Colonisation of Sahul 70-60 thousand years ago (kya) represents the first great maritime migratio... more Colonisation of Sahul 70-60 thousand years ago (kya) represents the first great maritime migration undertaken by anatomically modern humans in one of the final phases of the Out of Africa dispersal. Visual connectivity network analyses, agent-based simulations and ocean current modelling reveal that modern humans could follow numerous northern and southern migration pathways into Sahul. Our results support a southern route out of Africa through South Asia with entry into ISEA through the Banda Arc, culminating in an early colonisation of Sahul on the northwest shelf. Our results show multiple colonisation events through other entry points were also probable, and raise interesting possibilities for complex regional migration and population histories.
Africa's southern Cape is a key region for the evolution of our species, with early symbolic syst... more Africa's southern Cape is a key region for the evolution of our species, with early symbolic systems, marine faunal exploitation, and episodic production of microlithic stone tools taken as evidence for the appearance of distinctively complex human behavior. However, the temporally discontinuous nature of this evidence precludes ready assumptions of intrinsic adaptive benefit, and has encouraged diverse explanations for the occurrence of these behaviors, in terms of regional demographic, social and ecological conditions. Here, we present a new high-resolution multi-proxy record of environmental change that indicates that faunal exploitation patterns and lithic technologies track climatic variation across the last 22,300 years in the southern Cape. Conditions during the Last Glacial Maximum and deglaciation were humid, and zooarchaeological data indicate high foraging returns. By contrast, the Holocene is characterized by much drier conditions and a degraded resource base. Critically, we demonstrate that systems for technological delivery e or provisioning e were responsive to changing humidity and environmental productivity. However, in contrast to prevailing models, bladelet-rich microlithic technologies were deployed under conditions of high foraging returns and abandoned in response to increased aridity and less productive subsistence environments. This suggests that posited links between microlithic technologies and subsistence risk are not universal, and the behavioral sophistication of human populations is reflected in their adaptive flexibility rather than in the use of specific technological systems.
Taphonomic analysis is an essential component of zooarchaeology, but is employed in different way... more Taphonomic analysis is an essential component of zooarchaeology, but is employed in different ways within different research traditions. Within the Africanist Palaeolithic literature, there is a strong emphasis on quantitative comparison of proportions of different bone surface modifications to one another and to proportions observed on modern experimental collections. This work has been driven by debates about the taphonomic histories of Oldowan sites that document the subsistence strategies of early Homo, but this specific approach can be usefully applied to a range of contexts across many different time periods and geographic locations. One obstacle to the cross-fertilization of this tapho-nomic tradition with other zooarchaeological work is the restrictive manner in which data are selected from an assemblage for analysis. To ensure comparability between fossil and modern assemblages, analysts typically exclude specimens with evidence for post-depositional modification not modeled in the experimental data. Although this adds interpretive robustness, it can diminish sample size significantly, sometimes to the point of affecting statistical analyses, and results in much time invested in collecting data that ultimately are not used. Here, we describe a new method for maximizing the number of specimens that can be incorporated into analysis, thus resolving the persistent problem of poor sample sizes to make more statistically robust comparisons to actualistic datasets.
The foraging behaviors of Middle Stone Age (MSA) early modern humans have largely been based on e... more 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 lumines-cence. 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.
Recent research from the site of Pella in Jordan examines the process and timing of olive cultiva... more Recent research from the site of Pella in Jordan examines the process and timing of olive cultivation. The frequent presence of olive remains from the Pottery Neolithic, beginning in the Yarmoukian, suggests that exploitation of the olive dates from as early as c. 6200 cal bce, with evidence of oil pressing from at least c. 5200 cal bce. Morphometric data, spanning the Late Neolithic to the Middle Iron Age II, using the measurement of olive endocarp length and width, demonstrates a reduction in the size variation of olive endocarps through time, in addition to an increase in their length, likely the result of selection pressure on trees. At Pella, this change occurs sometime after the Chalcolithic and before the Late Bronze Age, probably post-dating the earliest phases of the Early Bronze Age. Domestication is thus later than Teleilat Ghassul (Jordan), which has the earliest morphological evidence for olive domestication, and suggests that olive domestication was a regionally and temporally diverse process.
Zooarchaeologists frequently measure taxonomic evenness to document subsistence change and to und... more Zooarchaeologists frequently measure taxonomic evenness to document subsistence change and to understand the response of faunal communities to paleoenvironmental change. Although the measurement of evenness is commonplace , there are numerous challenges involved. Evenness indices are sensitive to changing richness, and by extension sample size, and various indices respond differently to changing taxonomic abundances (i.e., changing evenness). To refine protocol for comparing assemblages of varied sampling effort and identify indices that may be more useful for zooarchaeological applications, we examine the quantitative behavior of the widely used Shannon evenness and Simpson indices and two others more commonly used by ecologists. These indices are examined in relation to varied richness, sample size, and taxonomic abundances. We show that although zooarchaeologists are concerned with identifying and correcting for the effects of sample size on evenness, it may be appropriate to instead focus on how richness modulates evenness. Based on our analyses, we recommend the Simpson index for most zooarchaeological applications, except when comparing evenness across assemblages that are very even.
