
Systematic review and meta-analysis.
Methods:
We performed a systematic review and meta-analysis of the prevalence of myopia and high myopia and estimated temporal trends from 2000 to 2050 using data published since 1995. The primary data were gathered into 5-year age groups from 0 to ≥100, in urban or rural populations in each country, standardized to definitions of myopia of -0.50 diopter (D) or less and of high myopia of -5.00 D or less, projected to the year 2010, then meta-analyzed within Global Burden of Disease (GBD) regions. Any urban or rural age group that lacked data in a GBD region took data from the most similar region. The prevalence data were combined with urbanization data and population data from United Nations Population Department (UNPD) to estimate the prevalence of myopia and high myopia in each country of the world. These estimates were combined with myopia change estimates over time derived from regression analysis of published evidence to project to each decade from 2000 through 2050.
Results:
We included data from 145 studies covering 2.1 million participants. We estimated 1406 million people with myopia (22.9% of the world population; 95% confidence interval [CI], 932-1932 million [15.2%-31.5%]) and 163 million people with high myopia (2.7% of the world population; 95% CI, 86-387 million [1.4%-6.3%]) in 2000. We predict by 2050 there will be 4758 million people with myopia (49.8% of the world population; 3620-6056 million [95% CI, 43.4%-55.7%]) and 938 million people with high myopia (9.8% of the world population; 479-2104 million [95% CI, 5.7%-19.4%]).
Conclusions:
Myopia and high myopia estimates from 2000 to 2050 suggest significant increases in prevalences globally, with implications for planning services, including managing and preventing myopia-related ocular complications and vision loss among almost 1 billion people with high myopia.
OBJECTIVE:To determine six-year spherical refractive error change among white children and young adults in the UK and evaluate differences in refractive profiles between contemporary Australian children and historical UK data. DESIGN:Population-based prospective study. PARTICIPANTS:The Northern Ireland Childhood Errors of Refraction (NICER) study Phase 1 examined 1068 children in two cohorts aged 6-7 years and 12-13 years. Prospective data for six-year follow-up (Phase 3) are available for 212 12-13 year olds and 226 18-20 year olds in each cohort respectively. METHODS:Cycloplegic refractive error was determined using binocular open-field autorefraction (Shin-Nippon NVision-K 5001, cyclopentolate 1%). Participants were defined by spherical equivalent refraction (SER) as myopic SER ≤-0.50D, emmetropic -0.50D
Assess prevalence of myopia and identify associated risk factors in urban school children.
This was a cross-sectional study screening children for sub-normal vision and refractive errors in Delhi. Vision was tested by trained health workers using ETDRS charts. Risk factor questionnaire was filled for children with vision <6/9.5, wearing spectacles and for a subset (10%) of randomly selected children with normal vision. All children with vision <6/9.5 underwent cycloplegic refraction. The prevalence of myopia <-0.5 diopters was assessed. Association of risk factors and prevalence of myopia was analyzed for children with myopia and randomly selected non myopic children and adjusted odds ratio values for all risk factors were estimated.
A total number of 9884 children were screened with mean age of 11.6 + 2.2 years and 66.8% boys. Prevalence of myopia was 13.1% with only 320 children (24.7%) wearing appropriate spectacles. Mean myopic spherical error was -1.86 + 1.4 diopters. Prevalence of myopia was higher in private schools compared to government schools (p<0.001), in girls vs. boys (p = 0.004) and among older (> 11 years) children (p<0.001). There was a positive association of myopia with studying in private schools vs. government schools (p<0.001), positive family history (p< 0.001) and higher socio-economic status (p = 0.037). Positive association of presence of myopia was observed with children studying/reading > 5 hours per day (p < 0.001), watching television > 2 hours / day (p < 0.001) and with playing computer/video/mobile games (p < 0.001). An inverse association with outdoor activities/playing was observed with children playing > 2 hours in a day.
Myopia is a major health problem in Indian school children. It is important to identify modifiable risk factors associated with its development and try to develop cost effective intervention strategies.
