Proceedings of the National Academy of Sciences, 2021
Significance Understanding the evolution, dispersals, behaviors, and ecologies of early African H... more Significance Understanding the evolution, dispersals, behaviors, and ecologies of early African Homo sapiens requires accurate geochronological placement of fossils and artifacts. We introduce open-air occurrences of such remains in sediments of the Middle Awash study area in Ethiopia. We describe the stratigraphic and depositional contexts of our discoveries and demonstrate the effectiveness of recently developed uranium-series dating of ostrich eggshell at validating and bridging across more traditional radioisotopic methods ( 14 C and 40 Ar/ 39 Ar). Homo sapiens fossils and associated Middle Stone Age artifacts are placed at >158 and ∼96 ka. Later Stone Age occurrences are dated to ∼21 to 24 ka and ∼31 to 32 ka, firmly dating the upper portion of one of the longest records of human evolution.
This book presents a beautiful photo collection of the Konso stone tools, the Acheulean artifacts... more This book presents a beautiful photo collection of the Konso stone tools, the Acheulean artifacts. These artifacts include the world's oldest stone tools shaped to preconceived form. The volume illustrates early stone tool technology and its development from 1.75 to fewer than 1 million years ago.
The Hippopotamidae have been a major component of the African wetland fauna for the last 7 millio... more The Hippopotamidae have been a major component of the African wetland fauna for the last 7 million years, following the 'Hippopotamine Event,' i.e., the sudden emergence in the fossil record of the subfamily Hippopotaminae, including both extant species. The general dearth of African fossiliferous deposits dated between 9.5 Ma and 7.5 Ma concealed until now the evolution that led to the Hippopotamine Event and the subsequent success of these large semiaquatic herbivores. Part of this evolution is unveiled by the hippopotamid dental remains found at Chorora, a late Miocene site of the southern Afar Depression in Ethiopia spanning most of the fossil-depleted time interval. Although fragmentary, these remains represent a new, mid-sized hippopotamid species dated to ca. 8 Ma, as well as a somewhat younger, larger form. A cladistic analysis of a large array of cetartiodactyls indicates that the Chorora taxa were basal to the latest Miocene hippopotamines. The new species displays a mosaic of dental characters that support the attribution of the new species to a new genus within Hippopotaminae. The new fossils also clarify the course of early hippopotamine dental evolution. The Chorora hippopotamids suggest that transition to a marked abundance of hippopotamines with their unique dental pattern in African ecosystems occurred within a relatively short time interval, most probably between 8 Ma and 7.5 Ma. http://zoobank.org/urn:lsid:zoobank.org:pub:47B9381F-E3B5-40C9-B9AB-51CC3D0D3A8A
Proceedings of the National Academy of Sciences, 2020
Significance We report a rare example of a 1.4-million-y-old large bone fragment shaped into hand... more Significance We report a rare example of a 1.4-million-y-old large bone fragment shaped into handaxe-like form. This bone tool derives from the Konso Formation in southern Ethiopia, where abundant early Acheulean stone artifacts show considerable technological progression between ∼1.75 and <1.0 Mya. Technological analysis of the bone tool indicates intensive anthropogenic shaping. Edge damage, polish, and striae patterns are consistent with use in longitudinal motions, such as in butchering. The discovery of this bone handaxe shows that advanced flaking technology, practiced at Konso on a variety of lithic materials, was also applied to bone, thus expanding the known technological repertoire of African Early Pleistocene Homo .
Six Milllon Years of Volcanic, Tectonic,Paleoenvironmental, and Paleoanthropological Records in t... more Six Milllon Years of Volcanic, Tectonic,Paleoenvironmental, and Paleoanthropological Records in the Middle Awash Region of Ethiopia.
Proceedings of the National Academy of Sciences, 2021
Body and canine size dimorphism in fossils inform sociobehavioral hypotheses on human evolution a... more Body and canine size dimorphism in fossils inform sociobehavioral hypotheses on human evolution and have been of interest since Darwin’s famous reflections on the subject. Here, we assemble a large dataset of fossil canines of the human clade, including all available Ardipithecus ramidus fossils recovered from the Middle Awash and Gona research areas in Ethiopia, and systematically examine canine dimorphism through evolutionary time. In particular, we apply a Bayesian probabilistic method that reduces bias when estimating weak and moderate levels of dimorphism. Our results show that Ar. ramidus canine dimorphism was significantly weaker than in the bonobo, the least dimorphic and behaviorally least aggressive among extant great apes. Average male-to-female size ratios of the canine in Ar. ramidus are estimated as 1.06 and 1.13 in the upper and lower canines, respectively, within modern human population ranges of variation. The slightly greater magnitude of canine size dimorphism in ...
