Rasgos Esqueletales De Adaptación Al Clima Y a La Actividad Entre Los Habitantes Aborígenes De Tierra Del Fuego

Pearson, Osbjorn M.; Millones, Y Mario

doi:10.4067/s0718-22442005000100003

Cited by 11 publications

(20 citation statements)

References 15 publications

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“…This pattern also could be the result of a balance of factors such as gene flow and directional selection (Slatkin 1987; Barton et al 2007). Natural selection could favor the adaptations to local conditions, leading to the divergence of southernmost populations (i.e., Tierra del Fuego groups) during the Holocene (Pearson and Millones 2005). Gene flow among Tierra del Fuego and other South American groups may spread new genes among populations (Slatkin 1987), generating the clinal pattern of variation among populations observed during the later late Holocene.…”

Section: Discussionmentioning

confidence: 99%

Nonrandom Factors in Modern Human Morphological Diversification: A Study of Craniofacial Variation in Southern South American Populations

Pérez

Monteiro

2009

Evolution

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The causes of craniofacial variation among human populations have been the subject of controversy. In this work, we studied aboriginal populations from southern South America, the last continental region peopled by humans and with a wide range of ecological conditions. Because of these characteristics, southern South America provides a unique opportunity to study the relative importance of random and nonrandom factors in human diversification. Previous craniometric studies recognized remarkable differences among populations from this region, usually resorting to random factors as the main explanation. In contrast, here we suggest, using tests based on quantitative genetic models, that: (1) the rate of craniofacial divergence among these populations is too high and (2) the patterns of variation within and between populations are too different to be explained by genetic drift alone. In addition, the among-sample craniofacial variation is correlated with climate and diet but not with mtDNA variation. We suggest that the influence of nonrandom factors (e.g., plasticity, selection) on human craniofacial diversification in regions with large ecological variation is more important than generally acknowledged and capable to generate large craniofacial divergence in a short period of time. These results bring nonrandom factors into focus for the interpretation of human craniofacial variation. K E Y W O R D S :Ecological variation, evolutionary rates, geometric morphometrics, Patagonian populations.

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Section: Discussionmentioning

confidence: 99%

Nonrandom Factors in Modern Human Morphological Diversification: A Study of Craniofacial Variation in Southern South American Populations

Pérez

Monteiro

2009

Evolution

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“…Therefore, nonrandom factors could be important in shaping the patterns of variation in robust traits in this region. Within these factors, the hypotheses most frequently cited are biomechanical and climatic, but there are other potential factors such as nutrition (Hernandez et al, 1997;Lalueza et al, 1997;Pearson and Millones, 2005;Bernal et al, 2006). These factors are a probable cause of divergence in the region under study.…”

Section: Discussionmentioning

confidence: 99%

“…In addition, they inhabited diverse environments with mean annual temperatures from 23 in northernmost to 4 in southernmost populations. Since populations displaying most robust traits inhabited the coldest areas of South America, it was suggested that cranial and postcranial robusticity could be related to an adaptation to low temperatures (Pearson and Millones, 2005;Bernal et al, 2006). Further research is required to reveal how these factors could led to differences among populations in the size and the pattern of shape change during ontogeny.…”

Section: Discussionmentioning

confidence: 99%

Ontogeny of robusticity of craniofacial traits in modern humans: A study of South American populations

