Browsing by Author "Wynn, Jonathan G."
Now showing 1 - 4 of 4
Results Per Page
Sort Options
- Fossils from Mille-Logya, Afar, Ethiopia, elucidate the link between Pliocene environmental changes and Homo originsPublication . Alemseged, Zeresenay; Wynn, Jonathan G.; Geraads, Denis; Reed, Denne; Andrew Barr, W.; Bobe, Rene; McPherron, Shannon P.; Deino, Alan; Alene, Mulugeta; J. Sier, Mark; Roman, Diana; Mohan, JosephSeveral hypotheses posit a link between the origin of Homo and climatic and environmental shifts between 3 and 2.5 Ma. Here we report on new results that shed light on the interplay between tectonics, basin migration and faunal change on the one hand and the fate of Australopithecus afarensis and the evolution of Homo on the other. Fieldwork at the new Mille-Logya site in the Afar, Ethiopia, dated to between 2.914 and 2.443 Ma, provides geological evidence for the northeast migration of the Hadar Basin, extending the record of this lacustrine basin to Mille-Logya. We have identified three new fossiliferous units, suggesting in situ faunal change within this interval. While the fauna in the older unit is comparable to that at Hadar and Dikika, the younger units contain species that indicate more open conditions along with remains of Homo. This suggests that Homo either emerged from Australopithecus during this interval or dispersed into the region as part of a fauna adapted to more open habitats.
- Gorongosa by the sea: First Miocene fossil sites from the Urema Rift, central Mozambique, and their coastal paleoenvironmental and paleoecological contextsPublication . Habermann, Jörg M.; Alberti, Matthias; Aldeias, Vera; Alemseged, Zeresenay; Archer, Will; Bamford, Marion; Biro, Dora; Braun, David R.; Capelli, Cristian; Cunha, Eugenia; da Silva, Maria Ferreira; Luedecke, Tina; Madiquida, Hilario; Martinez, Felipe I.; Mathe, Jacinto; Negash, Enquye; Paulo, Luis M.; Pinto, Maria; Stalmans, Marc; Regala, Frederico Tata; Wynn, Jonathan G.; Bobe, Rene; Carvalho, SusanaThe East African Rift System (EARS) has played a central role in our understanding of human origins and vertebrate evolution in the late Cenozoic of Africa. However, the distribution of fossil sites along the rift is highly biased towards its northern extent, and the types of paleoenvironments are primarily restricted to fluvial and lacustrine settings. Here we report the discovery of the first fossil sites from the Urema Rift at Gorongosa National Park (central Mozambique) at the southern end of the EARS, and reconstruct environmental contexts of the fossils. In situ and surface fossils from the lower member of the Mazamba Formation, estimated to be of Miocene age, comprise mammals, reptiles, fishes, invertebrates, palms, and dicot trees. Fossil and geological evidence indicates a coastal-plain paleoenvironmental mosaic of riverine forest/woodland and estuarine habitats that represent the first coastal biomes identified in the Neogene EARS context. Receiving continental sediment from source terranes west of today's Urema Graben, estuarine sequences accumulated prior to rifting as compound incised-valley fills on a low-gradient coastal plain following transgression. Modern environmental analogues are extremely productive habitats for marine and terrestrial fauna, including primates. Thus, our discoveries raise the possibility that the Miocene coastal landscapes of Gorongosa were ecologically-favorable habitats for primates, providing relatively stable maritime climate and ecosystem conditions, year-round freshwater availability, and food both from terrestrial and marine sources. The emerging fossil record from Gorongosa is beginning to fill an important gap in the paleobiogeography of Africa as no fossil sites of Neogene age have previously been reported from the southernmost part of the EARS. Furthermore, this unique window into past continental-margin ecosystems of central Mozambique may allow us to test key paleobiogeographic hypotheses during critical periods of primate evolution.
- Modern African ecosystems as landscape-scale analogues for reconstructing woody cover and early hominin environmentsPublication . Negash, Enquye W.; Alemseged, Zeresenay; Barr, W. Andrew; Behrensmeyer, Anna K.; Blumenthal, Scott A.; Bobe, René; Carvalho, Susana; Cerling, Thure E.; Chritz, Kendra L.; McGuire, Elizabeth; Uno, Kevin T.; Wood, Bernard; Wynn, Jonathan G.Reconstructing habitat types available to hominins and inferring how the paleo-landscape changed through time are critical steps in testing hypotheses about the selective pressures that drove the emergence of bipedalism, tool use, a change in diet, and progressive encephalization. Change in the amount and distribution of woody vegetation has been suggested as one of the important factors that shaped early hominin evolution. Previous models for reconstructing woody cover at eastern African hominin fossil sites used global-scale modern soil comparative datasets. Our higher-spatial-resolution study of carbon isotopes in soil organic matter is based on 26 modern African locations, ranging from tropical grass-dominated savannas to forests. We used this dataset to generate a new Eastern Africa -specific Woody Cover Model (EAWCM), which indicates that eastern African hominin sites were up to 13% more wooded than reconstructions based on previous models. Reconstructions using the EAWCM indicate widespread woodlands/bushlands and wooded grasslands and a shift toward C4-dominated landscapes in eastern Africa over the last 6 million years. Our results indicate that mixed tree-C4 grass savannas with 10-80% tree cover (but not pure grasslands with <10 % tree cover) dominated early hominin paleoenvironments. Landscapes with these biomes are marked by exceptional heterogeneity, which posed challenges and offered opportunities to early hominins that likely contributed to major behavioral and morphological shifts in the hominin clade. (c) 2024 Elsevier Ltd.
- The environments of Australopithecus anamensis at Allia Bay, Kenya: A multiproxy analysis of early Pliocene BovidaePublication . Dumouchel, Laurence; Bobe, Rene; Wynn, Jonathan G.; Barr, W. AndrewAustralopithecus anamensis, among the earliest fully bipedal hominin species, lived in eastern Africa around 4 Ma. Much of what is currently known about the paleoecology of A. anamensis comes from the type locality, Kanapoi, Kenya. Here, we extend knowledge of the range of environments occupied by A. anamensis by presenting the first multiproxy paleoecological analysis focusing on Bovidae excavated from another important locality where A. anamensis was recovered, locality 261-1 (ca. 3.97 Ma) at Allia Bay, East Turkana, Kenya. Paleoenvironments are reconstructed using astragalar ecomorphology, mesowear, hypsodonty index, and oxygen and carbon isotopes from dental enamel. We compare our results to those obtained from Kanapoi. Our results show that the bovid community composition is similar between the two fossil assemblages. Allia Bay and Kanapoi bovid astragalar ecomorphology spans the spectrum of modern morphologies indicative of grassland, woodland, and even forest-adapted forms. Dietary reconstructions based on stable isotopes, mesowear, and hypsodonty reveal that these bovids' diet encompassed the full C-3 to C-4 dietary spectrum and overlap in the two data sets. Our results allow us to confidently extend our reconstructions of the paleoenvironments of A. anamensis at Kanapoi to Allia Bay, where this pivotal hominin species is associated with heterogeneous settings including habitats with varying degrees of tree cover, including grasslands, bushlands, and woodlands. (C) 2020 Elsevier Ltd. All rights reserved.