The East African Rift preserves the world's richest Middle and Late Pleistocene (~780e12 ... more The East African Rift preserves the world's richest Middle and Late Pleistocene (~780e12 ka) geological, archaeological and paleontological archives relevant to the emergence of Homo sapiens. This region also provides unparalleled chronological control for many important sites through tephrochronology, the dating and correlation of volcanic ashes as widespread isochronous markers in the geological record. There are many well-characterized Pliocene-Early Pleistocene tephras that are widespread across East Africa. A comparable framework is lacking for the Middle and Late Pleistocene; a period characterized by spatially and temporally complex patterns of climate change, as well as the emergence of modern Homo sapiens and the dispersal of this species across and out of Africa. Unraveling relationships among these spatial and temporally complex phenomena requires a precise chronology. To this end we report the Menengai Tuff, a widespread volcanic ash produced by the large-scale caldera-forming eruption in Kenya and 40 Ar/ 39 Ar dated to 35.62 ± 0.26 ka. Geochemical characterization of 565 glass shards from 36 samples by wavelength-dispersive electron probe microanalysis show the Menengai Tuff was deposited over >115,000 km 2 and is found in the Baringo, Chalbi, Elmenteita, Nakuru, Olorgesailie, Turkana, and Victoria basins, all of which preserve rich Late Pleistocene paleoenvironmental and archaeological archives. Correlation and dating of the Menengai Tuff demonstrate that it is the most widespread tephra and largest eruption currently known from the Late Pleistocene of East Africa. As such, it is a valuable marker in establishing a Late Pleistocene chronology for paleoclimatic, archeological, and paleontological records relevant to the study of human evolution.
The East African Rift preserves the world's richest Middle and Late Pleistocene (~780e12 ka) geol... more The East African Rift preserves the world's richest Middle and Late Pleistocene (~780e12 ka) geological, archaeological and paleontological archives relevant to the emergence of Homo sapiens. This region also provides unparalleled chronological control for many important sites through tephrochronology, the dating and correlation of volcanic ashes as widespread isochronous markers in the geological record. There are many well-characterized Pliocene-Early Pleistocene tephras that are widespread across East Africa. A comparable framework is lacking for the Middle and Late Pleistocene; a period characterized by spatially and temporally complex patterns of climate change, as well as the emergence of modern Homo sapiens and the dispersal of this species across and out of Africa. Unraveling relationships among these spatial and temporally complex phenomena requires a precise chronology. To this end we report the Menengai Tuff, a widespread volcanic ash produced by the large-scale caldera-forming eruption in Kenya and 40 Ar/ 39 Ar dated to 35.62 ± 0.26 ka. Geochemical characterization of 565 glass shards from 36 samples by wavelength-dispersive electron probe microanalysis show the Menengai Tuff was deposited over >115,000 km 2 and is found in the Baringo, Chalbi, Elmenteita, Nakuru, Olorgesailie, Turkana, and Victoria basins, all of which preserve rich Late Pleistocene paleoenvironmental and archaeological archives. Correlation and dating of the Menengai Tuff demonstrate that it is the most widespread tephra and largest eruption currently known from the Late Pleistocene of East Africa. As such, it is a valuable marker in establishing a Late Pleistocene chronology for paleoclimatic, archeological, and paleontological records relevant to the study of human evolution.
Pleistocene palaeoclimates and palaeoenvironments of southernmost Africa are important for unders... more Pleistocene palaeoclimates and palaeoenvironments of southernmost Africa are important for understanding southern hemisphere climate dynamics and for reconstructing human evolution and early human settlement in this region. Measurements of d 13 C in tooth enamel of 136 faunal specimens from the archaeological site of Boomplaas Cave, South Africa, show significant shifts in proportions of C 3 and C 4 vegetation from the earliest deposits, probably dating to Marine Isotope Stage (MIS) 5, to the late Holocene. Vegetation communities during the Last Glacial Maximum were strongly C 3-dominated, indicating an eastward expansion of the winter rainfall zone at this time. This is consistent with climate models postulating northwards shift and/or intensification of the circumpolar westerly frontal systems during glacials. Winter rainfall and lower temperatures, both of which favour C 3 grasses, were clearly more important than lower pCO 2 (which favours C 4 grasses) in determining the nature of the vegetation. The intervals 40–36 and 17–14k cal a BP supported substantial quantities of C 4 grasses, indicating a greater proportion of summer rainfall at these times. These two intervals correspond with warmer climates as reflected in Antarctic ice cores. d 13 C of an as yet unnamed caprine indicate that these animals were primarily C 3 grazers.
