Journal abstracts 2011
Mathematical accuracy of Aztec land surveys assessed from records in the Codex Vergara
María del Carmen Jorgea, Barbara J. Williamsb, C. E. Garza-Humea and Arturo Olveraa. PNAS 108(37): 15053-15057
Land surveying in ancient states is documented not only for Eurasia but also for the Americas, amply attested by two Acolhua–Aztec pictorial manuscripts from the Valley of Mexico. The Codex Vergara and the Códice de Santa María Asunción consist of hundreds of drawings of agricultural fields that uniquely record surface areas as well as perimeter measurements. A previous study of the Codex Vergara examines how Acolhua–Aztecs determined field area by reconstructing their calculation procedures. Here we evaluate the accuracy of their area values using modern mathematics. The findings verify the overall mathematical validity of the codex records. Three-quarters of the areas are within 5% of the maximum possible value, and 85% are within 10%, which compares well with reported errors by Western surveyors that postdate Aztec–Acolhua work by several centuries.
An earlier origin for the Acheulian
Christopher J. Lepre, Helene Roche, Dennis V. Kent, Sonia Harmand, Rhonda L. Quinn, Jean-Philippe Brugal, Pierre-Jean Texier, Arnaud Lenoble and Craig S. Feibel. Nature 477: 82-85
The Acheulian is one of the first defined prehistoric technocomplexes
and is characterized by shaped bifacial stone tools.
It probably originated in Africa, spreading to Europe and Asia
perhaps as early as 1 million years (Myr) ago. The origin of
the Acheulian is thought to have closely coincided with major
changes in human brain evolution, allowing for further technological
developments. Nonetheless, the emergence of the Acheulian
remains unclear because well-dated sites older than 1.4 Myr ago are
scarce. Here we report on the lithic assemblage and geological context
for the Kokiselei archaeological site fromthe Nachukui formation(
West Turkana,Kenya) that bears characteristic early Acheulian
tools and pushes the first appearance datumfor this stone-age technology
back to 1.76 Myr ago. Moreover, co-occurrence of Oldowan
and Acheulian artefacts at the Kokiselei site complex indicates that
the two technologies are notmutually exclusive time-successive components
of an evolving cultural lineage, and suggests that the
Acheulian was either imported from another location yet to be identified
or originated from Oldowan hominins at this vicinity. In
either case, the Acheulian did not accompany the first human dispersal
from Africa despite being available at the time. This may
indicate that multiple groups of hominins distinguished by separate
stone-tool-making behaviours and dispersal strategies coexisted in
Africa at 1.76 Myr ago.
Biogeochemical inferences of mobility of early Holocene fisher-foragers from the Southern Sahara Desert
Stojanowski, C., Knudson, K. American Journal of Physical Anthropology 146(1): 49-61
North Africa is increasingly seen as an important context for understanding modern human evolution and reconstructing biocultural adaptations. The Sahara, in particular, witnessed a fluorescence of hunter-gatherer settlement at the onset of the Holocene after an extended occupational hiatus. Subsequent subsistence changes through the Holocene are contrary to those documented in other areas where mobile foraging gave way to settled agricultural village life. In North Africa, extractive fishing and hunting was supplanted by cattle and caprine pastoralism under deteriorating climatic conditions. Therefore, the initial stage of food production in North Africa witnessed a likely increase in mobility. However, there are few studies of paleomobility in Early Holocene hunter-gatherer Saharan populations and the degree of mobility is generally assumed. Here, we present radiogenic strontium isotope ratios from Early Holocene fisher-forager peoples from the site of Gobero, central Niger, southern Sahara Desert. Data indicate a relatively homogeneous radiogenic strontium isotope signature for this hunter-gather population with limited variability exhibited throughout the life course or among different individuals. Although the overall signature was local, some variation in the radiogenic strontium isotope data likely reflects transhumance into the nearby Aïr Massif. Data from Gobero were significantly less variable than in other worldwide hunter-gatherer populations, including those thought to be fairly sedentary. Strontium data from Gobero were also significantly different from contemporaneous sites in southwestern Libya. These patterns are discussed with respect to archaeological models of community organization and technological evolution.
Special Collection 2011: Australopithecus sediba
The transition in human ancestry from Australopithecus, the genus that existed for 2 million years before Homo, has been enigmatic. A key fossil from near the time of this transition is Australopithecus sediba, which is represented by several specimens discovered in a cave in South Africa. Five Reports in the 9 September 2011 Science, as well as a related News Focus package and podcast interview, discuss important features of the A. sediba fossils, including some that are not well preserved in other similar hominid remains.