The objective of this study is to review the association between ultraviolet (UV) light and ocular diseases. The data are sourced from the literature search of Medline up to Nov 2012, and the extracted data from original articles, review papers, and book chapters were reviewed. There is a strong evidence that ultraviolet radiation (UVR) exposure is associated with the formation of eyelid malignancies [basal cell carcinoma (BCC) and squamous cell carcinoma (SCC)], photokeratitis, climatic droplet keratopathy (CDK), pterygium, and cortical cataract. However, the evidence of the association between UV exposure and development of pinguecula, nuclear and posterior subcapsular cataract, ocular surface squamous neoplasia (OSSN), and ocular melanoma remained limited. There is insufficient evidence to determine whether age-related macular degeneration (AMD) is related to UV exposure. It is now suggested that AMD is probably related to visible radiation especially blue light, rather than UV exposure. From the results, it was concluded that eyelid malignancies (BCC and SCC), photokeratitis, CDK, pterygium, and cortical cataract are strongly associated with UVR exposure. Evidence of the association between UV exposure and development of pinguecula, nuclear and posterior subcapsular cataract, OSSN, and ocular melanoma remained limited. There is insufficient evidence to determine whether AMD is related to UV exposure. Simple behaviural changes, appropriate clothing, wearing hats, and UV blocking spectacles, sunglasses or contact lens are effective measures for UV protection.
Hunting is a characteristic feature of early human subsistence and many theories of evolution have emphasized the role of hunting in hominization. Still today hunting ability continues to be selected for in extant foragers with better hunters experiencing greater reproductive success. Yet little is known about the traits that comprise a successful hunter, traits that are presupposed to also be under selection. Two complementary empirical analyses were conducted to examine this question using data collected from Hadza hunter-gatherers in Tanzania. First, data on upper-body strength, running speed, target precision and visual and auditory acuity were collected to examine the traits that predict hunting reputation in men. Second, interview data were also collected from Hadza informants about the traits they deem important for hunting. Results from the first study implicate upper-body strength as the strongest and most consistent predictor of men’s hunting reputation. Hadza conventional wisdom also accord with these findings. Although informants stressed the importance of non-physical traits, such as “intelligence” and “heart”, strong arms were cited as the most important physical trait for hunting. Finally, men with stronger upper-bodies experienced greater reproductive success, a result that is largely mediated by hunting reputation. These findings suggest that selection for hunting ability may have acted on men’s upper-bodies. Nevertheless, the importance of effort on strength and hunting success cannot be dismissed. This is also discussed.
Purpose:
To determine the differences in prevalence rates of refractive errors in young Singaporean males over a 13-year period between 1996-1997 and 2009-2010 METHODS: Non-cycloplegic autorefraction data were obtained in a survey of 15,085 young male subjects (mean age 19.5 ± 1.4 years, range 16-25 years) in 1996-1997 using a Nikon NRK-8000 autorefractor. A second survey of 28,908 male subjects (mean age 19.8 ± 1.2 years, range 17-29 years) was conducted in 2009-2010 using a Huvitz MRK-3100 autorefractor.
Results:
The overall prevalence of myopia (spherical equivalent, SEq, worse than -0.5 diopters, D) was similar in 2009-2010 (81.6%) and 1996-1997 (79.2%; odds ratio 1.38, 95% confidence interval 1.31-1.46; p < 0.001). The prevalence of high myopia (SEq worse than -6.0D) increased from 13.1% in 1996-1997 to 14.7% in 2009-2010 (p < 0.001). The prevalence of refractive astigmatism increased significantly from 41.4% in 1996-1997 to 50.9% in 2009-2010 (p < 0.001).
Conclusions:
Our results show that the prevalence of myopia and high myopia remained high and the prevalence of astigmatism increased in young male adults in Singapore over a 13-year period after controlling for age, education and ethnicity.
This review aims at elucidating the interaction between genetic and environmental factors in the aetiology of primarily low myopia. Genetics greatly influence the growth of the eye, but the fine correlation between the components of refraction for the eye to become emmetrope is affected by environmental factors such as education, metabolism, physical activity, and outdoor activity.Eye advance online publication, 20 December 2013; doi:10.1038/eye.2013.254.
