Modern human origins: continuity, replacement, and masticatory robusticity in Australasia

Morphological evidence for a Multiregional (MR) model of human origins is suggested by a series of “linking traits” seen in the crania of late Javanese Homo erectus from Ngandong and anatomically modern Australian crania. A few studies that consider the genetic, structural, or functional aspects of these regional traits suggest their appearance is heavily influenced not by shared phylogeny but by a common “strong” masticatory pattern. Using dental occlusal areas, external mandibular metrics, internal biomechanical properties of the mandibular corpus measured from CT scans, and nonmetric traits associated with the attachment of masticatory muscles, we test the hypothesis that Australians exhibit evidence of a “strong” masticatory pattern. We use a mixed-sex comparative human sample (n = 415) that includes precontact Alaskans from Point Hope and the Aleutian Islands, Californians, Peruvians, an urban forensic sample, and the late Pleistocene Afalou-Taforalt sample. In comparison with recent humans known to exhibit such patterns, Australian mandibles show none of the expected changes related to producing and dissipating heavy occlusal loads. This is true regardless of whether external or internal mandibular dimensions are considered, albeit Australians show large occlusal areas and relatively large section modulus indices. Thus, a prime functional argument proposed for the origin of some Australian regional features is not supported by these data.     

Additional fossil Theropithecus from Hopefield, South Africa: a comparison with other African sites and a reevaluation of its taxonomic status

Additional fossil Theropithecus remains, recovered from mid to late Pleistocene deposits near Hopefield , South Africa, include portions of the jaws of at least five individuals. Extensive comparisons with fossil Theropithecus from other African sites, including Makapan , Swartkrans , Kanjera , Olorgesailie , and Olduvai , reveal few morphological differences, especially when variation in modern gelada baboons ( Theropithecus gelada ) and savannah baboons (Papio) is considered. The most pronounced differences between fossil forms are overall size and relative P3 length. However, these traits do not separate the fossil forms either chronologically or geographically. Other traits, such as depth of the fossa of the mandibular corpus, slope of the upper symphyseal shelf, and variation in the depth of the mandibular corpus, do not distinguish alleged primitive forms ( Makapan and lower beds at Olduvai ) from remains found at Hopefield , Swartkrans , Kanjera , Olorgesailie , Olduvai Bed IV, or the lower Ndutu Beds. Other traits, such as canine crown height and incisor size, are poorly documented for fossil Theropithecus . Thus, the available evidence suggests that Theropithecus darti and its successional species, T. oswaldi , can best be considered as a single fossil species, T. oswaldi , of which the remains from Hopefield are a late representative. Furthermore, lack of morphological differences dictates that Hopefield Theropithecus not be considered a distinct subspecies. Variation within the Hopefield sample shows that only one taxa is found at this site. Hypothesized physical and climatic conditions at Hopefield during the Pleistocene suggest that T. oswaldi lived near vleis or fresh water lagoons. Comparisons with modern T. gelada suggest a graminivorous diet for the fossil form.     

Modern human origins in Australasia: testing the predictions of competing models.

The evolutionary background to the emergence of modern humans remains controversial. Four models have been proposed to explain this process and each has clearly definable and testable predictions about the geographical origins of early Australians and their possible biological interaction with other Pleistocene populations. The present study considers the phenetic affinities of early Australians from Kow Swamp (KS 1 and KS 5) and Keilor to Pleistocene Africans and Asians from calvarial dimensions. The study includes analyses employing log-transformed and size-corrected (Mosimann variables) data. The strongest signals to emerge are as follows: (1) a phenetic pattern in which Australians are most like each other, (2) all three crania possess a mosaic of archaic and modern features, (3) Kow Swamp crania also show strong affinities to archaic remains, (4) Keilor is more modern than KS 1 and KS 5 and (5) Keilor shows affinities to Pleistocene East Asian modern crania (Liujiang and Upper Cave 101) providing evidence for a broad regional morphology. The results refute the predictions of multi-species replacement models for early Australians but are consistent with single-species models. Combined with published evidence from DNA, the present study indicates that the Assimilation model presently offers the best explanation for the origins of Pleistocene Australians.     