González

Pérez

Bernal

2009

American J Phys Anthropol

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To date, differences in craniofacial robusticity among modern and fossil humans have been primarily addressed by analyzing adult individuals; thus, the developmental basis of such differentiation remains poorly understood. This article aims to analyze the ontogenetic development of craniofacial robusticity in human populations from South America. Geometric morphometric methods were used to describe cranial traits in lateral view by using landmarks and semilandmarks. We compare the patterns of variation among populations obtained with subadults and adults to determine whether population-specific differences are evident at early postnatal ontogeny, compare ontogenetic allometric trajectories to ascertain whether changes in the ontogeny of shape contribute to the differentiation of adult morphologies, and estimate the amount of size change that occurs during growth along each population-specific trajectory. The results obtained indicate that the pattern of interpopulation variation in shape and size is already established at the age of 5 years, meaning that processes acting early during ontogeny contribute to the adult variation. The ontogenetic allometric trajectories are not parallel among all samples, suggesting the divergence in the size-related shape changes. Finally, the extension of ontogenetic trajectories also seems to contribute to shape variation observed among adults. Fossil species of the genus Homo are characterized by high levels of craniofacial robusticity, which is defined by a diverse array of morphological traits. Robusticity is attributed to crania that possess large superstructures such as brow ridges, mastoid processes, occipital torus, and nuchal crest (Lahr and Wright, 1996), large external dimensions, thick vault bones (Lieberman, 1996), or rugged muscle markings. There is a marked trend toward a reduction in robusticity in several regions of the world, and most modern humans have gracile crania. However, some hunter-gatherer populations from continental Patagonia and Tierra del Fuego (southern South America) as recent as late Holocene (ca. 3,000 years 14 C B.P. to historical times), as well as Australian aborigines, display numerous robust traits that depart from the majority of modern populations (Lahr, 1995;Lahr and Wright, 1996;Lalueza et al., 1997;Sardi, 2002;Bernal et al., 2006;Curnoe and Thorne, 2006). Their crania have been identified as the most robust of any modern population due to the pronounced development of supraorbital ridges, glabellar regions and supercilliary arches (Lahr and Wright, 1996;Bernal et al., 2006).The patterns of craniofacial robusticity in modern and fossil humans have been mainly assessed by analyzing adult individuals, and thus the developmental basis of such differentiation remains untested. Because morphological variation within and between populations appears during ontogeny, the study of ontogenetic series could provide important clues regarding the kinds of changes responsible for size and shape patterns observed among adult crania. The role of ...

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“…On the other hand, numerous features that result from adaptation to a cold climate characterize populations living at low temperatures. For instance, the shape of the nasal aperture (González-José, 2003;Hernández et al, 1997), the body proportions, and the postcranial robusticity (Pearson and Millones, 2005) of Fueguians were hypothesized to be climatic responses. Considering the relevance of climatic factors to explain morphological variation, the climatic hypothesis is proposed here as a causal factor of craniofacial robusticity in Fueguian-Patagonian populations.…”

mentioning

confidence: 99%

Variation and causal factors of craniofacial robusticity in Patagonian hunter-gatherers from the late Holocene

2006

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Fueguian-Patagonian skulls have been characterized as some of the most robust of any modern crania. However, the causal factors of such robusticity remain unsettled. We assess within- and among-sample cranial robusticity of seven samples from continental Patagonia and Tierra del Fuego, using geometric morphometric techniques. In addition, the biomechanical, phylogenetic, and climatic hypotheses proposed to account for robusticity in such samples are discussed. Two Amerindian samples of farmers and two early middle Holocene samples from South America were included. The results show: 1) large variation in craniofacial robusticity among Patagonian samples, with the highest robusticity in samples from south continental Patagonia and Isla Grande of Tierra del Fuego, whereas central and north Patagonian samples display the same degree of robusticity as farmer samples; 2) that early middle Holocene samples display lower levels of robusticity than South Patagonian samples; and 3) strong association between latitude and craniofacial robusticity, with the most robust craniofacial morphologies occurring at the highest latitudes. In consequence, neither masticatory stress nor retention of ancestral features is supported by the morphological evidence analyzed. Hence it is hypothesized that endocrine changes related to cold climate may be a plausible explanation for several craniofacial features found in Fueguian and south continental Patagonian samples, such as their large masticatory component, and pronounced supraorbital ridge and glabellar region.

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Rasgos Esqueletales De Adaptación Al Clima Y a La Actividad Entre Los Habitantes Aborígenes De Tierra Del Fuego

Cited by 11 publications

References 15 publications

Nonrandom Factors in Modern Human Morphological Diversification: A Study of Craniofacial Variation in Southern South American Populations

Nonrandom Factors in Modern Human Morphological Diversification: A Study of Craniofacial Variation in Southern South American Populations

Ontogeny of robusticity of craniofacial traits in modern humans: A study of South American populations

Variation and causal factors of craniofacial robusticity in Patagonian hunter-gatherers from the late Holocene

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