The great rifts of Africa are huge pull-apart or tensional zones whose numerous normal faults often drop their central parts thousands of meters below their margins. The Eastern Rift forms a natural hydraulic catchment almost everywhere it is exposed terrestrially. This dynamic system of horsts, grabens, accommodation faults, and uneven land surfaces complexly overlays the rift’s axis. Shallow and ephemeral lakes form in the broken terrain, and rivers fill the lakes with sediment. Continued tectonic activity exposes these sediments and their contents to erosion—and to paleoanthropological research.

With nutrient-rich lakes, stream margins, gallery forests, and grassy sumplands, these geological...

The rich Dakanihylo (Daka) Member of the Bouri Formation in the Afar Rift of Ethiopia is today exposed by active erosion along the northeast slope of the Bouri Peninsula (Figures 1.1 and 1.2). Geochronological results on interbedded volcanic strata indicate an age for these fossiliferous sediments of one million years (Ma). The Daka Member has preserved a very rich array of fossil mammals (>750 collected specimens), including severalHomo erectusspecimens (Vrba 1997; Asfaw et al. 2002; Gilbert 2003b). Numerous Acheulean archaeological localities are documented. This volume presents the fossil content of the Daka Member, provides geological background, and explores...

The Daka Member of the Plio-Pleistocene Bouri Formation, located within the southcentral part of the Middle Awash region of the Afar Rift, encompasses diverse lithologic units dominated by sedimentary deposits with minor interbedded distal tephra markers that crop out along the strike of the NNW-SSE trending and westward-tilted Bouri Fault Block (Figure 2.1). The Bouri Fault Block occurs on the west side of the tectonically controlled Awash River, which flows northward parallel to the Quaternary axial rift zone (de Heinzelin et al. 2000b). The fault block is bounded by Yardi Lake to the southwest and the Awash River floodplain to...

Bovidae comprise the most diverse array of genera for any family represented in the Daka Member. Fossil bovid specimens include more than 25 well-preserved crania and hundreds of dental and horn core specimens. The 17 different genera include extinct and living representatives. The assemblage is especially rich in bovines (Figures 3.1 and 3.2), alcelaphines, and reduncines, but also includes hippotragines, tragelaphines, antilopines, caprines, aepycerotines, neotragines, and possibly ovibovines. The diversity of taxa and the large number of specimens from the Daka Member prevent treatment of Bovidae with as much detail as is given to taxa in other chapters. Some Daka...

Carnivores are less common than most other ordinal taxa in both present communities and those preserved by the fossil record. Th is trend is realized in the small number (10 specimens) of carnivore fossils in the Daka Member. What is lacked in quantity in the assemblage is made up for in quality: the unit has produced one of the best-preserved Pleistocene hyaenid crania known (Figure 4.1). This new specimen, a largeCrocuta,along with remains of bothPantheracf.leoandP. cf.pardus,indicate the presence of numerous large carnivores in the community represented by the Daka Member.

All...

Cercopithecidae is the most speciose and geographically widespread extant nonhuman primate family. It includes two universally accepted extant clades, usually recognized as the subfamilies Cercopithecinae and Colobinae (e.g., Delson 1975; Szalay and Delson 1979; Strasser and Delson 1987; Fleagle 1999; Disotell 2000; Grubb et al. 2003; Brandon-Jones et al. 2004), and occasionally as families (e.g., Jablonski 2002). Many morphological features distinguish these two groups, including soft-tissue features (e.g., Delson 1975; Szalay and Delson 1979; Strasser and Delson 1987; Fleagle 1999; Jablonski 2002). Frost (2001a) provides a relatively complete list. All molecular analyses to date have corroborated this split (e.g., Disotell...

The family Equidae has a rich and well-studied fossil record. The earliest known equids are of the genusHyracotheriumand derive from the early Eocene of North America (MacFadden 1992). Equidae dispersed from North America to the Old World in several events since the Eocene, and theEquusand hipparionine lineages separated in the early middle Miocene (MacFadden 1984; Hulbert and MacFadden 1991). Hipparionines of the genusCormohipparionimmigrated into the Old World during the early late Miocene (ca. 11.2–10.8 Ma) and rapidly dispersed across Eurasia and Africa (Bernor et al. 1996; Woodburne 1996; Bernor et al. 2004). The...

Giraffids are uncommon in the African Plio-Pleistocene fossil record. As is true for most sites, the Daka Member is not particularly rich in giraffe fossils. Remains of Giraffidae include an immatureSivatheriummandible, an immatureSivatheriummaxilla, aSivatheriumupper second premolar, a leftSivatheriummetatarsal, fourGiraffaossicones, and a complete rightGiraffametacarpal.

Possible Giraffids first appear in Africa in the early Miocene with generaClimacoceras, Propalaeoryx,andProlibytherium(Churcher 1978; Gentry 2000b). Established giraffids appear in the middle and late Miocene, and includeCanthumeryx, Palaeotragus, Samotherium, Giraffokeryx, Helladotherium(Churcher 1978; Hamilton 1978; Gentry 2000b). These early genera...

The Daka Member has a number of well-preserved hippopotamid fossils (see Figure 8.1). All are assigned here to the genusHippopotamus.The family Hippopotamidae is represented by two living species:Choeropsis liberiensis(Liberian hippo), a secretive mammal from western equatorial coasts of Africa; andHip. amphibius(common hippo), known from most sub-Saharan countries, a much larger and better known animal. With only two modern representatives, our knowledge of hippo evolutionary history relies mostly on fossils and morphology. However, molecular methods put hippos at the center of a famous controversy. A substantial diversity of molecular analyses identified Cetacea as a modern...

