Publications by authors named "Christian A Tryon"

18 Publications

  • Page 1 of 1

Human burials at the Kisese II rockshelter, Tanzania.

Am J Phys Anthropol 2021 May 21;175(1):187-200. Epub 2021 Feb 21.

Institute of Human Origins, School of Human Evolution and Social Change, Arizona State University, Tempe, Arizona, USA.

Objectives: The Late Pleistocene and early Holocene in eastern Africa are associated with complex evolutionary and demographic processes that contributed to the population variability observed in the region today. However, there are relatively few human skeletal remains from this time period. Here we describe six individuals from the Kisese II rockshelter in Tanzania that were excavated in 1956, present a radiocarbon date for one of the individuals, and compare craniodental morphological diversity among eastern African populations.

Materials And Methods: This study used standard biometric analyses to assess the age, sex, and stature of the Kisese II individuals. Eastern African craniodental morphological variation was assessed using measures of dental size and a subset of Howells' cranial measurements for the Kisese II individuals as well as early Holocene, early pastoralist, Pastoral Neolithic, and modern African individuals.

Results: Our results suggest a minimum of six individuals from the Kisese II collections with two adults and four juveniles. While the dating for most of the burials is uncertain, one individual is directly radiocarbon dated to ~7.1 ka indicating that at least one burial is early Holocene in age. Craniodental metric comparisons indicate that the Kisese II individuals extend the amount of human morphological diversity among Holocene eastern Africans.

Conclusions: Our findings contribute to a growing body of evidence that Late Pleistocene and early Holocene eastern Africans exhibited relatively high amounts of morphological diversity. However, the Kisese II individuals suggest morphological similarity at localized sites potentially supporting increased regionalization during the early Holocene.
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http://dx.doi.org/10.1002/ajpa.24253DOI Listing
May 2021

A Late Pleistocene human humerus from Rusinga Island, Lake Victoria, Kenya.

J Hum Evol 2020 09 8;146:102855. Epub 2020 Aug 8.

Department of Anthropology, University of Connecticut, 354 Mansfield Road, Storrs, CT, 06269, USA.

In 2010, a hominin right humerus fragment (KNM-RU 58330) was surface collected in a small gully at Nyamita North in the Late Pleistocene Wasiriya Beds of Rusinga Island, Kenya. A combination of stratigraphic and geochronological evidence suggests the specimen is likely between ∼49 and 36 ka in age. The associated fauna is diverse and dominated by semiarid grassland taxa. The small sample of associated Middle Stone Age artifacts includes Levallois flakes, cores, and retouched points. The 139 mm humeral fragment preserves the shaft from distal to the lesser tubercle to 14 mm below the distal end of the weakly projecting deltoid tuberosity. Key morphological features include a narrow and weakly marked pectoralis major insertion and a distinctive medial bend in the diaphysis at the deltoid insertion. This bend is unusual among recent human humeri but occurs in a few Late Pleistocene humeri. The dimensions of the distal end of the fragment predict a length of 317.9 ± 16.4 mm based on recent samples of African ancestry. A novel method of predicting humeral length from the distance between the middle of the pectoralis major and the bottom of the deltoid insertion predicts a length of 317.3 mm ± 17.6 mm. Cross-sectional geometry at the midshaft shows a relatively high percentage of cortical bone and a moderate degree of flattening of the shaft. The Nyamita humerus is anatomically modern in its morphology and adds to the small sample of hominins from the Late Pleistocene associated with Middle Stone Age artifacts known from East Africa. It may sample a population closely related to the people of the out-of-Africa migration.
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http://dx.doi.org/10.1016/j.jhevol.2020.102855DOI Listing
September 2020

The Middle/Later Stone Age transition and cultural dynamics of late Pleistocene East Africa.

Evol Anthropol 2019 Sep;28(5):267-282

Department of Anthropology, University of Connecticut, Storrs, Connecticut.

