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![Large adult brain mass and EQ are favored by environmental difficulty, moderate skill effectiveness, and costly memory. Plots are the predicted adult body and brain mass, EQ, and skill vs. parameter values with exponential competence. A-C show adult body mass (blue) and adult brain mass (red). D-F show adult EQ (green) and skill (orange). Vertical axes are in different scales. Dashed horizontal lines are the observed values in human females [69].](publication/301800067/figure/fig3/AS:620105520123905@1524856085287/Large-adult-brain-mass-and-EQ-are-favored-by-environmental-difficulty-moderate-skill.png)
Large adult brain mass and EQ are favored by environmental difficulty, moderate skill effectiveness, and costly memory. Plots are the predicted adult body and brain mass, EQ, and skill vs. parameter values with exponential competence. A-C show adult body mass (blue) and adult brain mass (red). D-F show adult EQ (green) and skill (orange). Vertical axes are in different scales. Dashed horizontal lines are the observed values in human females [69].
Source publication
Mathematical modeling of brain evolution is scarce, possibly due in part to the difficulty of describing how brain relates to fitness. Yet such modeling is needed to formalize verbal arguments and deepen our understanding of brain evolution. To address this issue, we combine elements of life history and metabolic theories to formulate a metabolical...
Contexts in source publication
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... on first encounter, the finding that moderately effective skills are 571 most conducive to a large brain and high skill is a consequence of the need of more skills 572 when their effectiveness decreases (Fig. 4B). Regarding memory cost, the strong effect 573 of memory cost on favoring a high EQ at first glance suggests that a larger EQ than the 574 observed in humans is possible if memory were costlier (see dashed lines in Fig. ...
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... on first encounter, the finding that moderately effective skills are 571 most conducive to a large brain and high skill is a consequence of the need of more skills 572 when their effectiveness decreases (Fig. 4B). Regarding memory cost, the strong effect 573 of memory cost on favoring a high EQ at first glance suggests that a larger EQ than the 574 observed in humans is possible if memory were costlier (see dashed lines in Fig. ...
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... now vary parameter values to assess what factors favor a large brain at 465 adulthood in a me-against-nature setting. with exceedingly challenging environments, the individual is favored to reproduce early 475 without substantial body or brain growth because it fails to gain enough skills to 476 maintain its body mass as (allo)parental care decreases with age (Fig. S13). with skill effectiveness (Fig. 4B). Hence, adult brain mass is largest with moderately 493 effective ...
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... larger brain is also favored by skills that are increasingly expensive for the brain 495 to maintain (costly memory, increasing B k ), but exceedingly costly memory prevents 496 body and brain growth (Fig. 4C). Costly memory favors a large brain because then a 497 larger brain mass is required to energetically support skill growth [Eq. (14)]. If 498 memory is exceedingly costly, skills fail to grow and energy extraction is unsuccessful, 499 causing the individual to reproduce without substantial growth (Fig. ...
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... larger brain is also favored by skills that are increasingly expensive for the brain 495 to maintain (costly memory, increasing B k ), but exceedingly costly memory prevents 496 body and brain growth (Fig. 4C). Costly memory favors a large brain because then a 497 larger brain mass is required to energetically support skill growth [Eq. (14)]. If 498 memory is exceedingly costly, skills fail to grow and energy extraction is unsuccessful, 499 causing the individual to reproduce without substantial growth (Fig. ...