The suid sample from the Konso Formation spans the ~1.9 Ma to ~0.85 Ma time period, although very... more The suid sample from the Konso Formation spans the ~1.9 Ma to ~0.85 Ma time period, although very few fossils are known from strata younger than ~1.25 Ma. The Konso fossil assemblage at ~1.9 Ma includes Notochoerus clarki, Metridiochoerus andrewsi, Kolpochoerus limnetes and K. cf. majus. The Konso N. clarki represents one of the youngest known occurrences of this taxon. Kolpochoerus cf. majus is common throughout the Konso Formation sequence. Its facial and dental morphology suggests a condition broadly intermediate between earlier K. phillipi and later K. majus. At Konso, the ~1.9 Ma K. limnetes is continued by fragmentary ~1.75 Ma to ~1.45 Ma fossils attributed to K. limnetes/olduvaiensis. Fossils younger than ~1.45 Ma are attributed to K. olduvaiensis based on third molar development and advanced facial morphology. Metridiochoerus andrewsi continues from ~1.9 Ma to ~1.75 Ma, but was replaced by M. compactus and M. hopwoodi by ~1.6 Ma. Metridiochoerus modestus is documented after ~1.45 Ma, so that three species of Metridiochoerus co-occur. The few fossils from ~0.85 Ma include fragments of K. olduvaiensis, M. modestus and cf. Phacochoerus.
The palaeobiological record of 12 million to 7 million years ago (Ma) is crucial to the elucidati... more The palaeobiological record of 12 million to 7 million years ago (Ma) is crucial to the elucidation of African ape and human origins, but few fossil assemblages of this period have been reported from sub-Saharan Africa. Since the 1970s, the Chorora Formation, Ethiopia, has been widely considered to contain ~10.5 million year (Myr) old mammalian fossils. More recently, Chororapithecus abyssinicus, a probable primitive member of the gorilla clade, was discovered from the formation. Here we report new field observations and geochemical, magnetostratigraphic and radioisotopic results that securely place the Chorora Formation sediments to between ~9 and ~7 Ma. The C. abyssinicus fossils are ~8.0 Myr old, forming a revised age constraint of the human-gorilla split. Other Chorora fossils range in age from ~8.5 to 7 Ma and comprise the first sub-Saharan mammalian assemblage that spans this period. These fossils suggest indigenous African evolution of multiple mammalian lineages/groups betwe...
The vertebrate fossil localities of the Chorora Formation, Ethiopia, comprise one of only a few s... more The vertebrate fossil localities of the Chorora Formation, Ethiopia, comprise one of only a few sub-Saharan African paleontological research areas that illuminate Late Miocene African mammalian and primate evolution. Field work at Chorora since 2007 has resulted in the establishment of new vertebrate fossil localities and a revised chronostratigraphic framework. The new Chorora Formation fossils include the earliest known records of Cercopithecinae, Hippopotaminae, and Leporidae in Africa. Two lineages of hipparionins are recognized at Chorora, a larger and smaller morph, forming potential phyletic links between the earlier Samburu Hills hipparionins and later Eurygnathohippus turkanensis and E. feibeli from Lothagam, Kenya. The Chorora colobines are larger than the >9 Ma Microcolobus and morphologically conservative with only moderate molar cusp notches. The Chorora cercopithecines represent the earliest documented occurrence of the subfamily.
Clarifying the geographic, environmental and behavioural contexts in which the emergence of anato... more Clarifying the geographic, environmental and behavioural contexts in which the emergence of anatomically modern Homo sapiens occurred has proved difficult, particularly because Africa lacked adequate geochronological, palaeontological and archaeological evidence. The discovery of anatomically modern Homo sapiens fossils at Herto, Ethiopia, changes this. Here we report on stratigraphically associated Late Middle Pleistocene artefacts and fossils from fluvial and lake margin sandstones of the Upper Herto Member of the Bouri Formation, Middle Awash, Afar Rift, Ethiopia. The fossils and artefacts are dated between 160,000 and 154,000 years ago by precise age determinations using the 40Ar/39Ar method. The archaeological assemblages contain elements of both Acheulean and Middle Stone Age technocomplexes. Associated faunal remains indicate repeated, systematic butchery of hippopotamus carcasses. Contemporary adult and juvenile Homo sapiens fossil crania manifest bone modifications indicati...
Homo erectusPleistocene Evidence from the Middle Awash, Ethiopia, 2009
... these marks. FIGURE 13.2 Excavation of the Daka calvaria BOU-VP-2/66 on the day of discovery.... more ... these marks. FIGURE 13.2 Excavation of the Daka calvaria BOU-VP-2/66 on the day of discovery. The low hills on the skyline are the Dulu Ali basalts and sediments, and the site of Aramis lies beyond these hills. Daka Member ...