The East African Rift preserves the world's richest Middle and Late Pleistocene (~780e12 ka) geol... more The East African Rift preserves the world's richest Middle and Late Pleistocene (~780e12 ka) geological, archaeological and paleontological archives relevant to the emergence of Homo sapiens. This region also provides unparalleled chronological control for many important sites through tephrochronology, the dating and correlation of volcanic ashes as widespread isochronous markers in the geological record. There are many well-characterized Pliocene-Early Pleistocene tephras that are widespread across East Africa. A comparable framework is lacking for the Middle and Late Pleistocene; a period characterized by spatially and temporally complex patterns of climate change, as well as the emergence of modern Homo sapiens and the dispersal of this species across and out of Africa. Unraveling relationships among these spatial and temporally complex phenomena requires a precise chronology. To this end we report the Menengai Tuff, a widespread volcanic ash produced by the large-scale caldera-forming eruption in Kenya and 40 Ar/ 39 Ar dated to 35.62 ± 0.26 ka. Geochemical characterization of 565 glass shards from 36 samples by wavelength-dispersive electron probe microanalysis show the Menengai Tuff was deposited over >115,000 km 2 and is found in the Baringo, Chalbi, Elmenteita, Nakuru, Olorgesailie, Turkana, and Victoria basins, all of which preserve rich Late Pleistocene paleoenvironmental and archaeological archives. Correlation and dating of the Menengai Tuff demonstrate that it is the most widespread tephra and largest eruption currently known from the Late Pleistocene of East Africa. As such, it is a valuable marker in establishing a Late Pleistocene chronology for paleoclimatic, archeological, and paleontological records relevant to the study of human evolution.
The precipitation history of south-west Australia since the Last Glacial Maximum (LGM) has
import... more The precipitation history of south-west Australia since the Last Glacial Maximum (LGM) has important implications for understanding southern hemisphere climate dynamics. Previously reported environmental records indicating more open vegetation during the LGM have been interpreted in terms of aridity, but such changes can be explained by alternative mechanisms. To provide new evidence concerning the region’s Quaternary precipitation history, we examine temporal changes in large mammal richness at four south-west Australian fossil sites: Devil’s Lair, Tunnel Cave, Witchcliffe Rock Shelter and Rainbow Cave. Large mammal richness is correlated strongly with mean annual precipitation across 53 modern Australian communities. Extending this relationship to the fossil record, a steady increase in richness from the LGM to the onset of the Holocene at both Devil’s Lair and Tunnel Cave is consistent with increased precipitation through time. This supports previous interpretations of a more arid LGM and implies regional heterogeneity in the position of the southern hemisphere westerlies. A reduction in richness during the last 1000 years is unlikely to be the result of precipitation change and may be related to more frequent burning of the landscape by hunter-gatherers in an effort to increase availability of large prey.
The precipitation history of southwest Australia since the Last Glacial Maximum (LGM) has importa... more The precipitation history of southwest Australia since the Last Glacial Maximum (LGM) has important implications for understanding southern hemisphere climate dynamics. Previously reported environmental records indicating more open vegetation during the LGM have been interpreted in terms of aridity, but such changes can be explained by alternative mechanisms. To provide new evidence concerning the region's Quaternary precipitation history, we examine temporal changes in large mammal richness at four southwest Australian fossil sites: Devil's Lair, Tunnel Cave, Witchcliffe Rock Shelter and Rainbow Cave. Large mammal richness is correlated strongly with mean annual precipitation across 53 modern Australian communities. Extending this relationship to the fossil record, a steady increase in richness from the LGM to the onset of the Holocene at both Devil's Lair and Tunnel Cave is consistent with increased precipitation through time. This supports previous interpretations of a more arid LGM and implies regional heterogeneity in the position of the southern hemisphere westerlies. A reduction in richness during the last 1000 years is unlikely to be the result of precipitation change and may be related to more frequent burning of the landscape by hunter-gatherers in an effort to increase availability of large prey.
Understanding how ecological communities are organized and how they change through time is critic... more Understanding how ecological communities are organized and how they change through time is critical to predicting the effects of climate change 1. Recent work documenting the co-occurrence structure of modern communities found that most significant species pairs co-occur less frequently than would be expected by chance 2,3. However, little is known about how co-occurrence structure changes through time. Here we evaluate changes in plant and animal community organization over geological time by quantifying the co-occurrence structure of 359,896 unique taxon pairs in 80 assemblages spanning the past 300 million years. Co-occurrences of most taxon pairs were statistically random, but a significant fraction were spatially aggregated or segregated. Aggregated pairs dominated from the Carboniferous period (307 million years ago) to the early Holocene epoch (11,700 years before present), when there was a pronounced shift to more segregated pairs, a trend that continues in modern assemblages. The shift began during the Holocene and coincided with increasing human population size 4,5 and the spread of agriculture in North America 6,7. Before the shift, an average of 64% of significant pairs were aggregated; after the shift, the average dropped to 37%. The organization of modern and late Holocene plant and animal assemblages differs fundamentally from that of assemblages over the past 300 million years that predate the large-scale impacts of humans. Our results suggest that the rules governing the assembly of communities have recently been changed by human activity.
Increased population density is among the proposed drivers of the behaviour-al changes culminatin... more Increased population density is among the proposed drivers of the behaviour-al 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'.