The Middle to Later Stone Age (MSA/LSA) transition is a prominent feature of the African archeological record that began in some places ~30,000-60,000 years ago, historically associated with the origin and/or dispersal of "modern" humans. Unlike the analogous Middle to Upper Paleolithic transition in Eurasia and associated Neanderthal extinction, the African MSA/LSA record remains poorly documented, with its potential role in explaining changes in the behavioral diversity and geographic range of Homo sapiens largely unexplored. I review archeological and biogeographic data from East Africa, show regionally diverse pathways to the MSA/LSA transition, and emphasize the need for analytical approaches that document potential ancestor-descendent relationships visible in the archeological record, needed to assess independent invention, population interaction, dispersal, and other potential mechanisms for behavioral change. Diversity within East Africa underscores the need for regional, rather than continental-scale narratives of the later evolutionary history of H. sapiens.
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http://dx.doi.org/10.1002/evan.21802DOI Listing
September 2019

Archeological evidence for human dispersals around the Mediterranean basin?

Evol Anthropol 2019 Sep 23;28(5):233-235. Epub 2019 Jul 23.

Department of Anthropology, University of Connecticut, Storrs, Connecticut.

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http://dx.doi.org/10.1002/evan.21792DOI Listing
September 2019

Lithic raw material acquisition and use by early Homo sapiens at Skhul, Israel.

J Hum Evol 2019 02 5;127:149-170. Epub 2019 Feb 5.

Department of Anthropology, Harvard University, Peabody Museum of Anthropology, 11 Divinity Ave., Cambridge, MA 02138, USA. Electronic address:

The site of Skhul in Israel has featured prominently in discussions about the early presence of Homo sapiens outside of Africa since its excavation in the 1930s. Until now, attention has been primarily focused on the site's fossil hominins and evidence for symbolic behavior in the form of burials and rare artifacts such as pierced shells and pigment objects. We present here the results of renewed analysis of the lithic artifacts from Skhul drawn from archival collections in the United States, United Kingdom, and Israel. Although lithic artifacts form the majority of the archaeological record from the site, they have rarely been the subject of comprehensive study. Our analyses of raw material selection, use and transport combined with technological analyses of artifact production methods (1) indicate selective transport to the site of large flakes, retouched pieces, and particularly Levallois points from non-local sources, and (2) demonstrate substantial variability in raw material procurement that fails to indicate clear differences in landscape use between H. sapiens and Neanderthals.
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http://dx.doi.org/10.1016/j.jhevol.2018.10.005DOI Listing
February 2019

Did Our Species Evolve in Subdivided Populations across Africa, and Why Does It Matter?

Trends Ecol Evol 2018 08 11;33(8):582-594. Epub 2018 Jul 11.

Laboratoire Évolution & Diversité Biologique (EDB UMR 5174), Université de Toulouse Midi-Pyrénées, CNRS, IRD, UPS. 118 route de Narbonne, Bat 4R1, 31062 Toulouse cedex 9, France; Instituto Gulbenkian de Ciência, P-2780-156, Oeiras, Portugal.

We challenge the view that our species, Homo sapiens, evolved within a single population and/or region of Africa. The chronology and physical diversity of Pleistocene human fossils suggest that morphologically varied populations pertaining to the H. sapiens clade lived throughout Africa. Similarly, the African archaeological record demonstrates the polycentric origin and persistence of regionally distinct Pleistocene material culture in a variety of paleoecological settings. Genetic studies also indicate that present-day population structure within Africa extends to deep times, paralleling a paleoenvironmental record of shifting and fractured habitable zones. We argue that these fields support an emerging view of a highly structured African prehistory that should be considered in human evolutionary inferences, prompting new interpretations, questions, and interdisciplinary research directions.
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http://dx.doi.org/10.1016/j.tree.2018.05.005DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6092560PMC
August 2018

Environmental dynamics during the onset of the Middle Stone Age in eastern Africa.

Science 2018 04 15;360(6384):86-90. Epub 2018 Mar 15.

Department of Geological Sciences, University of Saskatchewan, Saskatoon, SK S7N 5E2, Canada.

