Explanations for adaptations, just‐so stories, and limitations on evidence in evolutionary biology

Smith, Richard J.

doi:10.1002/evan.21495

Cited by 25 publications

(25 citation statements)

References 114 publications

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“…Many explorative comparative anatomy analyses, including the present study, can be thought of as adaptationist (Gould & Lewontin, ), presenting functionally adaptive explanations for the observed data that are not easily falsified (Smith, ). Here, however, we submit that as the clearest differences in subchondral RBV/TV and DA patterns in the metacarpal heads are between the two species with the most disparate locomotor modes (orangutans and gorillas), and the least differences are between the two species with the most similar locomotor modes (chimpanzees and bonobos), this offers a kind of informal falsification.…”

Section: Discussionmentioning

confidence: 88%

Metacarpal trabecular bone varies with distinct hand‐positions used in hominid locomotion

et al. 2019

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Trabecular bone remodels during life in response to loading and thus should, at least in part, reflect potential variation in the magnitude, frequency and direction of joint loading across different hominid species. Here we analyse the trabecular structure across all non-pollical metacarpal distal heads (Mc2-5) in extant great apes, expanding on previous volume of interest and whole-epiphysis analyses that have largely focused on only the first or third metacarpal. Specifically, we employ both a univariate statistical mapping and a multivariate approach to test for both inter-ray and interspecific differences in relative trabecular bone volume fraction (RBV/TV) and degree of anisotropy (DA) in Mc2-5 subchondral trabecular bone. Results demonstrate that whereas DA values only separate Pongo from African apes (Pan troglodytes, Pan paniscus, Gorilla gorilla), RBV/ TV distribution varies with the predicted loading of the metacarpophalangeal (McP) joints during locomotor behaviours in each species. Gorilla exhibits a relatively dorsal distribution of RBV/TV consistent with habitual hyper-extension of the McP joints during knuckle-walking, whereas Pongo has a palmar distribution consistent with flexed McP joints used to grasp arboreal substrates. Both Pan species possess a disto-dorsal distribution of RBV/TV, compatible with multiple hand postures associated with a more varied locomotor regime. Further inter-ray comparisons reveal RBV/TV patterns consistent with varied knuckle-walking postures in Pan species in contrast to higher RBV/TV values toward the midline of the hand in Mc2 and Mc5 of Gorilla, consistent with habitual palm-back knuckle-walking. These patterns of trabecular bone distribution and structure reflect different behavioural signals that could be useful for determining the behaviours of fossil hominins. Hominid metacarpal trabecular bone, C. J. Dunmore et al. 47 Materials and methodsSubchondral trabecular bone was analysed in the metacarpus of P. paniscus (n = 10), P. troglodytes (n = 13), G. gorilla gorilla (n = 12), Pongo sp. indet. (n = 1), P. pygmaeus (n = 7) and P. abelii (n = 3). Hominid metacarpal trabecular bone, C. J. Dunmore et al. 48

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Section: Discussionmentioning

confidence: 88%

Metacarpal trabecular bone varies with distinct hand‐positions used in hominid locomotion

et al. 2019

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“…Investigations of sex differences in the human skeleton have faced many of the challenges in evolutionary biology that Smith described: “Some narrative explanations rely on theory‐driven assumptions that may not be shared by readers… Some will not use good judgement when taking into account how underdetermination inevitably limits what can be inferred from historical data… Some will make unreasonable assumptions about what the current utility of a feature can tell us about its historical role… Some will make unreasonable assumptions that simplify the contingency of the historical situation… Some will allow coherence and simplicity in narratives to substitute for evidence.” 93 …”

Section: Discussionmentioning

confidence: 99%

Expanding the evolutionary explanations for sex differences in the human skeleton

Dunsworth

2020

Evolutionary Anthropology

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While the anatomy and physiology of human reproduction differ between the sexes, the effects of hormones on skeletal growth do not. Human bone growth depends on estrogen. Greater estrogen produced by ovaries causes bones in female bodies to fuse before males' resulting in sex differences in adult height and mass. Female pelves expand more than males' due to estrogen and relaxin produced and employed by the tissues of the pelvic region and potentially also due to greater internal space occupied by female gonads and genitals. Evolutionary explanations for skeletal sex differences (aka sexual dimorphism) that focus too narrowly on big competitive men and broad birthing women must account for the adaptive biology of skeletal growth and its dependence on the developmental physiology of reproduction. In this case, dichotomizing evolution into proximate‐ultimate categories may be impeding the progress of human evolutionary science, as well as enabling the popular misunderstanding and abuse of it.

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“…The size of circles corresponds to the strength of the correlation identify such adaptive roots with much certainty. 85 The prevailing hypothesis on the evolutionary benefits of loneliness is based on humans having adapted to live in groups; for social creatures, loneliness may have increased the chances for survival and reproduction through the motivation to improve one's social circumstances. 1 A related evolutionary mechanism that has been widely proposed for depression is the social risk hypothesis, in which depression causes one to minimize the risk of social exclusion due to an imbalance of one's social value and social burden.…”

Section: Discussionmentioning

confidence: 99%

Predicting loneliness with polygenic scores of social, psychological and psychiatric traits

Abdellaoui

Nivard

Hottenga

et al. 2018

Genes Brain and Behavior

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Loneliness is a heritable trait that accompanies multiple disorders. The association between loneliness and mental health indices may partly be due to inherited biological factors. We constructed polygenic scores for 27 traits related to behavior, cognition and mental health and tested their prediction for self-reported loneliness in a population-based sample of 8798 Dutch individuals. Polygenic scores for major depressive disorder (MDD), schizophrenia and bipolar disorder were significantly associated with loneliness. Of the Big Five personality dimensions, polygenic scores for neuroticism and conscientiousness also significantly predicted loneliness, as did the polygenic scores for subjective well-being, tiredness and self-rated health. When including all polygenic scores simultaneously into one model, only 2 major depression polygenic scores remained as significant predictors of loneliness. When controlling only for these 2 MDD polygenic scores, only neuroticism and schizophrenia remain significant. The total variation explained by all polygenic scores collectively was 1.7%. The association between the propensity to feel lonely and the susceptibility to psychiatric disorders thus pointed to a shared genetic etiology. The predictive power of polygenic scores will increase as the power of the genome-wide association studies on which they are based increases and may lead to clinically useful polygenic scores that can inform on the genetic predisposition to loneliness and mental health.

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Explanations for adaptations, just‐so stories, and limitations on evidence in evolutionary biology

Cited by 25 publications

References 114 publications

Metacarpal trabecular bone varies with distinct hand‐positions used in hominid locomotion

Metacarpal trabecular bone varies with distinct hand‐positions used in hominid locomotion

Expanding the evolutionary explanations for sex differences in the human skeleton

Predicting loneliness with polygenic scores of social, psychological and psychiatric traits

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