Molecular analysis of Neanderthal DNA from the northern Caucasus

189

The taxonomic status of Neanderthals lies at the center of the modern human origins debate. Proponents of the single-origin model often view this group as a distinct species with little or no contribution to the evolution of modern humans. Adherents to the regional continuity model consider Neanderthals a subspecies or population of Homo sapiens, which contributed significantly to the evolution of early modern Europeans. Paleontologists generally agree that fossil species should be equivalent to extant ones in the amount of their morphological variation. E ver since Neanderthals were first discovered in the 19th century, their specific status and contribution to modern human evolution have been debated. The current controversy centers around two contrasting models for modern human evolution (1, 2): the single-origin theory, which frequently views modern humans as a new species arising relatively recently in Africa and replacing indigenous archaic populations around the world; and the regional-continuity model, in which archaic populations contributed to the evolution of modern peoples in each geographic area. Directly tied to these two models is the status of Neanderthals as a distinct species or as a subspecies of Homo sapiens at least partially ancestral to modern Europeans. The morphological differences between Neanderthals and modern humans are well documented; however, their magnitude can be meaningfully assessed only within the broader context of primate species variability. Here we used 12 extant catarrhine species as models of 3D craniofacial shape variation. Our sample comprised 1,089 specimens, including modern humans, African apes, and eight species of Old World monkeys. The morphological distinctiveness of Neanderthals from modern humans, as represented by our data, was then compared to the differences between pairs of model taxa.Although there is consensus that species in paleontology should be equivalent to living ones in the variation that they accommodate (3, 4), there is no absolute degree of difference that defines species boundaries across taxa (5), making the choice of models critical. Recent studies have supported a specific status for Neanderthals based on analogy to chimpanzee (6) and hybridizing Sulawesi macaque (7) craniofacial morphology. These models may not be the most relevant: chimpanzees differ in their geographic distribution and ecology from Pleistocene humans, whereas the Sulawesi macaques are not representative of the full geographic and ecological range of Macaca. Modern humans are the most appropriate phylogenetic model for Neanderthals but can provide only intraspecific measures of variation. As the closest living relatives to modern humans, the African apes are often used as models for hominin species (4, 8). Yet these two genera comprise only three species, all of which are ecologically distinct from Pleistocene humans. Papionin monkeys, although more distantly related, are often considered (9-11) similar to hominins in their ecology and population structure, and their evo...

Section: Resultssupporting

confidence: 54%

Neanderthal taxonomy reconsidered: Implications of 3D primate models of intra- and interspecific differences

Harvati

Frost

McNulty

2004

189

“…Because the SH hominids are not on the direct evolutionary line that gave rise to our own species, but form part of the Neandertal evolutionary lineage (19)(20)(21), it is conceivable that this condition was already present in the last common ancestor of modern humans and Neandertals. Analysis of Neandertal mtDNA suggests that this last common ancestor probably lived at least 500 thousand years ago (40)(41)(42), and it has been argued to be represented among the 800,000-year-old fossils from the TD6 level at the site of Gran Dolina (Sierra de Atapuerca, Spain) attributed to the species Homo antecessor (43,44).…”

Section: Resultsmentioning

confidence: 99%

Auditory capacities in Middle Pleistocene humans from the Sierra de Atapuerca in Spain

Martı́nez

Rosa

Arsuaga

et al. 2004

142

Human hearing differs from that of chimpanzees and most other anthropoids in maintaining a relatively high sensitivity from 2 kHz up to 4 kHz, a region that contains relevant acoustic information in spoken language. Knowledge of the auditory capacities in human fossil ancestors could greatly enhance the understanding of when this human pattern emerged during the course of our evolutionary history. Here we use a comprehensive physical model to analyze the influence of skeletal structures on the acoustic filtering of the outer and middle ears in five fossil human specimens from the Middle Pleistocene site of the Sima de los Huesos in the Sierra de Atapuerca of Spain. Our results show that the skeletal anatomy in these hominids is compatible with a human-like pattern of sound power transmission through the outer and middle ear at frequencies up to 5 kHz, suggesting that they already had auditory capacities similar to those of living humans in this frequency range.K nowledge about the sensory capabilities of past life forms could greatly enhance our understanding of the adaptations and lifeways in extinct organisms. Audition is the most readily accessible in fossils because it is based primarily in physical properties that can be approached through their skeletal structures (1). Recently, the possibility to analyze auditory capacities in fossil species has been highlighted as one of the major challenges in modern vertebrate paleontology, particularly since the advent of computed tomography (CT)-based analyses (2).The recent publication of a detailed comparison of the human and chimpanzee genomes has highlighted several genes involved with hearing that appear to have undergone adaptive evolutionary changes in the human lineage (3). The authors have suggested that these changes could be related with the acquisition of hearing acuity necessary for understanding spoken language, and they emphasize the importance of further research into hearing differences between humans and chimpanzees (3). At least one of the human genes mentioned as having undergone adaptive evolutionary change (EYA1) is related to the development of the outer and middle ear (4, 5). These results are compatible with the known differences in the anatomical structures of the outer and middle ear in chimpanzees and ourselves (6, 7).As might be expected from these genetic and anatomical data, the empirical studies of chimpanzee hearing capabilities also show clear differences with human hearing. Chimpanzee audiograms (8, 9) show a W-shaped pattern characterized by two peaks of high sensitivity at Ϸ1 kHz and 8 kHz, respectively, and a relative loss of sensitivity in the midrange frequencies (between 2 and 4 kHz). Of course, this relative loss does not mean that chimpanzees cannot hear in the midrange frequencies, but rather that they are adapted to hear best at Ϸ1 kHz and 8 kHz. It is interesting to note that the species-specific pant-hoots regularly emitted by wild chimpanzees to communicate with conspecifics over long distances concentrate the acoustic ...

“…The best support for this hypothesis comes from genetic evidence for an African origin of extant human populations between 100,000 and 200,000 years ago, and for divergence between humans and Neanderthals about 500,000-600,000 years ago (10)(11)(12). Testing this hypothesis by using cranial features, however, is a challenge because of the substantial integration that occurs among the various semi-independent units of the cranium (13,14).…”

mentioning

confidence: 99%

The evolution and development of cranial form in Homo sapiens

Lieberman

McBratney

Krovitz

2002

384

317

Despite much data, there is no unanimity over how to define Homo sapiens in the fossil record. Here, we examine cranial variation among Pleistocene and recent human fossils by using a model of cranial growth to identify unique derived features (autapomorphies) that reliably distinguish fossils attributed to ''anatomically modern'' H. sapiens (AMHS) from those attributed to various taxa of ''archaic'' Homo spp. (AH) and to test hypotheses about the changes in cranial development that underlie the origin of modern human cranial form. In terms of pattern, AMHS crania are uniquely characterized by two general structural autapomorphies: facial retraction and neurocranial globularity. Morphometric analysis of the ontogeny of these autapomorphies indicates that the developmental changes that led to modern human cranial form derive from a combination of shifts in cranial base angle, cranial fossae length and width, and facial length. These morphological changes, some of which may have occurred because of relative size increases in the temporal and possibly the frontal lobes, occur early in ontogeny, and their effects on facial retraction and neurocranial globularity discriminate AMHS from AH crania. The existence of these autapomorphies supports the hypothesis that AMHS is a distinct species from taxa of ''archaic'' Homo (e.g., Homo neanderthalensis).