The terminal Pleistocene is a period of profound climatic and environmental change in Africa, wit... more The terminal Pleistocene is a period of profound climatic and environmental change in Africa, with paleoenvironmental records documenting tremendous regional variation. Environmental records needed to understand these dynamics are currently lacking from the Horn of Africa. Here we provide a new paleoenvironmental record based of new faunal data from archeological sites along the Bulbula River (Ziway–Shala Basin, Main Ethiopian Rift) in Ethiopia. Research conducted in this area has uncovered archeological assemblages that document various phases of the Late Pleistocene and Early Holocene. Two sites dated to the terminal Pleistocene are considered here, B1s1 and B1s4. The former includes a very large assemblage of more than 20,000 skeletal remains. Both faunal assemblages are dominated by bovids of the tribes Alcelaphini and Antilopini and include Damaliscus hypsodon, a small extinct alcelaphine. The faunal remains from these sites, like those from the contemporary site of Lukenya Hill in south-central Kenya, are indicative of widespread arid grasslands. Several ungulates are found outside of their historic ranges, including Grant's gazelle (Nanger granti) and Dorcas gazelle (Gazella dorcas). Their absence from the region today likely reflects a combination of paleoenvironmental change since the end of the Pleistocene coupled with more recent human impacts. The combination of archeological and faunal data suggests that B1s1 could have been a residential site with seasonal occupation to acquire raw material from local obsidian sources and to hunt bovids in the arid plain, including species that ultimately disappear or shift their range at the onset of the Holocene with the return of warmer and moister conditions.
This study develops a new proxy for Quaternary temperature change in tropical Africa through anal... more This study develops a new proxy for Quaternary temperature change in tropical Africa through analysis of size variation in East African mole-rat (Tachyoryctes splendens). In modern mole-rats, mandibular alveolar length is unrelated to annual precipitation, precipitation seasonality, temperature seasonality, or primary productivity. However, it is inversely correlated with mean annual temperature, in agreement with Bergmann's rule. This relationship is observed at temperatures below ~17.3 C, but not at higher temperatures. We apply these observations to late Quaternary mole-rats from Wakondo (~100 ka) and Kisaaka (~50 ka) in the Lake Victoria region and Enkapune ya Muto (EYM; ~7.2e3.2 ka) in Kenya's central rift. The Lake Victoria mole-rats are larger than expected for populations from warm climates typical of the area today, implying cooler temperatures in the past. The magnitude of temperature decline needed to drive the size shift is substantial (~4e6 C), similar in magnitude to the degree of change between the Last Glacial Maximum and Holocene, but is consistent with regional temperature records and with scenarios linking equatorial African temperature to northern hemisphere summer insolation. Size changes through time at EYM indicate that rising temperatures during the middle Holocene accompanied and potentially contributed to a decline in Lake Naivasha and expansion of grassland vegetation.
Colonisation of Sahul 70-60 thousand years ago (kya) represents the first great maritime migratio... more Colonisation of Sahul 70-60 thousand years ago (kya) represents the first great maritime migration undertaken by anatomically modern humans in one of the final phases of the Out of Africa dispersal. Visual connectivity network analyses, agent-based simulations and ocean current modelling reveal that modern humans could follow numerous northern and southern migration pathways into Sahul. Our results support a southern route out of Africa through South Asia with entry into ISEA through the Banda Arc, culminating in an early colonisation of Sahul on the northwest shelf. Our results show multiple colonisation events through other entry points were also probable, and raise interesting possibilities for complex regional migration and population histories.
Africa's southern Cape is a key region for the evolution of our species, with early symbolic syst... more Africa's southern Cape is a key region for the evolution of our species, with early symbolic systems, marine faunal exploitation, and episodic production of microlithic stone tools taken as evidence for the appearance of distinctively complex human behavior. However, the temporally discontinuous nature of this evidence precludes ready assumptions of intrinsic adaptive benefit, and has encouraged diverse explanations for the occurrence of these behaviors, in terms of regional demographic, social and ecological conditions. Here, we present a new high-resolution multi-proxy record of environmental change that indicates that faunal exploitation patterns and lithic technologies track climatic variation across the last 22,300 years in the southern Cape. Conditions during the Last Glacial Maximum and deglaciation were humid, and zooarchaeological data indicate high foraging returns. By contrast, the Holocene is characterized by much drier conditions and a degraded resource base. Critically, we demonstrate that systems for technological delivery e or provisioning e were responsive to changing humidity and environmental productivity. However, in contrast to prevailing models, bladelet-rich microlithic technologies were deployed under conditions of high foraging returns and abandoned in response to increased aridity and less productive subsistence environments. This suggests that posited links between microlithic technologies and subsistence risk are not universal, and the behavioral sophistication of human populations is reflected in their adaptive flexibility rather than in the use of specific technological systems.