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... brain growth patterns are also qualitatively similar but quantitatively 417 different with power and exponential competence (Fig. 2D,H). Adult brain mass is 418 predicted to be larger with competence as an exponential rather than as a power 419 function (Fig. 2D,H). As for body mass, our exploration of the parameter space 420 indicates that the larger brain mass with exponential competence is robust to parameter 421 change (Figs. 4A-C, S16A-C, S17A-F). Moreover, the encephalization quotient (EQ, 422 which is the ratio of observed adult brain mass over expected adult brain mass for a 423 given body mass) is also larger with exponential competence for the benchmark 424 parameter values (Table 1). For illustration, with competence as a power function, the 425 predicted adult body and brain mass approach those observed in late H. erectus ( Fig. 426 2B,D). In contrast, with competence as an exponential function, the predicted adult 427 body and brain mass approach those of Neanderthals (Fig. 2F,H). The larger EQ with 428 exponential competence is also robust to parameter change (Figs. 4D-F
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... favoring a large EQ and high skill 501 A large EQ and high adult skill number are generally favored by the same factors that 502 favor a large adult brain. However, the memory cost has a particularly strong effect 503 favoring a large EQ because it simultaneously favors increased brain and reduced body 504 mass (Fig. 4C,F). In contrast to its effect on EQ, increasing memory cost disfavors a 505 high adult skill number (Fig. 4F). That is, a higher EQ attained by increasing memory 506 costs is accompained by a decrease in skill number (Fig. 4C,F). The factors that favor a 507 large brain, large EQ, and high skill are similar with either power or exponential 508 competence (Fig. 4 and Figs. S16, S17). Importantly, although with the estimated 509 parameter values the me-against-nature setting can recover human growth patterns 510 yielding adult body and brain mass of ancient humans, our exploration of the 511 parameters that were not estimated from data suggests that the me-against-nature 512 setting cannot recover human growth patterns yielding adult body and brain mass of 513 modern ...
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... favoring a large EQ and high skill 501 A large EQ and high adult skill number are generally favored by the same factors that 502 favor a large adult brain. However, the memory cost has a particularly strong effect 503 favoring a large EQ because it simultaneously favors increased brain and reduced body 504 mass (Fig. 4C,F). In contrast to its effect on EQ, increasing memory cost disfavors a 505 high adult skill number (Fig. 4F). That is, a higher EQ attained by increasing memory 506 costs is accompained by a decrease in skill number (Fig. 4C,F). The factors that favor a 507 large brain, large EQ, and high skill are similar with either power or exponential 508 competence (Fig. 4 and Figs. S16, S17). Importantly, although with the estimated 509 parameter values the me-against-nature setting can recover human growth patterns 510 yielding adult body and brain mass of ancient humans, our exploration of the 511 parameters that were not estimated from data suggests that the me-against-nature 512 setting cannot recover human growth patterns yielding adult body and brain mass of 513 modern ...
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... favoring a large EQ and high skill 501 A large EQ and high adult skill number are generally favored by the same factors that 502 favor a large adult brain. However, the memory cost has a particularly strong effect 503 favoring a large EQ because it simultaneously favors increased brain and reduced body 504 mass (Fig. 4C,F). In contrast to its effect on EQ, increasing memory cost disfavors a 505 high adult skill number (Fig. 4F). That is, a higher EQ attained by increasing memory 506 costs is accompained by a decrease in skill number (Fig. 4C,F). The factors that favor a 507 large brain, large EQ, and high skill are similar with either power or exponential 508 competence (Fig. 4 and Figs. S16, S17). Importantly, although with the estimated 509 parameter values the me-against-nature setting can recover human growth patterns 510 yielding adult body and brain mass of ancient humans, our exploration of the 511 parameters that were not estimated from data suggests that the me-against-nature 512 setting cannot recover human growth patterns yielding adult body and brain mass of 513 modern ...
Context 10
... favoring a large EQ and high skill 501 A large EQ and high adult skill number are generally favored by the same factors that 502 favor a large adult brain. However, the memory cost has a particularly strong effect 503 favoring a large EQ because it simultaneously favors increased brain and reduced body 504 mass (Fig. 4C,F). In contrast to its effect on EQ, increasing memory cost disfavors a 505 high adult skill number (Fig. 4F). That is, a higher EQ attained by increasing memory 506 costs is accompained by a decrease in skill number (Fig. 4C,F). The factors that favor a 507 large brain, large EQ, and high skill are similar with either power or exponential 508 competence (Fig. 4 and Figs. S16, S17). Importantly, although with the estimated 509 parameter values the me-against-nature setting can recover human growth patterns 510 yielding adult body and brain mass of ancient humans, our exploration of the 511 parameters that were not estimated from data suggests that the me-against-nature 512 setting cannot recover human growth patterns yielding adult body and brain mass of 513 modern ...
