Distance from Africa, not climate, explains within-population phenotypic diversity in humans

Betti, Lia; Balloux, François; Amos, William; Hanihara, Tsunehiko; Manica, Andrea

doi:10.1098/rspb.2008.1563

Cited by 141 publications

(243 citation statements)

References 27 publications

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“…All morphological regions, except for the temporal lines, were significantly correlated with climate, although these correlations disappeared once neutral genetic distance was controlled for. This supports previous studies (e.g., 16,19) suggesting that climatically driven diversifying selection has played a relatively minor role in generating global patterns of cranial variation. However, aspects of facial variation associated with thermoregulation were deliberately not tested here.…”

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confidence: 80%

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Global human mandibular variation reflects differences in agricultural and hunter-gatherer subsistence strategies

Cramon‐Taubadel

2011

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

164

153

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Variation in the masticatory behavior of hunter-gatherer and agricultural populations is hypothesized to be one of the major forces affecting the form of the human mandible. However, this has yet to be analyzed at a global level. Here, the relationship between global mandibular shape variation and subsistence economy is tested, while controlling for the potentially confounding effects of shared population history, geography, and climate. The results demonstrate that the mandible, in contrast to the cranium, significantly reflects subsistence strategy rather than neutral genetic patterns, with hunter-gatherers having consistently longer and narrower mandibles than agriculturalists. These results support notions that a decrease in masticatory stress among agriculturalists causes the mandible to grow and develop differently. This developmental argument also explains why there is often a mismatch between the size of the lower face and the dentition, which, in turn, leads to increased prevalence of dental crowding and malocclusions in modern postindustrial populations. Therefore, these results have important implications for our understanding of human masticatory adaptation.O ne of the major differences categorizing human populations is variation in subsistence strategies and related paramasticatory behavior. A shift from a primarily hunting and gathering strategy to one based on extensive horticulture or animal husbandry is known to have occurred independently on several occasions in human prehistory, yielding a correlated shift in settlement pattern, demography, population expansion, and social reorganization (e.g., 1, 2). Given the wider cultural changes associated with increased food processing and, therefore, consumption of a more homogeneous and softer diet in agriculturalists, it has been hypothesized that the dietary changes associated with agriculture are likely to have had an important effect on the form of the cranium and mandible (e.g., 3-5). Although localized studies comparing hunter-gather and farming populations in Nubia (6), South America (7), the Ohio Valley (8), and the southern Levant (9) have found some support for an associated change between the masticatory apparatus and the initial transition to agriculture, it is currently unclear what effect agriculture has had on global patterns of human mandibular variation when compared against other wider microevolutionary factors, such as gene flow, migration, and natural selection. Hence, this study represents a global comparative analysis of the effects of subsistence strategy on modern human mandibular variation.In recent decades, it has become clear that the majority of modern human cranial shape variation is congruent with a null model of neutral evolution, with relatively few morphological regions being subject to diversifying selection (e.g., 10-19). However, there appear to be two major exceptions to this general pattern. Aspects of facial morphology, and particularly nasal morphology, are likely to have been subject to diversifying natural sele...

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confidence: 80%

“…In recent decades, it has become clear that the majority of modern human cranial shape variation is congruent with a null model of neutral evolution, with relatively few morphological regions being subject to diversifying selection (e.g., [10][11][12][13][14][15][16][17][18][19]. However, there appear to be two major exceptions to this general pattern.…”

mentioning

confidence: 82%

Global human mandibular variation reflects differences in agricultural and hunter-gatherer subsistence strategies

Cramon‐Taubadel

2011

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

164

153

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“…[Interestingly, the most divergent and genetically diverse clade was from South Africa, although Linz et al (58) eliminated this as an outlier in some analyses]. Even morphological variation of human crania supports a serial founder effect model OOA (59)(60)(61). In summary, multiple independent lines of genetic evidence thus support a serial founder effect mode of dispersal.…”