Proceedings of the National Academy of Sciences, 2021
Significance Understanding the evolution, dispersals, behaviors, and ecologies of early African H... more Significance Understanding the evolution, dispersals, behaviors, and ecologies of early African Homo sapiens requires accurate geochronological placement of fossils and artifacts. We introduce open-air occurrences of such remains in sediments of the Middle Awash study area in Ethiopia. We describe the stratigraphic and depositional contexts of our discoveries and demonstrate the effectiveness of recently developed uranium-series dating of ostrich eggshell at validating and bridging across more traditional radioisotopic methods ( 14 C and 40 Ar/ 39 Ar). Homo sapiens fossils and associated Middle Stone Age artifacts are placed at >158 and ∼96 ka. Later Stone Age occurrences are dated to ∼21 to 24 ka and ∼31 to 32 ka, firmly dating the upper portion of one of the longest records of human evolution.
This book presents a beautiful photo collection of the Konso stone tools, the Acheulean artifacts... more This book presents a beautiful photo collection of the Konso stone tools, the Acheulean artifacts. These artifacts include the world's oldest stone tools shaped to preconceived form. The volume illustrates early stone tool technology and its development from 1.75 to fewer than 1 million years ago.
The Hippopotamidae have been a major component of the African wetland fauna for the last 7 millio... more The Hippopotamidae have been a major component of the African wetland fauna for the last 7 million years, following the 'Hippopotamine Event,' i.e., the sudden emergence in the fossil record of the subfamily Hippopotaminae, including both extant species. The general dearth of African fossiliferous deposits dated between 9.5 Ma and 7.5 Ma concealed until now the evolution that led to the Hippopotamine Event and the subsequent success of these large semiaquatic herbivores. Part of this evolution is unveiled by the hippopotamid dental remains found at Chorora, a late Miocene site of the southern Afar Depression in Ethiopia spanning most of the fossil-depleted time interval. Although fragmentary, these remains represent a new, mid-sized hippopotamid species dated to ca. 8 Ma, as well as a somewhat younger, larger form. A cladistic analysis of a large array of cetartiodactyls indicates that the Chorora taxa were basal to the latest Miocene hippopotamines. The new species displays a mosaic of dental characters that support the attribution of the new species to a new genus within Hippopotaminae. The new fossils also clarify the course of early hippopotamine dental evolution. The Chorora hippopotamids suggest that transition to a marked abundance of hippopotamines with their unique dental pattern in African ecosystems occurred within a relatively short time interval, most probably between 8 Ma and 7.5 Ma. http://zoobank.org/urn:lsid:zoobank.org:pub:47B9381F-E3B5-40C9-B9AB-51CC3D0D3A8A
Proceedings of the National Academy of Sciences, 2020
Significance We report a rare example of a 1.4-million-y-old large bone fragment shaped into hand... more Significance We report a rare example of a 1.4-million-y-old large bone fragment shaped into handaxe-like form. This bone tool derives from the Konso Formation in southern Ethiopia, where abundant early Acheulean stone artifacts show considerable technological progression between ∼1.75 and <1.0 Mya. Technological analysis of the bone tool indicates intensive anthropogenic shaping. Edge damage, polish, and striae patterns are consistent with use in longitudinal motions, such as in butchering. The discovery of this bone handaxe shows that advanced flaking technology, practiced at Konso on a variety of lithic materials, was also applied to bone, thus expanding the known technological repertoire of African Early Pleistocene Homo .
Six Milllon Years of Volcanic, Tectonic,Paleoenvironmental, and Paleoanthropological Records in t... more Six Milllon Years of Volcanic, Tectonic,Paleoenvironmental, and Paleoanthropological Records in the Middle Awash Region of Ethiopia.
Proceedings of the National Academy of Sciences, 2021
Body and canine size dimorphism in fossils inform sociobehavioral hypotheses on human evolution a... more Body and canine size dimorphism in fossils inform sociobehavioral hypotheses on human evolution and have been of interest since Darwin’s famous reflections on the subject. Here, we assemble a large dataset of fossil canines of the human clade, including all available Ardipithecus ramidus fossils recovered from the Middle Awash and Gona research areas in Ethiopia, and systematically examine canine dimorphism through evolutionary time. In particular, we apply a Bayesian probabilistic method that reduces bias when estimating weak and moderate levels of dimorphism. Our results show that Ar. ramidus canine dimorphism was significantly weaker than in the bonobo, the least dimorphic and behaviorally least aggressive among extant great apes. Average male-to-female size ratios of the canine in Ar. ramidus are estimated as 1.06 and 1.13 in the upper and lower canines, respectively, within modern human population ranges of variation. The slightly greater magnitude of canine size dimorphism in ...