Frontal and facial flatness of major human populations

In the present study, the frontal and facial features of 112 populations from around the world are compared in terms of frontal and facial flatness measurements. Univariate analyses and canonical correlation analysis were applied to six indices representing flatness of frontal and facial bones. The deep infraglabellar notch, marked prognathism, and flat frontal bone show distinctive Australian/Melanesian characters among recent populations. Very flat faces in the transverse plane are the most common condition in eastern Asians. Some subSaharan Africans share similar characteristics with Australians in terms of marked prognathism and flat frontal bones in the sagittal plane on the one hand, and with eastern Asians on the other hand, for flat nasal and zygomaxillary regions. These results are not necessarily inconsistent with the evidence for regional continuity. The examination of relationships between frontal and facial flatness through canonical correlation analysis reveals a significant association between morphological features such as a deep infraglabellar notch, prognathism, flat frontal bone, and flat faces in the transverse plane. In this context, together with the generalized features of the late Pleistocene fossil record, the features of Australians having transversely projecting faces and of eastern Asians showing weak infraglabellar notches, ortho-/mosognathism, and rounded frontal bones can be interpreted as a differential retention of ancestral traits of anatomically modern humans. This may allow us to suppose that the frontal and facial flatness features treated herein can be explained by the hypothesis of a single origin of anatomically modern humans.     

现代各主要人群额骨3D几何形态的对比

额骨是连接面颅和脑颅的重要头骨组成部分,关于现代各个人种的额骨形态是否存在明显的差别,这些人种额骨的基本形态如何,变异范围以及与其他人群的相似与差异等问题都尚未完全厘清。而额骨的很多特征由于技术手段的限制很难进行测量和准确的描述比较。鉴于这些问题,本文将采用基于三维表面半标志点的几何形态测量方法,研究东亚现代人额骨的表面形态及其变异范围,并与欧洲,东南亚,美洲,非洲以及澳洲的现代人群的额骨形态进行对比,为对比不同人群的形态研究建立基础数据。结果显示,额骨形态的变异主要表现在:1)额骨鳞部的额结节和正中矢状脊共同向前隆起或回缩以及相对额骨宽度;2)眉弓的粗壮程度,额结节的侧向发育程度和正中矢状脊的发育情况。为了进一步揭示中国现代人与其他人群在额骨形态上的关系,本文还探讨了额骨大小在不同人群中的差异。结果显示,东亚现代人和欧洲现代人额骨中心大小值的中位数最大,澳洲现代人的最小。东亚现代人的额骨形态与澳洲,欧洲和非洲均有非常显著的差异。为了检验额骨的形态是否与遗传距离一致,作者还对额骨形态距离和遗传距离做了相关性分析。结果显示,不同人群的额骨形态与其遗传距离呈显著的相关性,说明本研究结果中不同人群额骨形态上的差异大小可以在一定程度上反映其遗传距离,并可能进一步反映人群历史。东亚现代人的额骨平均形态在与各个人群比较过程中表现出一致性特征,可能在一定程度上反映了东亚现代人群的进化过程是相对独立的。未来额骨的三维几何形态测量可通过扩大标本数量进一步探讨不同性别和不同演化阶段之间的差异。     

Mandibular condyle traits in Neanderthals and other Homo: a comparative,correlative, and ontogenetic study

The relationship between the mandibular condyle and the crest of the mandibular notch (CMN) has historically entered into discussions of Neanderthal characteristics and was recently suggested to be autapomorphic in Neanderthals. The Neanderthal CMN has been described as intersecting the condyle in the middle, while the modern human CMN runs to the condyle's lateral end. A large lateral condylar tubercle (LCT) has also been observed in Neanderthals and thought to be related to medial (or less lateral) CMN position. In addition, the presence of a less lateral CMN early in ontogeny, as seen in the Amud 7 infant, has been argued to demonstrate great evolutionary divergence in Neanderthals. Using a scoring system for each trait, this study first examines the expression of CMN position and LCT size in 102 adult modern humans and in samples of Neanderthals and other fossil Homo. Then, CMN position is scored in 208 subadult modern humans to elucidate the ontogeny of this trait. Results show that CMN position is not autapomorphic in Neanderthals, but Neanderthals have significantly more CMNs in the least-lateral score category than does the modern human sample. Large LCTs are found to be strongly predictive of less lateral CMN position, although less lateral CMN position may exist in the absence of a large LCT. The complex ontogenetic pattern of CMN expression observed indicates that features of subadult and adult condylar morphology cannot be constructively compared without first considering subadult morphology on its own functional and developmental terms.     