Over the last half century, anthropologists have vigorously debated the adaptive motivations underlying food acquisition choices and food-sharing among hunter-gatherer groups. Numerous explanations have been proposed to account for high-levels of generosity in food-sharing, including self- and family-provisioning, reciprocity, tolerated theft and pro-social- or skill-signaling. However, few studies have asked foragers directly and systematically about the motivations underlying their foraging and sharing decisions. We recruited 110 Hadza participants and employed a combination of free-response, yes/no, ranking and forced-choice questions to do just this. In free-response answers, respondents typically gave outcome-oriented accounts of foraging motive (e.g., to get food) and moralistic accounts of sharing motive (e.g., I have a good heart). In ranking tasks, participants gave precedence to reciprocity as a motive for sharing food beyond the household. We found small but clear gender differences in foraging motive, in line with previous predictions: women were more likely than men to rank family-provisioning highly whereas men were more likely than women to rank skill-signaling highly. However, despite these gender differences, the relative importance of different motivations was similar across genders and skill-signaling, sharing and family-provisioning were the most important motivators of foraging activity for both men and women. Contrary to the expectations of tolerated theft, peer complaints and requests for food ranked very low. There are several compelling reasons that evolutionary thinkers, typically interested in ultimate-level adaptive processes, have traditionally eschewed direct and explicit investigations of motive. However, these data may yet provide important insights.
In the nineteenth century, the prevalence of myopia began to rise, and Cohn stressed the role of education. Later, based on twin studies, Sorsby argued that refraction was almost totally genetically determined. This became the dominant view. However, rapid increases in the prevalence of myopia were then reported, especially in East and Southeast Asia, where the prevalence of myopia in children completing secondary school is now 80–90 per cent, with around 20 per cent highly myopic, and at risk of ocular pathology. It is not possible to explain these rapid changes genetically, since gene pools cannot change that fast. Nevertheless, there are at least 200 genetic forms of myopia, but these account for myopia in only a low percentage of the population. Genome‐wide association studies have identified over 150 single‐nucleotide polymorphisms (SNPs) associated with myopia, but they account for < 10 per cent of the variation in refraction. In contrast, twin studies have given consistently high heritability estimates for myopia. The high twin study heritability may be explained by the limited environmental variation within twin pairs, combined with basic assumptions made in twin studies. The SNP‐heritability approach suggests that 25–35 per cent of the variation may be accounted for by hundreds or even thousands of SNPs. The apparent conflicts in the literature can be explained by the aetiological heterogeneity of myopia, and the fact that estimates of heritability are population‐specific. It has been proposed that environmental variation is more relevant to variations between populations; however, the current differences between populations are due to changes within populations, driven by educational pressures, and limited time spent outdoors. Ethnic differences in myopia and the effects of parental myopia now seem more likely to be explained by environmental influences. Genetic studies have not yet defined molecular pathways and preventive interventions, and the predictive power of current genetic data is limited.
The measurement of hunting ability has been central to several debates about the goals of men's hunting among the Hadza and other hunter-gatherer populations. Hunting ability has previously been measured indirectly, by weighing the amount of food individuals bring back to camp over an extended period, their central place hunting return rate, and by conducting hunting ability interviews. Despite the centrality of the hunting ability concept, some authors (Hill & Kintigh, 2009) have expressed scepticism that such measures accurately capture individual differences in actual hunting ability. In the current study, we introduce a novel measure of hunting reputation which, unlike previous ones, allows fine-grained distinction between hunters of all reputations. To assess the suitability of this measure as a viable proxy for hunting ability, we address two further questions. First, to what extent do interviewees agree about the hunting ability of their present and former campmates? Second, to what extent does this measure of hunting reputation reflect success in four tasks expected to capture important components of hunting ability? We demonstrate that these measures of hunting reputation appear to reflect variation in these skills. We argue, however, that hunting reputation appears too noisy an index of these skills and, we infer, hunting ability in general for hunting to act, as some have suggested (e.g. Hawkes & Bird, 2002), as an honest signal of cryptic qualities related to hunting ability.
Background
To investigate the relationship between dietary intakes at six, nine and 12 months and risk of myopia in three‐year‐old children in a birth cohort.