Taphonomic analysis is an essential component of zooarchaeology, but is employed in different way... more Taphonomic analysis is an essential component of zooarchaeology, but is employed in different ways within different research traditions. Within the Africanist Palaeolithic literature, there is a strong emphasis on quantitative comparison of proportions of different bone surface modifications to one another and to proportions observed on modern experimental collections. This work has been driven by debates about the taphonomic histories of Oldowan sites that document the subsistence strategies of early Homo, but this specific approach can be usefully applied to a range of contexts across many different time periods and geographic locations. One obstacle to the cross-fertilization of this tapho-nomic tradition with other zooarchaeological work is the restrictive manner in which data are selected from an assemblage for analysis. To ensure comparability between fossil and modern assemblages, analysts typically exclude specimens with evidence for post-depositional modification not modeled in the experimental data. Although this adds interpretive robustness, it can diminish sample size significantly, sometimes to the point of affecting statistical analyses, and results in much time invested in collecting data that ultimately are not used. Here, we describe a new method for maximizing the number of specimens that can be incorporated into analysis, thus resolving the persistent problem of poor sample sizes to make more statistically robust comparisons to actualistic datasets.
The foraging behaviors of Middle Stone Age (MSA) early modern humans have largely been based on e... more 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 lumines-cence. 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.
Recent research from the site of Pella in Jordan examines the process and timing of olive cultiva... more Recent research from the site of Pella in Jordan examines the process and timing of olive cultivation. The frequent presence of olive remains from the Pottery Neolithic, beginning in the Yarmoukian, suggests that exploitation of the olive dates from as early as c. 6200 cal bce, with evidence of oil pressing from at least c. 5200 cal bce. Morphometric data, spanning the Late Neolithic to the Middle Iron Age II, using the measurement of olive endocarp length and width, demonstrates a reduction in the size variation of olive endocarps through time, in addition to an increase in their length, likely the result of selection pressure on trees. At Pella, this change occurs sometime after the Chalcolithic and before the Late Bronze Age, probably post-dating the earliest phases of the Early Bronze Age. Domestication is thus later than Teleilat Ghassul (Jordan), which has the earliest morphological evidence for olive domestication, and suggests that olive domestication was a regionally and temporally diverse process.
Zooarchaeologists frequently measure taxonomic evenness to document subsistence change and to und... more Zooarchaeologists frequently measure taxonomic evenness to document subsistence change and to understand the response of faunal communities to paleoenvironmental change. Although the measurement of evenness is commonplace , there are numerous challenges involved. Evenness indices are sensitive to changing richness, and by extension sample size, and various indices respond differently to changing taxonomic abundances (i.e., changing evenness). To refine protocol for comparing assemblages of varied sampling effort and identify indices that may be more useful for zooarchaeological applications, we examine the quantitative behavior of the widely used Shannon evenness and Simpson indices and two others more commonly used by ecologists. These indices are examined in relation to varied richness, sample size, and taxonomic abundances. We show that although zooarchaeologists are concerned with identifying and correcting for the effects of sample size on evenness, it may be appropriate to instead focus on how richness modulates evenness. Based on our analyses, we recommend the Simpson index for most zooarchaeological applications, except when comparing evenness across assemblages that are very even.
The East African Rift preserves the world's richest Middle and Late Pleistocene (~780e12 ... more The East African Rift preserves the world's richest Middle and Late Pleistocene (~780e12 ka) geological, archaeological and paleontological archives relevant to the emergence of Homo sapiens. This region also provides unparalleled chronological control for many important sites through tephrochronology, the dating and correlation of volcanic ashes as widespread isochronous markers in the geological record. There are many well-characterized Pliocene-Early Pleistocene tephras that are widespread across East Africa. A comparable framework is lacking for the Middle and Late Pleistocene; a period characterized by spatially and temporally complex patterns of climate change, as well as the emergence of modern Homo sapiens and the dispersal of this species across and out of Africa. Unraveling relationships among these spatial and temporally complex phenomena requires a precise chronology. To this end we report the Menengai Tuff, a widespread volcanic ash produced by the large-scale caldera-forming eruption in Kenya and 40 Ar/ 39 Ar dated to 35.62 ± 0.26 ka. Geochemical characterization of 565 glass shards from 36 samples by wavelength-dispersive electron probe microanalysis show the Menengai Tuff was deposited over >115,000 km 2 and is found in the Baringo, Chalbi, Elmenteita, Nakuru, Olorgesailie, Turkana, and Victoria basins, all of which preserve rich Late Pleistocene paleoenvironmental and archaeological archives. Correlation and dating of the Menengai Tuff demonstrate that it is the most widespread tephra and largest eruption currently known from the Late Pleistocene of East Africa. As such, it is a valuable marker in establishing a Late Pleistocene chronology for paleoclimatic, archeological, and paleontological records relevant to the study of human evolution.