New characters for the functional interpretation of primate scapulae and proximal humeri

The study of muscle function in nonhuman primates through the technique of electromyography (EMG) has facilitated the identification of specific functional roles for muscles in particular behaviors. This has led to a more complete understanding of the biomechanics of certain regions of the musculoskeletal system, and should facilitate our ability to identify morphological features useful in the functional interpretation of fossil material. The current paper represents one such investigation of a new set of morphometric characters of the scapula and proximal humerus suggested by EMG analyses of shoulder muscle function. A set of new metric variables were examined on the scapulae and proximal humeri of 25 species of extant anthropoid primates, as well as on casts of scapulae and humeri of three fossil primate taxa. The variables are primarily related to the line of action and attachments of the rotator cuff muscles. The position of the scapular spine, the degree of lateral expansion of the subscapular fossa, the size and shape of the subscapularis insertion facet on the lesser tubercle, and the orientation of the infraspinatus insertion facet on the greater tubercle all appear to successfully sort the extant taxa into locomotor groups. Their appearance on the fossil specimens generally supports previous functional interpretations of each taxon's locomotor abilities based on a variety of other characters, suggesting that these traits are equally applicable to fossil material. © Wiley-Liss, Inc.     

Dental morphology and odontometry of the Tibetan immigrants

Dental features such as size, shape, cusp number and groove pattern, deflecting wrinkle, protostylid, form and size of dental arch and occlusion pattern, as well as crown diameters of maxillary and mandibular dentition of the Tibetan immigrants in India are described. Sex differences in various measurements are also noted. Overall reduction in size, presence of hypodontia of the third molar, and absence of Carabelli's trait are a distinct progressive/evolutionary trend in the Tibetan dentition, while presence of a shovel-shaped lingual surface of central and lateral incisors is a retrogressive/primitive condition. In some of the dental features Tibetans resemble Caucasoid and modern populations, in certain others they resemble other Mongoloid populations, and in still other features they resemble aboriginal populations and fossil hominids.     

Changes in articular eminence morphology with dental function

Measurements of mandibular fossa depth and slope of the articular eminence were obtained for human skeletal samples chosen to represent a wide spectrum of subsistence strategies and oral function: hunter-gatherers (Eskimos, Australians), American Indians dependent to a variable extent on maize agriculture, and early twentieth century American whites and blacks. In the Eskimo and Australian samples, a generalized and steady increase in fossa depth and slope was observed with increasing functional age (tooth wear) through wear level 5 (of 8), followed by a levelling off or slight decrease in fossa depth in later wear levels on the anterior teeth and a sharp decrease in fossa depth in later wear levels on the molars. Although much less consistent due in part to extensive and early molar loss, patterns of variation in the remaining samples were characterized overall by a decrease in fossa depth and slope with increasing wear, especially on the molars. Further, in those samples with high incidences of posterior tooth loss, fossa depth was routinely less and the eminence more gently sloped in subsamples having experienced molar loss than in subsamples retaining all their molars. These data provide evidence that the temporomandibular joint (TMJ) undergoes continuous morphological alteration throughout adult life, and that these alterations are probably mediated by dental function. Moreover, they suggest that differences in patterning of such alterations may exist among human groups with contrasting patterns of tooth use.     

Whole-Genome Genetic Diversity in a Sample of Australians with Deep Aboriginal Ancestry

Australia was probably settled soon after modern humans left Africa, but details of this ancient migration are not well understood. Debate centers on whether the Pleistocene Sahul continent (composed of New Guinea, Australia, and Tasmania) was first settled by a single wave followed by regional divergence into Aboriginal Australian and New Guinean populations (common origin) or whether different parts of the continent were initially populated independently. Australia has been the subject of relatively few DNA studies even though understanding regional variation in genomic structure and diversity will be important if disease-association mapping methods are to be successfully evaluated and applied across populations. We report on a genome-wide investigation of Australian Aboriginal SNP diversity in a sample of participants from the Riverine region. The phylogenetic relationship of these Aboriginal Australians to a range of other global populations demonstrates a deep common origin with Papuan New Guineans and Melanesians, with little evidence of substantial later migration until the very recent arrival of European colonists. The study provides valuable and robust insights into an early and important phase of human colonization of the globe. A broader survey of Australia, including diverse geographic sample populations, will be required to fully appreciate the continent''s unique population history and consequent genetic heritage, as well as the importance of both to the understanding of health issues.     

