Pervasive Genetic Integration Directs the Evolution of Human Skull Shape

Martínez‐Abadías, Neus; Esparza, Mireia; Sjøvold, Torstein; González‐José, Rolando; Santos, Mauro; Hernández, Miguel; Klingenberg, Christian Peter

doi:10.1111/j.1558-5646.2011.01496.x

Cited by 103 publications

(110 citation statements)

References 97 publications

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“…Although frontal changes also can influence this variable, researchers have suggested that globularization is driven by upper parietal reorganization and that this anatomical change can be associated with enhanced visuospatial integration and memory in modern humans (17). The comparatively fast evolution of the dorsal arc trait in the lineage leading to H. sapiens is consistent with such a link between brain anatomy and function, although it could be an indirect result of selection on other craniofacial hard-tissue changes (18). If some individuals that do not show a globular anatomy, such as Jebel Irhoud 1 and 2 and Omo 2, are early members of H. sapiens (19), then the endocranial anatomy typical of modern humans may have evolved within the H. sapiens lineage.…”

Section: Significancementioning

confidence: 94%

Brain enlargement and dental reduction were not linked in hominin evolution

Gómez‐Robles

Smaers

Holloway

et al. 2017

Proc. Natl. Acad. Sci. U.S.A.

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The large brain and small postcanine teeth of modern humans are among our most distinctive features, and trends in their evolution are well studied within the hominin clade. Classic accounts hypothesize that larger brains and smaller teeth coevolved because behavioral changes associated with increased brain size allowed a subsequent dental reduction. However, recent studies have found mismatches between trends in brain enlargement and posterior tooth size reduction in some hominin species. We use a multiple-variance Brownian motion approach in association with evolutionary simulations to measure the tempo and mode of the evolution of endocranial and dental size and shape within the hominin clade. We show that hominin postcanine teeth have evolved at a relatively consistent neutral rate, whereas brain size evolved at comparatively more heterogeneous rates that cannot be explained by a neutral model, with rapid pulses in the branches leading to later Homo species. Brain reorganization shows evidence of elevated rates only much later in hominin evolution, suggesting that fast-evolving traits such as the acquisition of a globular shape may be the result of direct or indirect selection for functional or structural traits typical of modern humans.endocast | postcanine teeth | evolutionary rates | selection | paleoanthropology I n comparison with other hominins, modern humans are characterized by their large brain and small posterior teeth. These traits are among our most distinctive features, and trends in their evolution are well studied because of the phylogenetic and functional implications of variation in dental and cerebral anatomy (1-3). Brain expansion and postcanine reduction appear to follow parallel trends during hominin evolution, and classic views consider that an increase in brain size was linked to more complex behavior that included the manufacture and use of stone tools, which allowed a subsequent dental reduction. A shift toward a higher-quality diet during the evolution of early Homo also has been related to brain size increase and posterior tooth reduction (4, 5). However, it has been suggested recently that brain expansion in early Homo, as inferred from endocranial volume, substantially preceded dental reduction (6). It also has been noted that early in the Neanderthal lineage strong dental reduction preceded the additional brain expansion seen in the later "classic" Neanderthals (7). The suggestion that stone tool use and manufacture substantially predated the increase in brain size observed in early Homo (8) adds further complexity to this scenario.Recent developments in ancestral state reconstruction (9, 10) allow lineage-specific patterns of brain expansion and dental reduction to be quantified and compared. Unlike traditional approaches to ancestral state reconstruction that assume a neutral evolutionary scenario, which is likely unrealistic in most cases, we used a variable rate approach that estimates differences in evolutionary rates across different branches of a given phylogeny. We appli...

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Section: Significancementioning

confidence: 94%

Brain enlargement and dental reduction were not linked in hominin evolution

Gómez‐Robles

Smaers

Holloway

et al. 2017

Proc. Natl. Acad. Sci. U.S.A.