Development of the African Middle Stone Age (MSA) before 300,000 years ago raises the question of how environmental change influenced the evolution of behaviors characteristic of early We used temporally well-constrained sedimentological and paleoenvironmental data to investigate environmental dynamics before and after the appearance of the early MSA in the Olorgesailie basin, Kenya. In contrast to the Acheulean archeological record in the same basin, MSA sites are associated with a markedly different faunal community, more pronounced erosion-deposition cycles, tectonic activity, and enhanced wet-dry variability. Aspects of Acheulean technology in this region imply that, as early as 615,000 years ago, greater stone material selectivity and wider resource procurement coincided with an increased pace of land-lake fluctuation, potentially anticipating the adaptability of MSA hominins.
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http://dx.doi.org/10.1126/science.aao2200DOI Listing
April 2018

Middle and Later Stone Age chronology of Kisese II rockshelter (UNESCO World Heritage Kondoa Rock-Art Sites), Tanzania.

PLoS One 2018 28;13(2):e0192029. Epub 2018 Feb 28.

National Museum of Tanzania, Shaaban Robert Street, Dar es Salaam, Tanzania.

The archaeology of East Africa during the last ~65,000 years plays a central role in debates about the origins and dispersal of modern humans, Homo sapiens. Despite the historical importance of the region to these discussions, reliable chronologies for the nature, tempo, and timing of human behavioral changes seen among Middle Stone Age (MSA) and Later Stone Age (LSA) archaeological assemblages are sparse. The Kisese II rockshelter in the Kondoa region of Tanzania, originally excavated in 1956, preserves a ≥ 6-m-thick archaeological succession that spans the MSA/LSA transition, with lithic artifacts such as Levallois and bladelet cores and backed microliths, the recurrent use of red ochre, and >5,000 ostrich eggshell beads and bead fragments. Twenty-nine radiocarbon dates on ostrich eggshell carbonate make Kisese II one of the most robust chronological sequences for understanding archaeological change over the last ~47,000 years in East Africa. In particular, ostrich eggshell beads and backed microliths appear by 46-42 ka cal BP and occur throughout overlying Late Pleistocene and Holocene strata. Changes in lithic technology suggest an MSA/LSA transition that began 39-34.3 ka, with typical LSA technologies in place by the Last Glacial Maximum. The timing of these changes demonstrates the time-transgressive nature of behavioral innovations often linked to the origins of modern humans, even within a single region of Africa.
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http://journals.plos.org/plosone/article?id=10.1371/journal.pone.0192029PLOS
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5830042PMC
March 2018

Evaluating the potential for tactical hunting in the Middle Stone Age: Insights from a bonebed of the extinct bovid, Rusingoryx atopocranion.

J Hum Evol 2017 07 17;108:72-91. Epub 2017 May 17.

Harvard University, Department of Anthropology, Peabody Museum of Archaeology and Ethnology, 11 Divinity Ave., Cambridge, MA 02138, USA.

The foraging behaviors of Middle Stone Age (MSA) early modern humans have largely been based on evidence from well-stratified cave sites in South Africa. Whereas these sites have provided an abundance of data for behavioral reconstruction that are unmatched elsewhere in Africa, they are unlikely to preserve evidence of the diversity of foraging strategies employed by MSA hunters who lived in a variety of ecological and landscape settings across the African continent. Here we describe the results of recent excavations at the open-air site of Bovid Hill at Wakondo, Rusinga Island, Kenya, which yielded 24 in situ MSA artifacts within an assemblage of bones comprised exclusively of the extinct alcelaphin bovid Rusingoryx atopocranion. The excavated faunal assemblage is characterized by a prime-age-dominated mortality profile and includes cut-marked specimens and an associated MSA Levallois blade-based artifact industry recovered from a channel deposit dated to 68 ± 5 ka by optically stimulated luminescence. Taphonomic, geologic, and faunal evidence points to mass exploitation of Rusingoryx by humans at Bovid Hill, which likely represents an initial processing site that was altered post-depositionally by fluvial processes. This site highlights the importance of rivers and streams for mass procurement in an open and seasonal landscape, and provides important new insights into MSA behavioral variability with respect to environmental conditions, site function, and tactical foraging strategies in eastern Africa. Bovid Hill thus joins a growing number of MSA and Middle Paleolithic localities that are suggestive of tactical hunting behaviors and mass capture of gregarious ungulate prey.
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http://dx.doi.org/10.1016/j.jhevol.2016.11.004DOI Listing
July 2017