Population variation in tooth, jaw, and root size: a radiographic study of two populations in a high-attrition environment

Radiographs were taken of the jaws of skeletal remains of two populations of different-phenotype Prehistoric Australians from Roonka and Early New Zealanders (Maoris). On these radiographs crown, root, and corpus size were measured. Corpus height was subdivided into alveolar bone height, defined as the bone superior to the mandibular canal, and basal bone height, defined as that inferior to the mandibular canal. Both between and within the two populations there was a significant and negative correlation between crown size and corpus height. The differences between the two populations in corpus height were associated with differences in alveolar bone height rather than basal bone height and support hypotheses associating continued eruption of adult teeth with growth of the alveolar bone. The findings also support previous studies that have shown only a low correlation between crown size, root size, and corpus height.     

The view from down under: a test of the multiregional hypothesis of modern human origins using the basicranial evidence from Australasia

Proponents of the Multiregional Hypothesis of modern human origins have consistently stated that Australasia provides one of the most compelling examples of regional continuity in the human fossil record. According to these workers, features found in the earliest Homo erectus fossils from Sangiran, Central Java, can be traced through more advanced hominids from Ngandong and are found in fossil and recent Australian Aborigines. In order to test the hypothesis that a close evolutionary relationship exists amongst the fossils from Australasia, this study will examine the cranial base. This region of the skull is considered to be evolutionarily conservative and has relatively good representation and preservation throughout much of the Australasian record. The results of this project highlight a number of features on the cranial base in the Ngandong sample that appear to be unique not only within the region, but in the human fossil sample as a whole. Several of these features, such as the morphology of the foramen ovale, the location of the squamotympanic fissure in the roof of the temporomandibular fossa, and the extreme expression of the postcondyloid tuberosities have been pointed out by workers such as Weidenreich and Jacob in their surveys of this material. The presence of these characters in the Ngandong population, and their apparent lack of expression outside of this group, provides strong evidence of discontinuity in the Australasian fossil record.     

Skull of Catopithecus browni,an early tertiary catarrhine

Fossil crania from quarry L-41, Fayum, Egypt, representing Catopithecus browni, a primate similar in size to callitrichids but with a catarrhine dental formula, provide the geologically earliest record of an anthropoidean skull. Catopithecus had postorbital closure developed to the stage seen in extant anthropoideans, with direct contact between zygomatic plate and maxillary tuber, isolating an anterior orbital fissure from the inferior orbital fissure. The auditory region also resembles that of later anthropoideans: The posterior carotid foramen is placed adjacent to the jugular fossa; a large promontory canal crosses the promontorium; and the annular ectotympanic is fused ventrally to the bulla. The incisors and canines show an assemblage of features found only among modern anthropoideans and adapoids. The face is characterized by a relatively deep maxilla, broad ascending wing of the premaxilla, and long nasal bones, yielding a moderate muzzle similar to that of Aegyptopithecus. The small braincase bears an anteriorly broad frontal trigon and a posteriorly developed sagittal crest. The mandibular symphysis is unfused even in mature adults. The encephalization quotient (EQ) probably falls within the range of Eocene prosimians, much lower than the EQs of Neogene anthropoideans. © 1996 Wiley-Liss, Inc.     

现代各主要人群中面部3D几何形态的对比

中面部的形态是个人识别的重要依据,并且长期以来都在各人种的形态对比研究中占有重要的地位。而中面部骨骼形态复杂,骨骼表面不规则,很难用传统的方法来进行测量和比较。本文采用基于三维表面半标志点的几何形态测量学研究东亚现代人中面部的形态及其变异范围,并与其他各大地理位置中的现代人群的中面部形态进行对比,为人类演化和对比不同人群的形态研究建立基础数据。本研究结果显示中面部形态能够大致区分各个现代人群,其中东亚现代人与除美洲印第安人以外的所有现代人的中面部形状之间都具有较为明显的差异。东亚现代人与澳大利亚和非洲的现代人中面部形状之间的差别最明显,而与欧洲和东南亚现代人的分布范围有部分重叠。东亚现代人群中面部的平均形状却具有非常明显的特点:沿着正中矢状面的结构回缩,而两侧的结构向前方和两侧突出。而其他现代人群的中面部平均形状则呈现出相反的特征,即沿着正中矢状面的结构为突出,而两侧的结构回缩的特征。这些特点在东亚发现的化石人类标本中也有很高的发生率,这表明这些中面部特征在东亚人类进化的序列是连续的,并无受到干扰的迹象。     

Peopling of Sahul: mtDNA variation in aboriginal Australian and Papua New Guinean populations.