Sperm Methylation Profiles Reveal Features of Epigenetic Inheritance and Evolution in Primates
Antoine Molaro, Emily Hodges, Fang Fang, Qiang Song, W. Richard McCombie, Gregory J. Hannon, Andrew D. Smith. Cell 146(6): 1029-1041
During germ cell and preimplantation development, mammalian cells undergo nearly complete reprogramming of DNA methylation patterns. We profiled the methylomes of human and chimp sperm as a basis for comparison to methylation patterns of ESCs. Although the majority of promoters escape methylation in both ESCs and sperm, the corresponding hypomethylated regions show substantial structural differences. Repeat elements are heavily methylated in both germ and somatic cells; however, retrotransposons from several subfamilies evade methylation more effectively during male germ cell development, whereas other subfamilies show the opposite trend. Comparing methylomes of human and chimp sperm revealed a subset of differentially methylated promoters and strikingly divergent methylation in retrotransposon subfamilies, with an evolutionary impact that is apparent in the underlying genomic sequence. Thus, the features that determine DNA methylation patterns differ between male germ cells and somatic cells, and elements of these features have diverged between humans and chimpanzees.
Genetic evidence for archaic admixture in Africa
Michael F. Hammera, August E. Woernera, Fernando L. Mendezb, Joseph C. Watkinsc, and Jeffrey D. Walld. PNAS 108 (37) 15123-15128
A long-debated question concerns the fate of archaic forms of the genus Homo: did they go extinct without interbreeding with anatomically modern humans, or are their genes present in contemporary populations? This question is typically focused on the genetic contribution of archaic forms outside of Africa. Here we use DNA sequence data gathered from 61 noncoding autosomal regions in a sample of three sub-Saharan African populations (Mandenka, Biaka, and San) to test models of African archaic admixture. We use two complementary approximate-likelihood approaches and a model of human evolution that involves recent population structure, with and without gene flow from an archaic population. Extensive simulation results reject the null model of no admixture and allow us to infer that contemporary African populations contain a small proportion of genetic material (˜2%) that introgressed ˜35 kya from an archaic population that split from the ancestors of anatomically modern humans ˜700 kya. Three candidate regions showing deep haplotype divergence, unusual patterns of linkage disequilibrium, and small basal clade size are identified and the distributions of introgressive haplotypes surveyed in a sample of populations from across sub-Saharan Africa. One candidate locus with an unusual segment of DNA that extends for >31 kb on chromosome 4 seems to have introgressed into modern Africans from a now-extinct taxon that may have lived in central Africa. Taken together our results suggest that polymorphisms present in extant populations introgressed via relatively recent interbreeding with hominin forms that diverged from the ancestors of modern humans in the Lower-Middle Pleistocene.
The Later Stone Age Calvaria from Iwo Eleru, Nigeria: Morphology and Chronology
Katerina Harvati, Chris Stringer, Rainer Grün, Maxime Aubert, Philip Allsworth-Jones, Caleb Adebayo Folorunso. PLoS One 6(9)
In recent years the Later Stone Age has been redated to a much deeper time depth than previously thought. At the same time, human remains from this time period are scarce in Africa, and even rarer in West Africa. The Iwo Eleru burial is one of the few human skeletal remains associated with Later Stone Age artifacts in that region with a proposed Pleistocene date. We undertook a morphometric reanalysis of this cranium in order to better assess its affinities. We also conducted Uranium-series dating to re-evaluate its chronology.
Mesolithic Site Formation and Palaeoenvironment Along the White Nile (Central Sudan)
Sandro Salvatori, Donatella Usai and Andrea Zerboni. African Archaeological Review 28(3)
The Mesolithic period represents a key stage in the human history of Sudan, but its complexity is not yet fully understood. Since the beginning of prehistoric research in this region, efforts were made to understand Mesolithic site formation processes and post-depositional disturbances. Responsibility for the destruction of most Mesolithic sites’ deposits rests mainly on later use of the ancient mound-like settlements as burial places by Meroitic and post-Meroitic people. Excavations at several sites in the El Salha and Al Khiday areas (White Nile, south of Omdurman) have provided recent progress in our knowledge of Mesolithic living structures in their palaeoenvironmental contexts. Detailed stratigraphic and geoarchaeological investigations enabled us to distinguish, within the sequences identified at excavated mounds, the existence of basal archaeological strata still in situ that had remained unaffected by subsequent anthropogenic disturbances and to understand the functional aspects of several archaeological features associated with Mesolithic living floors. This offers the opportunity to reassess the Mesolithic cultural sequence in the region and reconsider some statements on the economic and social aspects of Mesolithic life and landscape exploitation strategies.