A demographic perspective on the Middle to Later Stone Age transition from Nasera rockshelter, Tanzania.

Philos Trans R Soc Lond B Biol Sci 2016 07;371(1698)

School of Social Science, University of Queensland, Michie Building (Level 3), Brisbane, Queensland 4072, Australia.

Increased population density is among the proposed drivers of the behavioural changes culminating in the Middle to Later Stone Age (MSA-LSA) transition and human dispersals from East Africa, but reliable archaeological measures of demographic change are lacking. We use Late Pleistocene-Holocene lithic and faunal data from Nasera rockshelter (Tanzania) to show progressive declines in residential mobility-a variable linked to population density-and technological shifts, the latter associated with environmental changes. These data suggest that the MSA-LSA transition is part of a long-term pattern of changes in residential mobility and technology that reflect human responses to increased population density, with dispersals potentially marking a complementary response to larger populations.This article is part of the themed issue 'Major transitions in human evolution'.
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http://dx.doi.org/10.1098/rstb.2015.0238DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4920295PMC
July 2016

Unexpected Convergent Evolution of Nasal Domes between Pleistocene Bovids and Cretaceous Hadrosaur Dinosaurs.

Curr Biol 2016 Feb 4;26(4):503-8. Epub 2016 Feb 4.

Department of Anthropology, Harvard University, Peabody Museum, 11 Divinity Avenue, Cambridge, MA 02138, USA.

The fossil record provides tangible, historical evidence for the mode and operation of evolution across deep time. Striking patterns of convergence are some of the strongest examples of these operations, whereby, over time, similar environmental and/or behavioral pressures precipitate similarity in form and function between disparately related taxa. Here we present fossil evidence for an unexpected convergence between gregarious plant-eating mammals and dinosaurs. Recent excavations of Late Pleistocene deposits on Rusinga Island, Kenya, have uncovered a catastrophic assemblage of the wildebeest-like bovid Rusingoryx atopocranion. Previously known from fragmentary material, these new specimens reveal large, hollow, osseous nasal crests: a craniofacial novelty for mammals that is remarkably comparable to the nasal crests of lambeosaurine hadrosaur dinosaurs. Using adult and juvenile material from this assemblage, as well as computed tomographic imaging, we investigate this convergence from morphological, developmental, functional, and paleoenvironmental perspectives. Our detailed analyses reveal broad parallels between R. atopocranion and basal Lambeosaurinae, suggesting that osseous nasal crests may require a highly specific combination of ontogeny, evolution, and environmental pressures in order to develop.
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http://dx.doi.org/10.1016/j.cub.2015.12.050DOI Listing
February 2016

Paleoenvironmental context of the Middle Stone Age record from Karungu, Lake Victoria Basin, Kenya, and its implications for human and faunal dispersals in East Africa.

J Hum Evol 2015 Jun 13;83:28-45. Epub 2015 Apr 13.

Center for the Advanced Study of Hominid Paleobiology, Department of Anthropology, The George Washington University, Washington, DC 20052, USA.