The suid sample from the Konso Formation spans the ~1.9 Ma to ~0.85 Ma time period, although very... more The suid sample from the Konso Formation spans the ~1.9 Ma to ~0.85 Ma time period, although very few fossils are known from strata younger than ~1.25 Ma. The Konso fossil assemblage at ~1.9 Ma includes Notochoerus clarki, Metridiochoerus andrewsi, Kolpochoerus limnetes and K. cf. majus. The Konso N. clarki represents one of the youngest known occurrences of this taxon. Kolpochoerus cf. majus is common throughout the Konso Formation sequence. Its facial and dental morphology suggests a condition broadly intermediate between earlier K. phillipi and later K. majus. At Konso, the ~1.9 Ma K. limnetes is continued by fragmentary ~1.75 Ma to ~1.45 Ma fossils attributed to K. limnetes/olduvaiensis. Fossils younger than ~1.45 Ma are attributed to K. olduvaiensis based on third molar development and advanced facial morphology. Metridiochoerus andrewsi continues from ~1.9 Ma to ~1.75 Ma, but was replaced by M. compactus and M. hopwoodi by ~1.6 Ma. Metridiochoerus modestus is documented after ~1.45 Ma, so that three species of Metridiochoerus co-occur. The few fossils from ~0.85 Ma include fragments of K. olduvaiensis, M. modestus and cf. Phacochoerus.
The palaeobiological record of 12 million to 7 million years ago (Ma) is crucial to the elucidati... more The palaeobiological record of 12 million to 7 million years ago (Ma) is crucial to the elucidation of African ape and human origins, but few fossil assemblages of this period have been reported from sub-Saharan Africa. Since the 1970s, the Chorora Formation, Ethiopia, has been widely considered to contain ~10.5 million year (Myr) old mammalian fossils. More recently, Chororapithecus abyssinicus, a probable primitive member of the gorilla clade, was discovered from the formation. Here we report new field observations and geochemical, magnetostratigraphic and radioisotopic results that securely place the Chorora Formation sediments to between ~9 and ~7 Ma. The C. abyssinicus fossils are ~8.0 Myr old, forming a revised age constraint of the human-gorilla split. Other Chorora fossils range in age from ~8.5 to 7 Ma and comprise the first sub-Saharan mammalian assemblage that spans this period. These fossils suggest indigenous African evolution of multiple mammalian lineages/groups betwe...
The vertebrate fossil localities of the Chorora Formation, Ethiopia, comprise one of only a few s... more The vertebrate fossil localities of the Chorora Formation, Ethiopia, comprise one of only a few sub-Saharan African paleontological research areas that illuminate Late Miocene African mammalian and primate evolution. Field work at Chorora since 2007 has resulted in the establishment of new vertebrate fossil localities and a revised chronostratigraphic framework. The new Chorora Formation fossils include the earliest known records of Cercopithecinae, Hippopotaminae, and Leporidae in Africa. Two lineages of hipparionins are recognized at Chorora, a larger and smaller morph, forming potential phyletic links between the earlier Samburu Hills hipparionins and later Eurygnathohippus turkanensis and E. feibeli from Lothagam, Kenya. The Chorora colobines are larger than the >9 Ma Microcolobus and morphologically conservative with only moderate molar cusp notches. The Chorora cercopithecines represent the earliest documented occurrence of the subfamily.
Clarifying the geographic, environmental and behavioural contexts in which the emergence of anato... more Clarifying the geographic, environmental and behavioural contexts in which the emergence of anatomically modern Homo sapiens occurred has proved difficult, particularly because Africa lacked adequate geochronological, palaeontological and archaeological evidence. The discovery of anatomically modern Homo sapiens fossils at Herto, Ethiopia, changes this. Here we report on stratigraphically associated Late Middle Pleistocene artefacts and fossils from fluvial and lake margin sandstones of the Upper Herto Member of the Bouri Formation, Middle Awash, Afar Rift, Ethiopia. The fossils and artefacts are dated between 160,000 and 154,000 years ago by precise age determinations using the 40Ar/39Ar method. The archaeological assemblages contain elements of both Acheulean and Middle Stone Age technocomplexes. Associated faunal remains indicate repeated, systematic butchery of hippopotamus carcasses. Contemporary adult and juvenile Homo sapiens fossil crania manifest bone modifications indicati...
Homo erectusPleistocene Evidence from the Middle Awash, Ethiopia, 2009
... these marks. FIGURE 13.2 Excavation of the Daka calvaria BOU-VP-2/66 on the day of discovery.... more ... these marks. FIGURE 13.2 Excavation of the Daka calvaria BOU-VP-2/66 on the day of discovery. The low hills on the skyline are the Dulu Ali basalts and sediments, and the site of Aramis lies beyond these hills. Daka Member ...
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