Methods
Three hundred and seventeen children from the Growing Up in Singapore Towards Healthy Outcomes (GUSTO) study were included. Dietary intake at six, nine and 12 months of age was ascertained using either 24‐hour recalls or three‐day food diaries completed by parents. Cycloplegia was achieved with three drops of one per cent cycloplentolate instilled at five minute intervals. Cycloplegic autorefraction and axial length (AL) were measured at three years of age with a table‐mounted autorefractor and optical biometer, respectively. Myopia was defined as spherical equivalent (SE) of ≤ −0.50 D. Associations of dietary intake with SE, AL and myopia were examined by single dietary factor models using two multivariable regression models. Model 1 included adjusting for age, gender and total energy intake. Model 2 included additional adjustments for ethnicity, time spent outdoors, maternal education and parental myopia.
Results
In the single dietary factor adjusted models, dietary intakes at six, nine and 12 months were not associated with SE, AL and myopia. In model 1, protein, fat and carbohydrate intakes were not associated with SE, AL and myopia at any of the three time points (p > 0.05). In model 2, protein, fat and carbohydrate intakes were not associated with SE, AL and myopia at any of the three time points (p > 0.05).
Conclusions
In this study, there was no evidence that diet at ages six, nine and 12 months was related to SE, AL or myopia at age three years. Further prospective studies with larger sample sizes are needed to understand the influence of diet on eye development in young children.
Purpose: We aim to determine the association of the types of lamp for homework including incandescent lamp, fluorescent lamp, and light-emitting diode (LED) lamp with the prevalence of myopia in Chinese children.
Methods: 2346 grade 7 students from ten middle schools (93.5% response rate) aged 13 to 14 years in Mojiang, a small county located in Southwestern China, participated in the study. Refractive error was measured with cycloplegia using an autorefractor by optometrists or trained technicians. An IOL Master was used to measure ocular biometric parameters including axial length (AL). Information regarding the types of lamp for homework af``ter schools was collected by questionnaires.
Results: Of all the study participants, 693 (29.5%) were affected by myopia, with the prevalence estimates being higher in girls (36.8%; 95% confidence interval [CI]: 34.0, 39.6) than in boys (22.8%; 95% CI: 20.4, 25.1) (P < 0.001). After adjusting for potential confounders such as gender, height, parental history of myopia, time on computer use, time on watching TV, time outdoors, and time on reading and writing, participants using LED lamps for homework had a more myopic refractive error and a longer AL compared with those using incandescent or fluorescent lamps. There were no significant differences in myopia prevalence between children using incandescent and fluorescent lamps for homework. The population attributable risk percentage for myopia associated with using LED lamps for homework after schools was 11.2%.
Conclusions: Using LED lamps for homework after schools might contribute to the development of myopia among school-aged children.
There is an epidemic of myopia in East and Southeast Asia, with the prevalence of myopia in young adults around 80-90%, and an accompanying high prevalence of high myopia in young adults (10-20%). This may foreshadow an increase in low vision and blindness due to pathological myopia. These two epidemics are linked, since the increasingly early onset of myopia, combined with high progression rates, naturally generates an epidemic of high myopia, with high prevalences of "acquired" high myopia appearing around the age of 11-13. The major risk factors identified are intensive education, and limited time outdoors. The localization of the epidemic appears to be due to the high educational pressures and limited time outdoors in the region, rather than to genetically elevated sensitivity to these factors. Causality has been demonstrated in the case of time outdoors through randomized clinical trials in which increased time outdoors in schools has prevented the onset of myopia. In the case of educational pressures, evidence of causality comes from the high prevalence of myopia and high myopia in Jewish boys attending Orthodox schools in Israel compared to their sisters attending religious schools, and boys and girls attending secular schools. Combining increased time outdoors in schools, to slow the onset of myopia, with clinical methods for slowing myopic progression, should lead to the control of this epidemic, which would otherwise pose a major health challenge. Reforms to the organization of school systems to reduce intense early competition for accelerated learning pathways may also be important.