Section: Independent Evidence Of Out Of Africa Modelmentioning

confidence: 75%

The great human expansion

Henn

Cavalli-Sforza

Feldman

2012

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

366

238

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Genetic and paleoanthropological evidence is in accord that today's human population is the result of a great demic (demographic and geographic) expansion that began approximately 45,000 to 60,000 y ago in Africa and rapidly resulted in human occupation of almost all of the Earth's habitable regions. Genomic data from contemporary humans suggest that this expansion was accompanied by a continuous loss of genetic diversity, a result of what is called the "serial founder effect." In addition to genomic data, the serial founder effect model is now supported by the genetics of human parasites, morphology, and linguistics. This particular population history gave rise to the two defining features of genetic variation in humans: genomes from the substructured populations of Africa retain an exceptional number of unique variants, and there is a dramatic reduction in genetic diversity within populations living outside of Africa. These two patterns are relevant for medical genetic studies mapping genotypes to phenotypes and for inferring the power of natural selection in human history. It should be appreciated that the initial expansion and subsequent serial founder effect were determined by demographic and sociocultural factors associated with hunter-gatherer populations. How do we reconcile this major demic expansion with the population stability that followed for thousands years until the inventions of agriculture? We review advances in understanding the genetic diversity within Africa and the great human expansion out of Africa and offer hypotheses that can help to establish a more synthetic view of modern human evolution.human population growth | hunter-gatherer demography | molecular evolution

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“…In order to test the findings of previous studies showing that different cranial regions preserve population history and climatic signatures differentially (Harvati and Weaver, 2006a,b;Smith, 2009), three morphological distance matrices were calculated: one for the whole skull, one considering only facial variables, and the last one considering only neurocranial variables (Table 1). As genetic data are not available for all the populations included in this study, we used geographic distances as a proxy for genetic relationships, assuming a pattern of diversification through isolation by distance in accordance with the findings of Relethford and others (e.g., Relethford, 2004a;Manica et al, 2007;Betti et al, 2009). Geographic distance consisted of the linear distance between groups in kilometers, using Cairo, Bangkok, Bering and Panamá as check-points to limit the distances to terrestrial routes; and climate matrices are simply the differences among series for each climate variable.…”

Section: Methodsmentioning

confidence: 99%

“…Craniometric data have been found to follow a common geographic pattern with genetic markers, including both classical and microsatellite DNA markers (Relethford, 1994(Relethford, , 2004a(Relethford, , 2009Manica et al, 2007;Betti et al, 2009). These findings have been interpreted as resulting from an isolation-by-distance model of evolutionary diversification.…”

mentioning

confidence: 99%

Climate Signatures in the Morphological Differentiation of Worldwide Modern Human Populations

Hübbe

Hanihara

Harvati

2009

The Anatomical Record

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The ability of cranial morphology to reflect population/phylogenetic history, and the degree to which it might be influenced by environmental factors and selection pressures have been widely discussed. Recent consensus views cranial morphology as largely indicative of population history in humans, with some anatomical cranial regions/measurements being more informative on population history, while others being under selection pressure. We test earlier findings using the largest and most diverse cranial dataset available as yet: 7,423 male specimens from 135 geographic human population samples represented by 33 standard craniometric linear measurements. We calculated Mahalanobis D 2 for three datasets: complete cranial dataset; facial measurement dataset; and neurocranial measurement dataset; these morphological distance matrices were then compared to matrices of geographic distances as well as of several climatic variables. Additionally, we calculated Fst values for our cranial measurements and compared the results to the expected Fst values for neutral genetic loci. Our findings support the hypothesis that cranial, and especially neurocranial morphology, is phylogenetically informative, and that aspects of the face and cranium are subject to selection related to climatic factors. The Fst analysis suggest that selection to climate is largely restricted to groups living in extremely cold environments, including Northeast Asia, North America, and Northern Europe, though each of these regions appears to have arrived at their morphology through distinct adaptive pathways. Anat Rec, 292:1720Rec, 292: -1733Rec, 292: , 2009. Key words: Fst; craniometrics; adaptation; population history; human variation; NeanderthalsThe degree to which human cranial morphology reflects population history or adaptive and developmental changes related to environmental conditions is the subject of ongoing scientific discussion in anthropology. Our understanding of the evolutionary processes affecting morphological variation directly impacts both the study of modern human geographic diversity as well as the interpretation of the human fossil record. The relevance of cranial morphology to phylogenetic reconstruction has been questioned in the past (see e.g., Collard and Wood, 2000), and convergence, parallelism, reversals, and environmen-

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Distance from Africa, not climate, explains within-population phenotypic diversity in humans

Cited by 141 publications

References 27 publications

Global human mandibular variation reflects differences in agricultural and hunter-gatherer subsistence strategies

Global human mandibular variation reflects differences in agricultural and hunter-gatherer subsistence strategies

The great human expansion

Climate Signatures in the Morphological Differentiation of Worldwide Modern Human Populations

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