Citations
... Our findings support the theory that postreproductive life in some mammals coevolved with multigenerational cooperation in a complex foraging niche and help explain selection against lateacting deleterious alleles. production returns and generate surpluses (2,(14)(15)(16). Because intergenerational transfers of adult surpluses can increase the fertility and survival of others (especially the young), these indirect fitness contributions could drive selection for survival well beyond ages of reproductive cessation (4,17). ...
In classical evolutionary models, the force of natural selection diminishes with age toward zero by last reproduction. However, intergenerational resource transfers and other late-life contributions in social species may select for postreproductive longevity. We present a formal framework for estimating indirect fitness contributions via production transfers in a skills-intensive foraging niche, reflecting kinship and cooperation among group members. Among contemporary human hunter-gatherers and horticulturalists, indirect fitness contributions from transfers exceed direct reproductive contributions from before menopause until ages when surpluses end, around the modal age of adult death (∼70 y). Under reasonable assumptions, these benefits are the equivalent to having up to several more offspring after age 50. Despite early independence, minimal production surplus, and a shorter lifespan, chimpanzees could theoretically make indirect contributions if they adopted reliable food-sharing practices. Our results for chimpanzees hypothetically adopting hunter-gatherer subsistence suggest that a skills-intensive foraging ecology with late independence and late peak production could select for human-like life histories via positive feedback between longevity and late-life transfers. In contrast, life history changes preceding subsistence shifts would not favor further life extension or subsistence shifts. Our results formalize the theory that longevity can be favored under socioecological conditions characterized by parental and alloparental care funded through transfers of mid- to late-life production surpluses. We also extend our analysis beyond food transfers to illustrate the potential for indirect fitness contributions from pedagogy, or information transfers. While we focus mostly on humans, our approach is adaptable to any context or species where transfers can affect fitness.
... Energy restrictions and micronutrient deficiencies during infancy and childhood are associated with impaired cognitive functions (Bellisle, 2004;Nyaradi, Li, Hickling, Foster, & Oddy, 2013;Prado & Dewey, 2014). However, the quantification of energy demands of cognition during infancy and childhood remains a topic on which we lack information (Gonzalez-Forero, Faulwasser, & Lehmann, 2017;Kaplan & Robson, 2002). Micronutrient deficiencies in undernourished children have been associated with impaired brain development (Prado & Dewey, 2014). ...
Life history theory integrates ecological, physiological, and molecular layers within an evolutionary framework to understand organisms’ strategies to optimize survival and reproduction. Two life history hypotheses and their implications for child growth, development, and health (illustrated in the South African context) are reviewed here. One hypothesis suggests that there is an energy trade-off between linear growth and brain growth. Undernutrition in infancy and childhood may trigger adaptive physiological mechanisms prioritizing the brain at the expense of body growth. Another hypothesis is that the period from conception to infancy is a critical window of developmental plasticity of linear growth, the duration of which may vary between and within populations. The transition from infancy to childhood may mark the end of a critical window of opportunity for improving child growth. Both hypotheses emphasize the developmental plasticity of linear growth and the potential determinants of growth variability (including the role of parent–offspring conflict in maternal resources allocation). Implications of these hypotheses in populations with high burdens of undernutrition and infections are discussed. In South Africa, HIV/AIDS during pregnancy (associated with adverse birth outcomes, short duration of breastfeeding, and social consequences) may lead to a shortened window of developmental plasticity of growth. Furthermore, undernutrition and infectious diseases in children living in South Africa, a country undergoing a rapid nutrition transition, may have adverse consequences on individuals’ cognitive abilities and risks of cardio-metabolic diseases. Studies are needed to identify physiological mechanisms underlying energy allocation between biological functions and their potential impacts on health.