We examined genetic affinities of Aboriginal Australian and New Guinean populations by using nucleotide variation in the two hypervariable segments of the mtDNA control region (CR). A total of 318 individuals from highland Papua New Guinea (PNG), coastal PNG, and Aboriginal Australian populations were typed with a panel of 29 sequence-specific oligonucleotide (SSO) probes. The SSO-probe panel included five new probes that were used to type an additional 1,037 individuals from several Asian populations. The SSO-type data guided the selection of 78 individuals from Australia and east Indonesia for CR sequencing. A gene tree of these CR sequences, combined with published sequences from worldwide populations, contains two previously identified highland PNG clusters that do not include any Aboriginal Australians; the highland PNG clusters have coalescent time estimates of approximately 80,000 and 122,000 years ago, suggesting ancient isolation and genetic drift. SSO-type data indicate that 84% of the sample of PNG highlander mtDNA belong to these two clusters. In contrast, the Aboriginal Australian sequences are intermingled throughout the tree and cluster with sequences from multiple populations. Phylogenetic and multidimensional-scaling analyses of CR sequences and SSO types split PNG highland and Aboriginal Australian populations and link Aboriginal Australian populations with populations from the subcontinent of India. These mtDNA results do not support a close relationship between Aboriginal Australian and PNG populations but instead suggest multiple migrations in the peopling of Sahul.     

Relative placement of the mandibular fossa in great apes and humans

Several researchers have investigated, or commented on, the relative placement of the hominin mandibular fossa with regard to brain expansion and masticatory function. Two confounding factors are identified in this previous work. First, a number of different measurement techniques have been applied, confusing comparisons between studies. Second, the effects of squamous thickening due to temporal bone pneumatization are shown to influence measurements based relative to the ectocranial margin of the skull.To investigate the influence of these factors, a sample of adult human (n=12), chimpanzee (n=12), gorilla (n=15), and orang-utan (n=8) skulls from the Cleveland Museum of Natural History, University of Wisconsin Zoology Museum, and University of Wisconsin Anthropology collections, were CT scanned. Coronal scans were horizontally aligned and measured on a personal computer using ImageJ (NIH). To identify fossa placement, fossa breadth was measured as the projected distance in the coronal plane between the tip of the entoglenoid to lateral margin of the articular surface. A second distance, from the tip of the entoglenoid to a sagittal plane, tangent to the lateralmost margin of the endocranial surface was taken to indicate the extent of medial placement of the fossa. By eliminating the influence of pneumatization, these data unambiguously confirmed the medial placement of the human fossa and show all great apes as having a laterally placed fossa. Similar measurements on three fossil hominins, KNM-BC 1 (Homo sp. indet.), OH 5 and KNM-ER 23000 (Paranthropus boisei) demonstrate that, while all specimens demonstrate a broad fossa, only KNM-BC 1 is characterized by a relatively medial placement while the latter two display lateral placement.     

Albumin — vitamin D-binding protein haplotypes in Asian-Pacific populations

Summary We have determined the various haplotypic combinations between alleles as well as restriction fragment length polymorphisms of two linked genetic markers, albumin and vitamin D-binding protein or group-specific component, in a number of Asian-Pacific populations. Using the partial maximum likelihood method, we constructed a phylogenetic network from the haplotype frequencies to assess relationships among the populations sampled. No systematic linkage disequilibrium was detected between most of the combinations, suggesting a lack of operation of any selection pressure at the two loci. The phylogenetic analysis confirmed the known interrelationships among various populations in the Asian-Pacific region. The Australian aborigines clustered closely with the non-Austronesian-speaking highlanders from Papua New Guinea, as expected. Similarly, the Austronesian-speaking Polynesians, Micronesians, and the Southeast Asians branched off together as a separate group. The position of the Austronesian-speaking Tolais from New Britain with respect to other populations from the Southwest Pacific was anomalous. The Tolais revealed a strong affinity with the Australian aborigines, which is inexplicable. The populations from China formed a tight cluster with other populations from the Asian-Pacific region. Genetic interrelationships of these populations with the white Australians were remote, which is in accordance with the known affinities of various human racial groups.     