OBJECTIVE: To estimate the potential global economic productivity loss associated with the existing burden of visual impairment from uncorrected refractive error (URE). METHODS: Conservative assumptions and national population, epidemiological and economic data were used to estimate the purchasing power parity-adjusted gross domestic product (PPP-adjusted GDP) loss for all individuals with impaired vision and blindness, and for individuals with normal sight who provide them with informal care. FINDINGS: An estimated 158.1 million cases of visual impairment resulted from uncorrected or undercorrected refractive error in 2007; of these, 8.7 million were blind. We estimated the global economic productivity loss in international dollars (I 427.7 billion before, and I 121.4 billion. CONCLUSION: Even under the most conservative assumptions, the total estimated productivity loss, in 1000, a net economic gain may be attainable.
Diet composition and food choice are not only central to the daily lives of all living people, but are consistently linked with turning points in human evolutionary history. As such, scholars from a wide range of fields have taken great interest in the role that subsistence has played in both human cultural and biological evolution. Central to this discussion is the diet composition and nutrition of contemporary hunters and gatherers, who are frequently conscripted as model populations for ancestral human nutrition. Research among the world's few remaining foraging populations is experiencing a resurgence, as they are making the final transition away from diets composed of wild foods, to those dominated by domesticated cultigens and/or processed foods. In an effort to glean as much information as possible, before such populations are no longer hunting and gathering, researchers interested in the evolution of human nutrition are rapidly collecting and accessing new and more data. Methods of scientific inquiry are in the midst of rapid change and scholars are able to revisit long-standing questions using state of the art analyses. Here, using the most relevant findings from studies in ethnography, nutrition, human physiology, and microbiomes, we provide a brief summary of the study of the evolution of human nutrition as it has specifically pertained to data coming from living hunter-gatherers. In doing so, we hope to bridge the disciplines that are currently invested in research on nutrition and health among foraging populations.
Purpose:
To systematically review epidemiologic and laboratory studies on the etiology of high myopia and its links to pathologic myopia.
Methods:
Regular Medline searches have been performed for the past 20 years, using "myopia" as the basic search term. The abstracts of all articles have been scrutinized for relevance, and where necessary, translations of articles in languages other than English were obtained.
Results:
Systematic review shows that there is an epidemic of myopia and high myopia in young adults in East and Southeast Asia, with similar but smaller trends in other parts of the world. This suggests an impending epidemic of pathologic myopia. High myopia in young adults in East and Southeast Asia is now predominantly associated with environmental factors, rather than genetic background. Recent clinical trials show that the onset of myopia can be reduced by increasing the time children spend outdoors, and methods to slow the progression of myopia are now available.
Conclusion:
High myopia is now largely associated with environmental factors that have caused the epidemic of myopia in East and Southeast Asia. An important clinical question is whether the pathologic consequences of acquired high myopia are similar to those associated with classic genetic high myopia. Increased time outdoors can be used to slow the onset of myopia, whereas methods for slowing progression are now available clinically. These approaches should enable the current epidemics of myopia and high myopia to be turned around, preventing an explosion of pathologic myopia.
Evolutionary science is critical to an understanding of integrated human biology and is increasingly recognized as a core underpinning discipline by medical and public health professionals. Advances in the fields of genomics, epigenetics, developmental biology and epidemiology have led to the growing realization that incorporating evolutionary thinking is essential for medicine to achieve its full potential. This is the first integrated and comprehensive textbook to explain the principles of evolutionary biology from a medical perspective and to focus on how medicine and public health might utilize evolutionary biology. It is written in a style which is accessible to a broad range of readers, whether or not they have had formal exposure to evolutionary science. Principles of Evolutionary Medicine is divided into three sections: the first provides a systematic approach to the principles of evolutionary biology as they apply to human health and disease, using examples specifically relevant to medicine. It incorporates chapters on evolutionary processes, molecular evolution, the evolution of humans, life history theory, and evolutionary-developmental biology. The second part illustrates the application of these principles to our understanding of nutrition and metabolism, reproduction, combatting infectious disease and stress, and human behaviour. The final section provides a general framework to show in practical terms how the principles of evolutionary medicine can be applied in medical practice and public health.