Des gradients sociaux ont été documentés pour une variété de comportements individuels. Au sein des pays occidentaux par exemple, les personnes ayant un statut socio-économique plus bas ont tendance à investir moins dans leur éducation, à fumer davantage, sont plus susceptibles de souffrir d'obésité et plus enclines à prendre des risques dans des contextes économiques. Ainsi, être exposé à des conditions de vie précaire semble engendrer une série de comportements, covariant de manière systématique. Ce syndrome comportemental a été principalement interprété comme le produit de déficits cognitifs ayant traits à la prise de décision et/ou à un manque de volonté. Dans ce manuscrit, nous explorons une approche différente, qui s'ancre dans les explications adaptationnistes des comportements humains. Au lieu d'appréhender les comportements observés chez les individus en situation de précarité comme des anomalies, ceux-ci sont perçus comme des ajustements des stratégies individuelles d'histoire de vie, adaptés à la vie dans des environnements précaires. En effet, nous approfondirons l'hypothèse selon laquelle un environnement précaire sélectionne des stratégies qui accordent davantage de poids aux bénéfices immédiats plutôt qu’aux investissements de long terme, affectant dès lors toute une gamme de comportements. Dans un premier temps, nous analyserons par le biais de modèles d'équations structurelles, différents jeux de données afin de mesurer le degré de covariation de comportements ayant trait à la reproduction, à l'investissement dans la santé et au niveau de confiance, ainsi que leur association éventuelle avec le niveau de précarité éprouvé pendant l'enfance ou à l'âge adulte. Globalement, nos résultats indiquent qu'une réduction de l’investissement dans la santé co-varie avec une stratégie de reproduction plus court-termiste, ainsi qu'un plus faible niveau de confiance. De plus, ce pattern est surreprésenté chez les personnes en situation de précarité, avec des effets persistants des conditions pendant l'enfance. En parallèle de ces travaux empiriques, nous nous sommes par ailleurs intéressés aux fondements théoriques de nos hypothèses de travail. Précisément, nous avons développé un modèle formel de stratégie d'histoire de vie prédisant les changements de préférences temporelles intra- et interindividuelles. Celui-ci nous a permis de mettre en évidence l’importance de deux facteurs distincts pour déterminer le degré optimal avec lequel des individus doivent préférer les récompenses de court-terme : 1) le niveau d'incertitude sur la probabilité de collecter une récompense délayée dans le temps, et 2) le coût d'opportunité à ne pas bénéficier de la récompense pendant la période de délai. Enfin, nous concluons ce travail en discutant des perspectives particulièrement intéressantes offertes par une intégration plus poussée de l'approche développée dans cette thèse, avec d'autres sciences sociales et sciences du comportement plus traditionnelles.
[Target Article.] Objectives: Sexual selection typically centers on bodily and psychological traits. Non-bodily traits ranging from housing and vehicles through art to social media can, however, influence sexual selection even in absence of the phenotype proper. The theoretical framework of human sexual selection is updated in this article by unifying four theoretical approaches and conceptualizing non-bodily traits as extended phenotypic traits.
Methods:
Existing research is synthesized with extended phenotype theory, life history theory, and behavioral ecology. To test population-level hypotheses arising from the review, ecological and demographic data on 122 countries are analyzed with multiple linear regression modelling.
Results:
A four-factor model of intelligence, adolescent fertility, population density, and atmospheric cold demands predicts 64% of global variation in economic complexity in 1995 and 72% of the variation in 2016.
Conclusions:
The evolutionary pathways of extended phenotypes frequently undergo a categorical broadening from providing functional benefits to carrying signalling value. Extended phenotypes require investments in skills and bioenergetic resources, but they can improve survival in high latitudes, facilitate the extraction of resources from the environment, and substantially influence sexual selection outcomes. Bioenergetic investments in extended phenotypes create individual- and population-level tradeoffs with competing life history processes, exemplified here as a global tradeoff between adolescent fertility and economic complexity. The merits of the present model include a more systematic classification of sexual traits, a clearer articulation of their evolutionary-developmental hierarchy, and an analysis of ecological, genetic, and psychological mechanisms that modulate the flow of energy into extended phenotypes and cultural innovations.