Artificial cranial deformation and fossil Australians revisited

Based on cranial characters shared by Homo erectus in Java and Homo sapiens in Australia, Australasia is widely considered the strongest case for a regional origin of modern humans. However, artificial vault deformation has been suggested to be the cause of "archaic" characters such as frontal recession in key fossil Australian crania. We use log-log plots of cranial arc versus chord measurements and we score nonmetric traits often thought to be associated with artificial deformation to make systematic comparisons across groups and deformation types to identify universal consequences of artificial deformation. Based on our large comparative sample (n = 588) apparatus-deformed crania have flatter frontals and occipitals and usually more angulated parietals in the sagittal plane than undeformed crania, regardless of deformation type. Fossil Australian samples exhibit evidence of both undeformed and deformed individuals. The sample from Coobool Creek provides evidence that undeformed individuals had more rounded frontals than recent Australians. However, many individuals from Coobool Creek, Kow Swamp, and Nacurrie exhibit modification of one or more cranial contours. The Kow Swamp individuals in particular plot with deformed crania from all regions. In addition, the frequency of hyperostotic traits such as bregmatic eminence, metopic and sagittal keels in H. sapiens is influenced by both artificial deformation and pathological hypervascularity/hyperostosis. Thus it is unwise to use cranial contours and these nonmetric traits to infer genetic relatedness between Fossil Australians and Indonesian H. erectus.     

Dental size variation in the Atapuerca-SH Middle Pleistocene hominids

The Middle Pleistocene Atapuerca-Sima de los Huesos (SH) site in Spain has yielded the largest sample of fossil hominids so far found from a single site and belonging to the same biological population. The SH dental sample includes a total of 452 permanent and deciduous teeth, representing a minimum of 27 individuals. We present a study of the dental size variation in these hominids, based on the analysis of the mandibular permanent dentition: lateral incisors, n=29; canines, n=27; third premolars, n=30; fourth premolars, n=34; first molars, n=38; second molars, n=38. We have obtained the buccolingual diameter and the crown area (measured on occlusal photographs) of these teeth, and used the bootstrap method to assess the amount of variation in the SH sample compared with the variation of a modern human sample from the Museu Antropologico of the Universidade of Coimbra (Portugal). The SH hominids have, in general terms, a dental size variation higher than that of the modern human sample. The analysis is especially conclusive for the canines. Furthermore, we have estimated the degree of sexual dimorphism of the SH sample by obtaining male and female dental subsamples by means of sexing the large sample of SH mandibular specimens. We obtained the index of sexual dimorphism (ISD=male mean/female mean) and the values were compared with those obtained from the sexed modern human sample from Coimbra, and with data found in the literature concerning several recent human populations. In all tooth classes the ISD of the SH hominids was higher than that of modern humans, but the differences were generally modest, except for the canines, thus suggesting that canine size sexual dimorphism in Homo heidelbergensis was probably greater than that of modern humans. Since the approach of sexing fossil specimens has some obvious limitations, these results should be assessed with caution. Additional data from SH and other European Middle Pleistocene sites would be necessary to test this hypothesis.     

Environment and morphology in Australian Aborigines: a re-analysis of the Birdsell database

Pursuant to his major research interest in the cultural ecology of hunter-gatherers, Birdsell collected an unparalleled body of phenotypic data on Aboriginal Australians during the mid twentieth century. Birdsell did not explicitly relate the geographic patterning in his data to Australia's climatic variation, instead arguing that the observable differences between groups reflect multiple origins of Australian Aborigines. In this article, bivariate correlation and multivariate analyses demonstrate statistically significant associations between climatic variables and the body build of Australians that are consistent with the theoretical expectations of Bergmann's and Allen's rules. While Australian Aborigines in comparison to Eurasian and New World populations can be generally described as long-headed, linear in build, and characterized by elongated distal limbs, the variation in this morphological pattern across the continent evidently reflects biological adaptation to local Holocene climates. These results add to a growing body of evidence for the role of environmental selection in the development of modern human variation.