The Hadza, an ethnic group indigenous to northern Tanzania, are one of the few remaining hunter-gatherer populations. Archaeology shows 130,000 years of hunting and gathering in their land but Hadza are rapidly losing areas vital to their way of life. This book offers a unique opportunity to capture a disappearing lifestyle. Blurton Jones interweaves data from ecology, demography and evolutionary ecology to present a comprehensive analysis of the Hadza foragers. Discussion centres on expansion of the adaptationist perspective beyond topics customarily studied in human behavioural ecology, to interpret a wider range of anthropological concepts. Analysing behavioural aspects, with a specific focus on relationships and their wider impact on the population, this book reports the demographic consequences of different patterns of marriage and the availability of helpers such as husbands, children, and grandmothers. Essential for researchers and graduate students alike, this book will challenge preconceptions of human sociobiology.
In The Hadza, Frank Marlowe provides a quantitative ethnography of one of the last remaining societies of hunter-gatherers in the world. The Hadza, who inhabit an area of East Africa near the Serengeti and Olduvai Gorge, have long drawn the attention of anthropologists and archaeologists for maintaining a foraging lifestyle in a region that is key to understanding human origins. Marlowe ably applies his years of research with the Hadza to cover the traditional topics in ethnography-subsistence, material culture, religion, and social structure. But the book's unique contribution is to introduce readers to the more contemporary field of behavioral ecology, which attempts to understand human behavior from an evolutionary perspective. To that end, The Hadza also articulates the necessary background for readers whose exposure to human evolutionary theory is minimal.
Background. A number of papers have reported an association between diet and myopia; however, these studies have generally considered the diet of children already myopic. This study compared the nutritional intake and some simple body measurements for a group of children who subsequently became myopic with that of a group who did not become myopic. Methods. The nutritional data for 24 subjects who developed myopia between the ages of 7 and 10 years were compared with data for 68 subjects who were still not myopic at the age of 10 years. Results. Children who developed myopia had a generally lower intake of many of the food components than children who did not become myopic. The differences were statistically significant for energy intake, protein, fat, vitamins B1, B2 and C, phosphorus, iron, and cholesterol. Despite these differences, children who became myopic were neither shorter nor lighter, at the age of 7 years, than children who did not become myopic. Conclusions. There is no evidence that the incident myopes were in any way undernourished and it therefore seems that their energy requirements were less than those of the control subjects.
PurposeTo determine the prevalence of myopia in school children in Greater Beijing.Methods
The Beijing Childhood Eye Study was a school-based cross-sectional study. One school of each level (primary, junior high, senior high) was randomly selected from nine randomly selected districts of Greater Beijing. The children underwent non-cycloplegic refractometry and their parents an interview.ResultsOf 16 771 eligible students, 15 066 (89.8%) children with a mean age of 13.2 ± 3.4 years (range: 7–18 years) participated. Prevalence of myopia defined as refractive error of ≤−0.50 diopters (D), ≤−1.00 D, ≤−6.00 D and ≤−8.00 D in the right eye was 64.9 ± 0.4%, 53.0 ± 0.4%, 4.3 ± 0.2% and 1.0 ± 0.1% respectively. In multivariate analysis, prevalence of myopia was significantly (p < 0.001) associated with higher age, female gender, urban region and school type. Prevalence of myopia of ≤−1.00 D and of ≤−8.0 D increased from 9.7% and 0% in 7 year olds, respectively, to 74.2% and 1.8% in 17- or 18 year olds respectively. The latter figure was already similar (p = 0.39) to the prevalence of high myopia in the elderly Beijing Eye Study population (1.6%). In a subset of 1082 children undergoing cycloplegia, difference in refractive error between prior to and after cycloplegia was 0.31 ± 0.47 diopters.Conclusions
On the basis of previous investigations from China, our study indicated an ongoing myopic shift in the young generation. Since the prevalence of high myopia in children aged 17 or 18 years was already similar to the one in the elderly Beijing population, the data prognosticate an increase in vision threatening high myopia in the future adult population.