The Upper Palaeolithic Lithic Industry of Nazlet Khater 4 (Egypt): Implications for the Stone Age/Palaeolithic of Northeastern Africa
Alice Leplongeon and David Pleurdeau. African Archaeological Review 28(3)
Between Marine Isotope Stage (MIS) 4 and 2, Northeast Africa witnessed migrations of Homo
sapiens into Eurasia. Within the context of the aridification of the Sahara, the Nile Valley probably offered a very attractive corridor into Eurasia. This region and this period are therefore central for the (pre)history of the out-of-Africa peopling of modern humans. However, there are very few sites from the beginning of the Upper Palaeolithic that document these migration events. In Egypt, the site of Nazlet Khater 4 (NK4), which is related to ancient H. sapiens quarrying activities, is one of them. Its lithic assemblage shows an important laminar component, and this, associated with its chronological position (ca. 33 ka), means that the site is the most ancient Upper Palaeolithic sites of this region. The detailed study of the Nazlet Khater 4 lithic material shows that blade production (volumetric reduction) is also associated with flake production (surface reduction). This technological duality addresses the issue of direct attribution of NK4 to the Upper Palaeolithic.
CT-based study of internal structure of the anterior pillar in extinct hominins and its implications for the phylogeny of robust Australopithecus
Brian A. Villmoarea and William H. Kimbel. PNAS September 19
The phylogeny of the early African hominins has long been confounded by contrasting interpretations of midfacial structure. In particular, the anterior pillar, an externally prominent bony column running vertically alongside the nasal aperture, has been identified as a homology of South African species Australopithecus africanus and Australopithecus robustus. If the anterior pillar is a true synapomorphy of these two species, the evidence for a southern African clade of Australopithecus would be strengthened, and support would be given to the phylogenetic hypothesis of an independent origin for eastern and southern African “robust” australopith clades. Analyses of CT data, however, show that the internal structure of the circumnasal region is strikingly different in the two South African australopith species. In A. africanus the anterior pillar is a hollow column of cortical bone, whereas in A. robustus it is a column of dense trabecular bone. Although Australopithecus boisei usually lacks an external pillar, it has internal morphology identical to that seen in A. robustus. This result supports the monophyly of the “robust” australopiths and suggests that the external similarities seen in the South African species are the result of parallel evolution.
Denisova Admixture and the First Modern Human Dispersals into Southeast Asia and Oceania
David Reich et al. Cell 22 September
It has recently been shown that ancestors of New Guineans and Bougainville Islanders have inherited a proportion of their ancestry from Denisovans, an archaic hominin group from Siberia. However, only a sparse sampling of populations from Southeast Asia and Oceania were analyzed. Here, we quantify Denisova admixture in 33 additional populations from Asia and Oceania. Aboriginal Australians, Near Oceanians, Polynesians, Fijians, east Indonesians, and Mamanwa Negrito group from the Philippines) have all inherited genetic material from Denisovans, but mainland East Asians, western Indonesians, Jehai (a Negrito group from Malaysia), and Onge (a Negrito group from the Andaman Islands) have not. These results indicate that Denisova gene flow occurred into the common ancestors of New Guineans, Australians, and Mamanwa but not into the ancestors of the Jehai and Onge and suggest that relatives of present-day East Asians were not in Southeast Asia when the Denisova gene flow occurred. Our finding that descendants of the earliest inhabitants of Southeast Asia do not all harbor Denisova admixture is inconsistent with a history in which the Denisova interbreeding occurred in mainland Asia and then spread over Southeast Asia, leading to all its earliest modern human inhabitants. Instead, the data can be most parsimoniously explained if the Denisova gene flow occurred in Southeast Asia itself. Thus, archaic Denisovans must have lived over an extraordinarily broad geographic and ecological range, from Siberia to tropical Asia.
An Aboriginal Australian Genome Reveals Separate Human Dispersals into Asia
Morten Rasmussen et al. Science Published Online September 22
We present an Aboriginal Australian genomic sequence obtained from a 100-year-old lock of hair donated by an Aboriginal man from southern Western Australia in the early 20th century. We detect no evidence of European admixture and estimate contamination levels to be below 0.5%. We show that Aboriginal Australians are descendants of an early human dispersal into eastern Asia, possibly 62,000 to 75,000 years ago. This dispersal is separate from the one that gave rise to modern Asians 25,000 to 38,000 years ago. We also find evidence of gene flow between populations of the two dispersal waves prior to the divergence of Native Americans from modern Asian ancestors. Our findings support the hypothesis that present-day Aboriginal Australians descend from the earliest humans to occupy Australia, likely representing one of the oldest continuous populations outside Africa.