The East African Rift preserves the world's richest Middle and Late Pleistocene (~780e12 ka) geol... more The East African Rift preserves the world's richest Middle and Late Pleistocene (~780e12 ka) geological, archaeological and paleontological archives relevant to the emergence of Homo sapiens. This region also provides unparalleled chronological control for many important sites through tephrochronology, the dating and correlation of volcanic ashes as widespread isochronous markers in the geological record. There are many well-characterized Pliocene-Early Pleistocene tephras that are widespread across East Africa. A comparable framework is lacking for the Middle and Late Pleistocene; a period characterized by spatially and temporally complex patterns of climate change, as well as the emergence of modern Homo sapiens and the dispersal of this species across and out of Africa. Unraveling relationships among these spatial and temporally complex phenomena requires a precise chronology. To this end we report the Menengai Tuff, a widespread volcanic ash produced by the large-scale caldera-forming eruption in Kenya and 40 Ar/ 39 Ar dated to 35.62 ± 0.26 ka. Geochemical characterization of 565 glass shards from 36 samples by wavelength-dispersive electron probe microanalysis show the Menengai Tuff was deposited over >115,000 km 2 and is found in the Baringo, Chalbi, Elmenteita, Nakuru, Olorgesailie, Turkana, and Victoria basins, all of which preserve rich Late Pleistocene paleoenvironmental and archaeological archives. Correlation and dating of the Menengai Tuff demonstrate that it is the most widespread tephra and largest eruption currently known from the Late Pleistocene of East Africa. As such, it is a valuable marker in establishing a Late Pleistocene chronology for paleoclimatic, archeological, and paleontological records relevant to the study of human evolution.
Pleistocene palaeoclimates and palaeoenvironments of southernmost Africa are important for unders... more Pleistocene palaeoclimates and palaeoenvironments of southernmost Africa are important for understanding southern hemisphere climate dynamics and for reconstructing human evolution and early human settlement in this region. Measurements of d 13 C in tooth enamel of 136 faunal specimens from the archaeological site of Boomplaas Cave, South Africa, show significant shifts in proportions of C 3 and C 4 vegetation from the earliest deposits, probably dating to Marine Isotope Stage (MIS) 5, to the late Holocene. Vegetation communities during the Last Glacial Maximum were strongly C 3-dominated, indicating an eastward expansion of the winter rainfall zone at this time. This is consistent with climate models postulating northwards shift and/or intensification of the circumpolar westerly frontal systems during glacials. Winter rainfall and lower temperatures, both of which favour C 3 grasses, were clearly more important than lower pCO 2 (which favours C 4 grasses) in determining the nature of the vegetation. The intervals 40–36 and 17–14k cal a BP supported substantial quantities of C 4 grasses, indicating a greater proportion of summer rainfall at these times. These two intervals correspond with warmer climates as reflected in Antarctic ice cores. d 13 C of an as yet unnamed caprine indicate that these animals were primarily C 3 grazers.
The East African Rift preserves the world's richest Middle and Late Pleistocene (~780e12 ka) geol... more The East African Rift preserves the world's richest Middle and Late Pleistocene (~780e12 ka) geological, archaeological and paleontological archives relevant to the emergence of Homo sapiens. This region also provides unparalleled chronological control for many important sites through tephrochronology, the dating and correlation of volcanic ashes as widespread isochronous markers in the geological record. There are many well-characterized Pliocene-Early Pleistocene tephras that are widespread across East Africa. A comparable framework is lacking for the Middle and Late Pleistocene; a period characterized by spatially and temporally complex patterns of climate change, as well as the emergence of modern Homo sapiens and the dispersal of this species across and out of Africa. Unraveling relationships among these spatial and temporally complex phenomena requires a precise chronology. To this end we report the Menengai Tuff, a widespread volcanic ash produced by the large-scale caldera-forming eruption in Kenya and 40 Ar/ 39 Ar dated to 35.62 ± 0.26 ka. Geochemical characterization of 565 glass shards from 36 samples by wavelength-dispersive electron probe microanalysis show the Menengai Tuff was deposited over >115,000 km 2 and is found in the Baringo, Chalbi, Elmenteita, Nakuru, Olorgesailie, Turkana, and Victoria basins, all of which preserve rich Late Pleistocene paleoenvironmental and archaeological archives. Correlation and dating of the Menengai Tuff demonstrate that it is the most widespread tephra and largest eruption currently known from the Late Pleistocene of East Africa. As such, it is a valuable marker in establishing a Late Pleistocene chronology for paleoclimatic, archeological, and paleontological records relevant to the study of human evolution.
The precipitation history of south-west Australia since the Last Glacial Maximum (LGM) has
import... more The precipitation history of south-west Australia since the Last Glacial Maximum (LGM) has important implications for understanding southern hemisphere climate dynamics. Previously reported environmental records indicating more open vegetation during the LGM have been interpreted in terms of aridity, but such changes can be explained by alternative mechanisms. To provide new evidence concerning the region’s Quaternary precipitation history, we examine temporal changes in large mammal richness at four south-west Australian fossil sites: Devil’s Lair, Tunnel Cave, Witchcliffe Rock Shelter and Rainbow Cave. Large mammal richness is correlated strongly with mean annual precipitation across 53 modern Australian communities. Extending this relationship to the fossil record, a steady increase in richness from the LGM to the onset of the Holocene at both Devil’s Lair and Tunnel Cave is consistent with increased precipitation through time. This supports previous interpretations of a more arid LGM and implies regional heterogeneity in the position of the southern hemisphere westerlies. A reduction in richness during the last 1000 years is unlikely to be the result of precipitation change and may be related to more frequent burning of the landscape by hunter-gatherers in an effort to increase availability of large prey.