The opening and closing of the equatorial East African forest belt during the Quaternary is thought to have influenced the biogeographic histories of early modern humans and fauna, although precise details are scarce due to a lack of archaeological and paleontological records associated with paleoenvironmental data. With this in mind, we provide a description and paleoenvironmental reconstruction of the Late Pleistocene Middle Stone Age (MSA) artifact- and fossil-bearing sediments from Karungu, located along the shores of Lake Victoria in western Kenya. Artifacts recovered from surveys and controlled excavations are typologically MSA and include points, blades, and Levallois flakes and cores, as well as obsidian flakes similar in geochemical composition to documented sources near Lake Naivasha (250 km east). A combination of sedimentological, paleontological, and stable isotopic evidence indicates a semi-arid environment characterized by seasonal precipitation and the dominance of C4 grasslands, likely associated with a substantial reduction in Lake Victoria. The well-preserved fossil assemblage indicates that these conditions are associated with the convergence of historically allopatric ungulates from north and south of the equator, in agreement with predictions from genetic observations. Analysis of the East African MSA record reveals previously unrecognized north-south variation in assemblage composition that is consistent with episodes of population fragmentation during phases of limited dispersal potential. The grassland-associated MSA assemblages from Karungu and nearby Rusinga Island are characterized by a combination of artifact types that is more typical of northern sites. This may reflect the dispersal of behavioral repertoires-and perhaps human populations-during a paleoenvironmental phase dominated by grasslands.
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http://dx.doi.org/10.1016/j.jhevol.2015.03.004DOI Listing
June 2015

Stable isotope paleoecology of Late Pleistocene Middle Stone Age humans from the Lake Victoria basin, Kenya.

J Hum Evol 2015 May 21;82:1-14. Epub 2015 Mar 21.

Department of Anthropology, Peabody Museum of Archaeology and Ethnology, Harvard University, 11 Divinity Avenue, Cambridge, MA 02138, USA.

Paleoanthropologists have long argued that environmental pressures played a key role in human evolution. However, our understanding of how these pressures mediated the behavioral and biological diversity of early modern humans and their migration patterns within and out of Africa is limited by a lack of archaeological evidence associated with detailed paleoenvironmental data. Here, we present the first stable isotopic data from paleosols and fauna associated with Middle Stone Age (MSA) sites in East Africa. Late Pleistocene (∼100-45 ka, thousands of years ago) sediments on Rusinga and Mfangano Islands in eastern Lake Victoria (Kenya) preserve a taxonomically diverse, non-analog faunal community associated with MSA artifacts. We analyzed the stable carbon and oxygen isotope composition of paleosol carbonate and organic matter and fossil mammalian tooth enamel, including the first analyses for several extinct bovids such as Rusingoryx atopocranion, Damaliscus hypsodon, and an unnamed impala species. Both paleosol carbonate and organic matter data suggest that local habitats associated with human activities were primarily riverine woodland ecosystems. However, mammalian tooth enamel data indicate that most large-bodied mammals consumed a predominantly C4 diet, suggesting an extensive C4 grassland surrounding these riverine woodlands in the region at the time. These data are consistent with other lines of paleoenvironmental evidence that imply a substantially reduced Lake Victoria at this time, and demonstrate that C4 grasslands were significantly expanded into equatorial Africa compared with their present distribution, which could have facilitated dispersal of human populations and other biotic communities. Our results indicate that early populations of Homo sapiens from the Lake Victoria region exploited locally wooded and well-watered habitats within a larger grassland ecosystem.
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http://dx.doi.org/10.1016/j.jhevol.2014.10.005DOI Listing
May 2015

Late Pleistocene age and archaeological context for the hominin calvaria from GvJm-22 (Lukenya Hill, Kenya).

Proc Natl Acad Sci U S A 2015 Mar 17;112(9):2682-7. Epub 2015 Feb 17.

Department of Human Evolution, Max Planck Institute for Evolutionary Anthropology, D-04103, Leipzig, Germany; and Department of Cell and Developmental Biology, University College London, WC1E 6BT London, United Kingdom.

