Body size and body shape in early hominins - implications of the Gona pelvis.
ABSTRACT Discovery of the first complete Early Pleistocene hominin pelvis, Gona BSN49/P27, attributed to Homo erectus, raises a number of issues regarding early hominin body size and shape variation. Here, acetabular breadth, femoral head breadth, and body mass calculated from femoral head breadth are compared in 37 early hominin (6.0-0.26 Ma) specimens, including BSN49/P27. Acetabular and estimated femoral head sizes in the Gona specimen fall close to the means for non-Homo specimens (Orrorin tugenesis, Australopithecus africanus, Paranthropus robustus), and well below the ranges of all previously described Early and Middle Pleistocene Homo specimens. The Gona specimen has an estimated body mass of 33.2kg, close to the mean for the non-Homo sample (34.1kg, range 24-51.5kg, n=19) and far outside the range for any previously known Homo specimen (mean=70.5kg; range 52-82kg, n=17). Inclusion of the Gona specimen within H. erectus increases inferred sexual dimorphism in body mass in this taxon to a level greater than that observed here for any other hominin taxon, and increases variation in body mass within H. erectus females to a level much greater than that observed for any living primate species. This raises questions regarding the taxonomic attribution of the Gona specimen. When considered within the context of overall variation in body breadth among early hominins, the mediolaterally very wide Gona pelvis fits within the distribution of other lower latitude Early and Middle Pleistocene specimens, and below that of higher latitude specimens. Thus, ecogeographic variation in body breadth was present among earlier hominins as it is in living humans. The increased M-L pelvic breadth in all earlier hominins relative to modern humans is related to an increase in ellipticity of the birth canal, possibly as a result of a non-rotational birth mechanism that was common to both australopithecines and archaic Homo.
Article: Early Homo: Who, When, and Where[Show abstract] [Hide abstract]
ABSTRACT: The origin of Homo is argued to entail niche differentiation resulting from increasing terrestriality and dietary breadth relative to the better known species of Australopithecus (A. afarensis, A. anamensis, A. africanus). I review the fossil evidence from ∼2.5 to 1.5 Ma in light of new finds and analyses that challenge previous inferences. Minimally, three cranial morphs of early Homo (including Homo erectus) exist in eastern Africa (1.9–1.4 Ma), with at least two in southern Africa. Because of taphonomic damage to the type specimen of Homo habilis, in East Africa two species with different masticatory adaptations are better identified by their main specimen (i.e., the 1813 group and the 1470 group) rather than a species name. Until recently, the 1470 group comprised a single specimen. South African early Homo are likely distinct from these groups. Together, contemporary early H. erectus and early Homo are bigger than Australopithecus (∼30%). Early H. erectus (including recently discovered small specimens) is larger than non-erectus Homo (∼15%–25%), but their size ranges overlap. All early Homo are likely to exhibit substantial sexual dimorphism. Early H. erectus is less “modern” and its regional variation in size more substantial than previously allowed. These findings form the baseline for understanding the origin of the genus.Current Anthropology 12/2012; 53. DOI:10.1086/667695 · 2.93 Impact Factor
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ABSTRACT: Since the 1984 discovery of the Nariokotome Homo erectus/Homo ergaster skeleton, it has been almost axiomatic that the emergence of Homo (sensu stricto) was characterized by an increase in body size to the modern human condition and an autapomorphic shift in body proportions to those found today. This was linked to a behavioral shift toward more intensive carnivory and wider ranging in the genus Homo. Recent fossil discoveries and reanalysis of the Nariokotome skeleton suggest a more complex evolutionary pattern. While early Homo tend to be larger than Australopithecus/Paranthropus, they were shorter on average than people today. Reanalysis of the Nariokotome pelvis along with the discovery of additional early and middle Pleistocene pelves indicate that a narrow bi-iliac (pelvic) breadth is an autapomorphy specific to Homo sapiens. Likewise, it appears that at least some early Homo (even those referred to H. ergaster/H. erectus) were characterized by higher humero-femoral indices than the H. sapiens average. All these data suggest a pattern of mosaic postcranial evolution in Homo with implications for the increased ranging/carnivory model of the origin of Homo as well as for which species are included within the Homo hypodigm.Current Anthropology 12/2012; 53. DOI:10.1086/667360 · 2.93 Impact Factor
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ABSTRACT: A high level of encephalization is critical to the human adaptive niche and emerged among hominins over the course of the past 2 Myr. Evolving larger brains required important adaptive adjustments, in particular regarding energy allocation and life history. These adaptations included a relatively small brain at birth and a protracted growth of highly dependent offspring within a complex social environment. In turn, the extended period of growth and delayed maturation of the brain structures of humans contribute to their cognitive complexity. The current palaeoanthropological evidence shows that, regarding life history and brain ontogeny, the Pleistocene hominin taxa display different patterns and that one cannot simply contrast an 'ape-model' to a 'human-model'. Large-brained hominins such as Upper Pleistocene Neandertals have evolved along their own evolutionary pathway and can be distinguished from modern humans in terms of growth pattern and brain development. The life-history pattern and brain ontogeny of extant humans emerged only recently in the course of human evolution. © 2015 The Author(s) Published by the Royal Society. All rights reserved.Philosophical Transactions of The Royal Society B Biological Sciences 03/2015; 370(1663). DOI:10.1098/rstb.2014.0062 · 6.31 Impact Factor