The precipitation history of southwest Australia since the Last Glacial Maximum (LGM) has importa... more The precipitation history of southwest Australia since the Last Glacial Maximum (LGM) has important implications for understanding southern hemisphere climate dynamics. Previously reported environmental records indicating more open vegetation during the LGM have been interpreted in terms of aridity, but such changes can be explained by alternative mechanisms. To provide new evidence concerning the region's Quaternary precipitation history, we examine temporal changes in large mammal richness at four southwest Australian fossil sites: Devil's Lair, Tunnel Cave, Witchcliffe Rock Shelter and Rainbow Cave. Large mammal richness is correlated strongly with mean annual precipitation across 53 modern Australian communities. Extending this relationship to the fossil record, a steady increase in richness from the LGM to the onset of the Holocene at both Devil's Lair and Tunnel Cave is consistent with increased precipitation through time. This supports previous interpretations of a more arid LGM and implies regional heterogeneity in the position of the southern hemisphere westerlies. A reduction in richness during the last 1000 years is unlikely to be the result of precipitation change and may be related to more frequent burning of the landscape by hunter-gatherers in an effort to increase availability of large prey.
Understanding how ecological communities are organized and how they change through time is critic... more Understanding how ecological communities are organized and how they change through time is critical to predicting the effects of climate change 1. Recent work documenting the co-occurrence structure of modern communities found that most significant species pairs co-occur less frequently than would be expected by chance 2,3. However, little is known about how co-occurrence structure changes through time. Here we evaluate changes in plant and animal community organization over geological time by quantifying the co-occurrence structure of 359,896 unique taxon pairs in 80 assemblages spanning the past 300 million years. Co-occurrences of most taxon pairs were statistically random, but a significant fraction were spatially aggregated or segregated. Aggregated pairs dominated from the Carboniferous period (307 million years ago) to the early Holocene epoch (11,700 years before present), when there was a pronounced shift to more segregated pairs, a trend that continues in modern assemblages. The shift began during the Holocene and coincided with increasing human population size 4,5 and the spread of agriculture in North America 6,7. Before the shift, an average of 64% of significant pairs were aggregated; after the shift, the average dropped to 37%. The organization of modern and late Holocene plant and animal assemblages differs fundamentally from that of assemblages over the past 300 million years that predate the large-scale impacts of humans. Our results suggest that the rules governing the assembly of communities have recently been changed by human activity.
Increased population density is among the proposed drivers of the behaviour-al changes culminatin... more Increased population density is among the proposed drivers of the behaviour-al 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'.
The terminal Pleistocene is a period of profound climatic and environmental change in Africa, wit... more The terminal Pleistocene is a period of profound climatic and environmental change in Africa, with paleoenvironmental records documenting tremendous regional variation. Environmental records needed to understand these dynamics are currently lacking from the Horn of Africa. Here we provide a new paleoenvironmental record based of new faunal data from archeological sites along the Bulbula River (Ziway–Shala Basin, Main Ethiopian Rift) in Ethiopia. Research conducted in this area has uncovered archeological assemblages that document various phases of the Late Pleistocene and Early Holocene. Two sites dated to the terminal Pleistocene are considered here, B1s1 and B1s4. The former includes a very large assemblage of more than 20,000 skeletal remains. Both faunal assemblages are dominated by bovids of the tribes Alcelaphini and Antilopini and include Damaliscus hypsodon, a small extinct alcelaphine. The faunal remains from these sites, like those from the contemporary site of Lukenya Hill in south-central Kenya, are indicative of widespread arid grasslands. Several ungulates are found outside of their historic ranges, including Grant's gazelle (Nanger granti) and Dorcas gazelle (Gazella dorcas). Their absence from the region today likely reflects a combination of paleoenvironmental change since the end of the Pleistocene coupled with more recent human impacts. The combination of archeological and faunal data suggests that B1s1 could have been a residential site with seasonal occupation to acquire raw material from local obsidian sources and to hunt bovids in the arid plain, including species that ultimately disappear or shift their range at the onset of the Holocene with the return of warmer and moister conditions.
This study develops a new proxy for Quaternary temperature change in tropical Africa through anal... more This study develops a new proxy for Quaternary temperature change in tropical Africa through analysis of size variation in East African mole-rat (Tachyoryctes splendens). In modern mole-rats, mandibular alveolar length is unrelated to annual precipitation, precipitation seasonality, temperature seasonality, or primary productivity. However, it is inversely correlated with mean annual temperature, in agreement with Bergmann's rule. This relationship is observed at temperatures below ~17.3 C, but not at higher temperatures. We apply these observations to late Quaternary mole-rats from Wakondo (~100 ka) and Kisaaka (~50 ka) in the Lake Victoria region and Enkapune ya Muto (EYM; ~7.2e3.2 ka) in Kenya's central rift. The Lake Victoria mole-rats are larger than expected for populations from warm climates typical of the area today, implying cooler temperatures in the past. The magnitude of temperature decline needed to drive the size shift is substantial (~4e6 C), similar in magnitude to the degree of change between the Last Glacial Maximum and Holocene, but is consistent with regional temperature records and with scenarios linking equatorial African temperature to northern hemisphere summer insolation. Size changes through time at EYM indicate that rising temperatures during the middle Holocene accompanied and potentially contributed to a decline in Lake Naivasha and expansion of grassland vegetation.