Kenya National Museums Lukenya Hill Hominid 1 (KNM-LH 1) is a Homo sapiens partial calvaria from site GvJm-22 at Lukenya Hill, Kenya, associated with Later Stone Age (LSA) archaeological deposits. KNM-LH 1 is securely dated to the Late Pleistocene, and samples a time and region important for understanding the origins of modern human diversity. A revised chronology based on 26 accelerator mass spectrometry radiocarbon dates on ostrich eggshells indicates an age range of 23,576-22,887 y B.P. for KNM-LH 1, confirming prior attribution to the Last Glacial Maximum. Additional dates extend the maximum age for archaeological deposits at GvJm-22 to >46,000 y B.P. (>46 kya). These dates are consistent with new analyses identifying both Middle Stone Age and LSA lithic technologies at the site, making GvJm-22 a rare eastern African record of major human behavioral shifts during the Late Pleistocene. Comparative morphometric analyses of the KNM-LH 1 cranium document the temporal and spatial complexity of early modern human morphological variability. Features of cranial shape distinguish KNM-LH 1 and other Middle and Late Pleistocene African fossils from crania of recent Africans and samples from Holocene LSA and European Upper Paleolithic sites.
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http://dx.doi.org/10.1073/pnas.1417909112DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4352791PMC
March 2015

The environmental context for the origins of modern human diversity: a synthesis of regional variability in African climate 150,000-30,000 years ago.

J Hum Evol 2012 May 17;62(5):563-92. Epub 2012 Apr 17.

Department of Geosciences, University of Arizona, Tucson, AZ 85712, USA.

We synthesize African paleoclimate from 150 to 30 ka (thousand years ago) using 85 diverse datasets at a regional scale, testing for coherence with North Atlantic glacial/interglacial phases and northern and southern hemisphere insolation cycles. Two major determinants of circum-African climate variability over this time period are supported by principal components analysis: North Atlantic sea surface temperature (SST) variations and local insolation maxima. North Atlantic SSTs correlated with the variability found in most circum-African SST records, whereas the variability of the majority of terrestrial temperature and precipitation records is explained by local insolation maxima, particularly at times when solar radiation was intense and highly variable (e.g., 150-75 ka). We demonstrate that climates varied with latitude, such that periods of relatively increased aridity or humidity were asynchronous across the northern, eastern, tropical and southern portions of Africa. Comparisons of the archaeological, fossil, or genetic records with generalized patterns of environmental change based solely on northern hemisphere glacial/interglacial cycles are therefore imprecise. We compare our refined climatic framework to a database of 64 radiometrically-dated paleoanthropological sites to test hypotheses of demographic response to climatic change among African hominin populations during the 150-30 ka interval. We argue that at a continental scale, population and climate changes were asynchronous and likely occurred under different regimes of climate forcing, creating alternating opportunities for migration into adjacent regions. Our results suggest little relation between large scale demographic and climate change in southern Africa during this time span, but strongly support the hypothesis of hominin occupation of the Sahara during discrete humid intervals ~135-115 ka and 105-75 ka. Hominin populations in equatorial and eastern Africa may have been buffered from the extremes of climate change by locally steep altitudinal and rainfall gradients and the complex and variable effects of increased aridity on human habitat suitability in the tropics. Our data are consistent with hominin migrations out of Africa through varying exit points from ~140-80 ka.
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http://dx.doi.org/10.1016/j.jhevol.2012.01.011DOI Listing
May 2012

The Pleistocene archaeology and environments of the Wasiriya Beds, Rusinga Island, Kenya.

J Hum Evol 2010 Dec 29;59(6):657-71. Epub 2010 Sep 29.

Center for the Study of Human Origins, Department of Anthropology, New York University, 25 Waverly Place, New York, NY 10012, USA.