The Daka Member is very rich in elephant fossils (see Figures 9.1 and 9.2). Two crania ofElephas recki reckiwere excavated from the Daka Member during the 1999 and 2002 field seasons. As the cranium from Haïdal, Djibouti Republic, is currently unavailable for study, the two Daka Member crania are the only specimens that can provide us with a rare chance to study details of the cranial anatomy of advancedE. recki.These finds allow revision of ideas concerning the dispersal of palaeoloxodonts from Africa to Eurasia, as well as the taxonomy and spatiotemporal distribution of the Eurasian palaeoloxodont...

Living rhinos are extremely rare and threatened with extinction, but they are the survivors of a once broadly distributed and extremely diverse clade. Rhinos are known from North America and the Old World and have a well-documented fossil record (Prothero et al. 1989). Rhinocerotidae is first reported from the Eocene, and representatives of the family persist through the remaining Cenozoic. Different rhino taxa occupied many different niches. Taxa included small, cursorial forms as well as giraffe-like canopy browsers (Prothero et al. 1989). Modern genera have not changed dramatically since their first appearances in the Pliocene. Daka Member rhinos are attributed...

The Daka Member presents an important assemblage of African suid fossils from approximately 1 Ma. With three nearly complete crania, several more fragmentary crania, and numerous dental specimens, it is one of the best samples ofKolpochoerus majusin the world. It also comprises a moderate sample ofK. olduvaiensisand includes one of the only known complete crania of the taxon (Figures 11.1 and 11.2).Metridiochoerus(including M. modestus) is also present. Daka sediments also contain earlyPhacochoerus.The cooccurrence of and Phacochoerus supports their taxonomic separation.

The taxonomic group Suina includes Suidae (pigs) and Tayassuidae (peccaries). Recent phylogenetic...

While preservation of large mammals in the Daka Member is very good, there are few micromammals and birds preserved. Th ese phylogenetically disparate fossils include a possible stork, a grass rat, and a fish.

Relatively few Pleistocene avian fossils have been described from Ethiopia (Brodkorb 1980; Brodkorb and Mourer-Chauviré 1982). This contrasts with the better-known avifaunas elsewhere in Africa, including those from Olduvai, Die Kelders Cave, and other assemblages. Despite this rarity of data on Ethiopia, the avifauna of Ethiopia’s recent past should be quite interesting, because the modern avifauna of Ethiopia is composed of many rare, endangered, and endemic...

This chapter, the first of four discussing Daka hominid material, presents a detailed ectocranial description of the Daka calvaria (BOU-VP-2/66) and a presentation of other cranial and mandibular specimens from the Daka Member. The other chapters on Daka hominids assess endocranial and internal features (Chapter 14), the systematic placement of the Daka calvaria (Chapter 15), and hominid postcranial remains (Chapter 16).

The first hominid fossils found at Bouri were recovered in 1992 from Daka Member sediments. These remains were femoral specimens and are described in Chapter 16. The first cranial remains were found the following year but were highly fragmentary...

This chapter presents observations made on distortion, subcortical structures, and endocranial features through the use of computed tomographic (CT) imagery of the Daka calvaria. It is organized into two sections: descriptions of the individual cranial vault bones (primarily by WHG) and a description of the endocast (primarily by RH). In addition, several cranial metrics and vault thicknesses were obtained from micro-CT data (presented in Tables 14.1 and 14.2 and in the text). These measurements were derived from coronal, sagittal, and transverse slices using the open-source navigation and display platform OsiriX version 2.1 (Rosset et al. 2004) on images with a...

The basic question of how fossils are allocated to species recurs throughout phylogenetic and taxonomic considerations of early and middle PleistoceneHomo.How are the available specimens best grouped and analyzed? Which specimens or groups of specimens represent direct human ancestors? Answers to these questions are presented to a broad audience, but the recipients may be unfamiliar with nuances and limitations of phylogenetic reconstruction.

Many workers have attempted to distinguish groups among PleistoceneHomo(von Koenigswald and Weidenreich 1939; Wood 1992; Rightmire 1996; Bermúdez de Castro et al. 1997; Foley and Lahr 1997; Gabunia et al. 2002; Mallegni et al....

This chapter outlines the postcranial remains of hominids from the Daka Member. The sample comprises three femora, one tibia, and one talus. The tibia and femora are presented here with descriptions of their preservation and anatomy relative to comparative specimens. The talus is only briefly presented, as it was discovered in late 2005 and has not yet been cleaned for detailed study.

Femora and tibiae of modern humans are variable in morphology (Lovejoy 1975; Grine et al. 1995; Lovejoy et al. 2002). Comparative samples of these elements among PleistoceneHomoare small. Several lower-limb bone features have been posited to...

Deposition of Daka Member fossil remains took place in noncyclothemic lenticular channels (de Heinzelin et al. 2000a). Several episodes of sedimentation are observable, and some paleosols occur in what appears to have been a large river/lake system. The geography of the study area at the time of Daka deposition, with its lakes, rivers, and adjacent subaerial depositional environments, will have had a strong effect on the composition of the faunal assemblage. The components of living communities that accrue into paleontological assemblages are highly biased because the latter are defined by a combination of hydrology and habitat. These geospatial effects are...

This volume has presented the Daka Member as understood in 2007. Work in the Daka Member will continue into the future. The fossil-bearing surfaces of the Bouri area have been systematically surveyed by organized groups of experienced collectors using tightly controlled geospatial techniques to ensure complete coverage. However, each year that the localities here are revisited, several additional fossils are found. We have learned that these subsequent visits always result in diminished rates of overall fossil acquisition (see White 2004); it is therefore certain that future collections will not again yield the abundant, well-preserved fossil mammal collections made at Bouri...