Polynesian adze sourcing studies that rely on geochemical analyses to assign distant artefacts to... more Polynesian adze sourcing studies that rely on geochemical analyses to assign distant artefacts to a source or quarry have been undertaken for more than three decades. Understanding intra-source geochemical variability is essential for robust artefact source assignments, yet these data are not available for most quarries. We provide a seven-step protocol for sampling source rocks and associated artefacts at quarries and, using the large Eiao quarry (Marquesas Islands) as a case study, demonstrate the efficacy of the protocol. A “sampling to redundancy” statistical procedure documents that ~7–11 samples are required to capture the variability of 10 oxides, 49 trace elements and seven isotope ratios. We advocate using the broadest array of fully quantitative geochemical values to characterise quarries and sources that will facilitate current and future sourcing studies. In the biological sense, this is analogous to the formal description of a holotype. Quarry samples should also be collected and curated to enable research when new protocols are established and more precise and accurate geochemical techniques develop.
Dating late Quaternary terrestrial strata is especially challenging beyond the ~50 ka limit of 14... more Dating late Quaternary terrestrial strata is especially challenging beyond the ~50 ka limit of 14C. Ostrich eggshell fragments (OES) are common in African archaeological sequences, consist of ~2 mm-thick low-Mg calcite with 1-3% organics, and are resistant to diagenesis in semi-arid to arid soils over geologic timescales. OES are amenable to 14C dating and are geochemically suitable for U-Th dating, though previous attempts neglected to account for secondary U derived from soil water upon burial. Recent work has shown that U-Th “burial dates” on OES are concordant with 14C dates for ~10-50 ka OES from an African rockshelter. We present LA-ICP-MS profiles of U and 232Th for ancient OES from 8 archaeological sites in sub-Saharan Africa spanning ~10 to >500 ka. They reveal undesirable elevated detrital 232Th and erratic 238U near OES surfaces and in secondary calcite filling macroscopic pores, guiding optimal sampling for dating. Patterns of U and 232Th are similar in OES from all localities and do not vary systematically with age, suggesting U uptake is self-limiting and [U] is controlled by soil composition. All OES have steep smooth gradients of [238U] (~100s to 10s of ppb) starting at or near their outer surface, continuing through the “palisade layer”, then dropping to near zero (primary) values, consistent with diffusive U uptake. SEM imaging and erfc-1(U/U0) v. distance plots indicate OES calcite structures control U diffusivity. OES >500 ka retain coherent U profiles, suggesting that U-Th burial dating of OES may be useful to the limit of secular equilibrium.
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important implications for understanding southern hemisphere climate dynamics. Previously reported environmental
records indicating more open vegetation during the LGM have been interpreted in terms of aridity, but such
changes can be explained by alternative mechanisms. To provide new evidence concerning the region’s
Quaternary precipitation history, we examine temporal changes in large mammal richness at four south-west
Australian fossil sites: Devil’s Lair, Tunnel Cave, Witchcliffe Rock Shelter and Rainbow Cave. Large mammal
richness is correlated strongly with mean annual precipitation across 53 modern Australian communities. Extending
this relationship to the fossil record, a steady increase in richness from the LGM to the onset of the Holocene at
both Devil’s Lair and Tunnel Cave is consistent with increased precipitation through time. This supports previous
interpretations of a more arid LGM and implies regional heterogeneity in the position of the southern hemisphere
westerlies. A reduction in richness during the last 1000 years is unlikely to be the result of precipitation change
and may be related to more frequent burning of the landscape by hunter-gatherers in an effort to increase
availability of large prey.
important implications for understanding southern hemisphere climate dynamics. Previously reported environmental
records indicating more open vegetation during the LGM have been interpreted in terms of aridity, but such
changes can be explained by alternative mechanisms. To provide new evidence concerning the region’s
Quaternary precipitation history, we examine temporal changes in large mammal richness at four south-west
Australian fossil sites: Devil’s Lair, Tunnel Cave, Witchcliffe Rock Shelter and Rainbow Cave. Large mammal
richness is correlated strongly with mean annual precipitation across 53 modern Australian communities. Extending
this relationship to the fossil record, a steady increase in richness from the LGM to the onset of the Holocene at
both Devil’s Lair and Tunnel Cave is consistent with increased precipitation through time. This supports previous
interpretations of a more arid LGM and implies regional heterogeneity in the position of the southern hemisphere
westerlies. A reduction in richness during the last 1000 years is unlikely to be the result of precipitation change
and may be related to more frequent burning of the landscape by hunter-gatherers in an effort to increase
availability of large prey.