The longstanding view that children among foraging populations are largely dependent on the food collection efforts of others is an assumed and implicit characteristic of several models of human life history and family formation. The evolution of protracted juvenility in humans is often explained using the “embodied capital model” which argues that prolonged investment in growth and delayed reproduction evolved because a long training period is required to learn difficult foraging tasks and become a self-sufficient forager. The model suggests that if juvenile investment in growth and learning yields an increase in adult productivity, then selection will favor delayed maturity, long life span, and increased brain size. Here, we test the embodied capital model with naturalistic foraging and consumption data among juvenile Hadza hunter–gatherers of Tanzania to determine the extent to which children self-provision. We found that sex had a significant effect on both the type and the amount of food brought back to camp and consumed while out foraging; compared to their male counterparts, young female foragers consumed less while foraging and returned to camp with more food. A wide variation in caloric returns was seen across all foragers in the sample. When analyzing only food brought back to camp, age was not a significant predictor. When combining the amount of food back to camp and the amount consumed while out foraging, however, older children consistently collected more food. The data presented here suggest that although older children do appear to have greater overall foraging success, even very young children are capable of collecting a considerable amount of food. Our data, although lending support to the embodied capital model, suggest that although foraging efficiency increases with age, it remains difficult to determine if this efficiency is a byproduct of learning, strength, or perhaps individual motivation. In addition, our results indicate that juvenile self-provisioning may have played a key role in the evolution of food sharing and cooperation during hominin evolution.
To assess the prevalence and risk factors of myopia in 19-year-old males in Jeju, a rural area of Korea Methods: A total of 2,805 subjects were included. Refractive examination was performed with cycloplegia to test for myopia (< -0.5 diopters [D]), and high myopia (< -6.0 D). Possible associated factors were evaluated including height, weight, educational level, color vision deficiency. Results: The prevalences of myopia and high myopia were 83.3% and 6.8%, respectively, in 19-year-old males in Jeju. University students in their fourth to sixth years showed a higher risk for myopia (odds ratio [OR] 2.04; 95% confidence interval [CI], 1.52 - 2.71, P < 0.001) than those with lower academic achievement.
The prevalence of myopia was relatively high (83.3%) in a rural area of Korea, while the rate of high myopia was relatively low (6.8%) compared with that (20.6%) in urban area of Korea.
Purpose:
To examine the risk factors for incident myopia in Australian schoolchildren.
Design:
Population-based, longitudinal cohort study.
Participants:
The Sydney Adolescent Vascular and Eye Study (SAVES) was a 5- to 6-year follow-up of the Sydney Myopia Study (SMS). At follow-up, 2103 children were reexamined: 892 (50.5%) from the younger cohort and 1211 (51.5%) from the older cohort. Of these, 863 in the younger cohort and 1196 in the older cohort had complete refraction data.
Methods:
Cycloplegic autorefraction (cyclopentolate 1%; Canon RK-F1; Canon, Tokyo, Japan) was measured at baseline and follow-up. Myopia was defined as a spherical equivalent refraction of ≤-0.50 diopters (D). Children were classified as having incident myopia if they were nonmyopic at baseline and myopic in either eye at follow-up. A comprehensive questionnaire determined the amount of time children spent outdoors and doing near work per week at baseline, as well as ethnicity, parental myopia, and socioeconomic status.
Main outcome measures:
Incident myopia.
Results:
Children who became myopic spent less time outdoors compared with children who remained nonmyopic (younger cohort, 16.3 vs. 21.0 hours, respectively, P<0.0001; older cohort, 17.2 vs. 19.6 hours, respectively, P=0.001). Children who became myopic performed significantly more near work (19.4 vs. 17.6 hours; P=0.02) in the younger cohort, but not in the older cohort (P=0.06). Children with 1 or 2 parents who were myopic had greater odds of incident myopia (1 parent: odds ratio [OR], 3.2, 95% confidence interval [CI], 1.9-5.2; both parents: OR, 3.3, 95% CI, 1.6-6.8) in the younger but not the older cohort. Children of East Asian ethnicity had a higher incidence of myopia compared with children of European Caucasian ethnicity (both P<0.0001) and spent less time outdoors (both P<0.0001). A less hyperopic refraction at baseline was the most significant predictor of incident myopia. The addition of time outdoors, near work, parental myopia, and ethnicity to the model significantly improved the predictive power (P<0.0001) in the younger cohort but had little effect in the older cohort.
Conclusions:
Time spent outdoors was negatively associated with incident myopia in both age cohorts. Near work and parental myopia were additional significant risk factors for myopia only in the younger cohort.
Financial disclosure(s):
The author(s) have no proprietary or commercial interest in any materials discussed in this article.