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“…Genetic integration between parts means that selection on one part will produce a correlated response in other parts, whereas genetic modularity can facilitate independent evolutionary changes in different parts [3,7,8]. Studies combining geometric morphometrics and quantitative genetics have investigated correlated responses by simulating selection for a highly localized shape change and observing whether the evolutionary response affects other parts as well [67,[71][72][73].…”

Section: (D) Genetic Integrationmentioning

confidence: 99%

“…A large number of studies has compared static integration among individuals to fluctuating asymmetry and obtained widely variable results, indicating that the relationship between static and developmental integration differs according to taxa and other circumstances [10-15,36,37,48 -53,110]. Genetic integration has mostly been compared to static phenotypic integration, reflecting the importance of the genetic and phenotypic covariance matrices in quantitative genetic theory [67,71,73]. Evolutionary integration has been compared to static within-taxon integration [16,25,95] and ontogenetic variation [35,85,87,88], and through links to ecological variables such as diet or direct biomechanical arguments, functional considerations have also been incorporated [63,113].…”

Section: Examples Of Comparisons Across Levelsmentioning

confidence: 99%

Studying morphological integration and modularity at multiple levels: concepts and analysis

Klingenberg

2014

Phil. Trans. R. Soc. B

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278

301

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Although most studies on integration and modularity have focused on variation among individuals within populations or species, this is not the only level of variation for which integration and modularity exist. Multiple levels of biological variation originate from distinct sources: genetic variation, phenotypic plasticity resulting from environmental heterogeneity, fluctuating asymmetry from random developmental variation and, at the interpopulation or interspecific levels, evolutionary change. The processes that produce variation at all these levels can impart integration or modularity on the covariance structure among morphological traits. In turn, studies of the patterns of integration and modularity can inform about the underlying processes. In particular, the methods of geometric morphometrics offer many advantages for such studies because they can characterize the patterns of morphological variation in great detail and maintain the anatomical context of the structures under study. This paper reviews biological concepts and analytical methods for characterizing patterns of variation and for comparing across levels. Because research comparing patterns across level has only just begun, there are relatively few results, generalizations are difficult and many biological and statistical questions remain unanswered. Nevertheless, it is clear that research using this approach can take advantage of an abundance of new possibilities that are so far largely unexplored.

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“…Morphological integration in human skull has evoked curiosity of the neuropsychiatry investigators for long. It has now been established through various scientific methods (3)(4)(5)(6) and its molecular and genetic basis (3,7) has also been established.…”

Section: Introductionmentioning

confidence: 99%

“…An ontogenetic evolutionarily linking integration, of phenotypic variations across generations in hominid skulls, has also been marked in literature (13,15). The narratives derived from available studies suggest that accumulating effects of erroneous craniocerebral development, which have been registered in the genomic structure of a population following the evolutionary trail, may emerge as a neuropsychiatric disorder (3,(16)(17)(18).…”

Section: Introductionmentioning

confidence: 99%

Morphological integration in human skull and its possible role in etiogenesis of neuropsychiatric disorders: Deciphering the link between evolution, development and disease

A.¹

2017

Preprint

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Structure-function interdependence is a universal phenomenon in biological systems. Any alteration in structural features may result in change in functions-leading to natural selection of a particular trait, or dysfunctions thereof. Many such alterations arise during the course of evolution of a species and may meticulously be traced during embryonic development of an organism. Through, the theoretical construct of morphological integration, a set of phenotypic traits alter in a coordinated and integrated manner during evolution and embryonic development of an organism yielding efficient and environmentally adapted physiological functions pertinent to those structures. Such integration may go awry sometimes, setting the basis for genesis of diseases.Morphological integration in human skull has been established through various methods. The brain-skull co-development is handcuffed through evolution and development, and the very basis of a neuropsychiatric disorder could be underlying in dysmorphogenesis of the skull, its consequent effect on structures, and thus functions of the pertinent brain components. Here we propose that morphological integration in human skull may be mechanistically implied in etiogenesis of certain neuropsychiatric disorders and should be borne in mind during clinical diagnosis and therapeutic interventions.

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Pervasive Genetic Integration Directs the Evolution of Human Skull Shape

Abstract: Evolution of morphological structures results from the response to various selection pressures, constraints, gene flow, and random drift, but their relative importance is the subject of continuing debate (Maynard Smith et

Cited by 103 publications

References 97 publications

Brain enlargement and dental reduction were not linked in hominin evolution

Brain enlargement and dental reduction were not linked in hominin evolution

Studying morphological integration and modularity at multiple levels: concepts and analysis

Morphological integration in human skull and its possible role in etiogenesis of neuropsychiatric disorders: Deciphering the link between evolution, development and disease

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