Western Kenya is well known for abundant early Miocene hominoid fossils. However, the Wasiriya Beds of Rusinga Island, Kenya, preserve a Pleistocene sedimentary archive with radiocarbon age estimates of >33-45 ka that contains Middle Stone Age artifacts and abundant, well-preserved fossil fauna: a co-occurrence rare in eastern Africa, particularly in the region bounding Lake Victoria. Artifacts and fossils are associated with distal volcanic ash deposits that occur at multiple localities in the Wasiriya Beds, correlated on the basis of geochemical composition as determined by electron probe microanalysis. Sediment lithology and the fossil ungulates suggest a local fluvial system and associated riparian wooded habitat within a predominantly arid grassland setting that differs substantially from the modern environment, where local climate is strongly affected by moisture availability from Lake Victoria. In particular, the presence of oryx (Oryx gazella) and Grevy's zebra (Equus grevyi) suggest a pre-Last Glacial Maximum expansion of arid grasslands, an environmental reconstruction further supported by the presence of several extinct specialized grazers (Pelorovis antiquus, Megalotragus sp., and a small alcelaphine) that are unknown from Holocene deposits in eastern Africa. The combination of artifacts, a rich fossil fauna, and volcaniclastic sediments makes the Wasiriya Beds a key site for examining the Lake Victoria basin, a biogeographically important area for understanding the diversification and dispersal of Homo sapiens from Africa, whose pre-Last Glacial Maximum history remains poorly understood.
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http://dx.doi.org/10.1016/j.jhevol.2010.07.020DOI Listing
December 2010

The Middle Stone Age of the northern Kenyan Rift: age and context of new archaeological sites from the Kapedo Tuffs.

J Hum Evol 2008 Oct 30;55(4):652-64. Epub 2008 Jul 30.

Department of Anthropology, National Museum of Natural History, Smithsonian Institution, Washington DC, 20013-7012, USA.

Rift Valley sites in southern Ethiopia and northern Kenya preserve the oldest fossil remains attributed to Homo sapiens and the earliest archaeological sites attributed to the Middle Stone Age (MSA). New localities from the Kapedo Tuffs augment the sparse sample of MSA sites from the northern Kenya Rift. Tephrostratigraphic correlation with dated pyroclastic deposits from the adjacent volcano Silali suggests an age range of 135-123ka for archaeological sites of the Kapedo Tuffs. Comparisons of the Kapedo Tuffs archaeological assemblages with those from the adjacent Turkana and Baringo basins show broad lithic technological similarity but reveal that stone raw material availability is a key factor in explaining typologically defined archaeological variability within this region. Spatially and temporally resolved comparisons such as this provide the best means to link the biological and behavioral variation manifest in the record of early Homo sapiens.
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http://dx.doi.org/10.1016/j.jhevol.2008.03.008DOI Listing
October 2008

Tephrostratigraphy and the Acheulian to middle stone age transition in the Kapthurin Formation, Kenya.

J Hum Evol 2002 Jan-Feb;42(1-2):211-35

Department of Anthropology, University of Connecticut, Storrs, Connecticut 06269, USA.

Sites containing Acheulian, Sangoan, Fauresmith, and Middle Stone Age artefacts occur within and below the Bedded Tuff, a widespread volcaniclastic member of the Kapthurin Formation, Kenya. The Bedded Tuff eruptive complex consists of up to twelve tephra beds, intercalated sediments, and paleosols. Two pumiceous units, high in the Bedded Tuff sequence, have been dated by(40)Ar/(39)Ar, one to 235+/-2 ka (Deino & McBrearty, 2002, Journal of Human Evolution, 42, 185-210, cf. Tallon, 1978, Geological Background to Fossil Man, pp. 361-373, Scottish Academic Press), the other to 284+/-12 ka (Deino & McBrearty, 2001), the latter now providing a minimum age estimate for all underlying archaeological sites. Bedded Tuff outcrops are correlated through field stratigraphic and electron microprobe geochemical analyses of individual beds. Bedded Tuff units show increasingly evolved composition through the stratigraphic succession, indicating that the beds are the product of intermittent eruption of a single differentiating magma system, and the chemical signatures of these beds permit the chronological ordering of archaeological sites. Our results indicate that the transition to Middle Stone Age technology occurred prior to 285 ka in this region of East Africa. The interstratification of sites containing Acheulian, Sangoan, Fauresmith, and Middle Stone Age artefacts suggests that these technologies were contemporary in a single depositional basin over the duration of the transition.
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http://dx.doi.org/10.1006/jhev.2001.0513DOI Listing
March 2002