The time interval spanning approximately 4-3 million years ago (Ma) brackets the known occurrences of Australopithecus afarensis, which recently has been joined in this interval by two new taxa, Kenyanthropus platyops and Australopithecus bahrelghazali from Kenya and Chad respectively. The proliferation of hominid taxa is a consequence of recent paleontological field efforts in the African Pliocene, but we have very limited understanding of the diversity, variability and biogeography of these taxa in the roughly 1 million years following the earliest occurrences of A. afarensis around 4 Ma in the middle Awash deposits of Ethiopia and at Laetoli in Tanzania to the denser occurrences about 3 Ma at Hadar.
The Pliocene sediments at Dikika, Ethiopia, just south of Hadar, present an excellent opportunity to recover more fossil data spanning this crucial time period – data that could help resolve the ecological relationships among the contemporaneous species and shed light on their phylogenetic relationships to ancestral and descendent taxa. Sediments are extensive and efforts from four preliminary field seasons at Dikika indicate that the region is extremely fossiliferous and has already yielded two exciting hominid discoveries. The project has been very conservative in fossil collection, choosing instead to first develop a thorough understanding of the geology and physical geography of the region.
We are conducting our annual fieldwork with the following objectives in mind:
Detailed mapping and survey of the study area: our goal is to elevate to a new level the standard for mapping the geological and geographical provenience of all fossil discoveries.
- Documenting the paleoanthropological content of the Basal Member of the Hadar Formation: the objective here is twofold, first to recover additional skeletal elements from the previous hominid finds through more intensive screening of the localities, and secondly to initiate paleontological surveys in new areas, with the development of our knowledge of the stratigraphy of the region.
- Establishing the intrabasinal geological, paleoenvironmental and taphonomic context of Dikika: in order to extend our knowledge beyond just the phylogenetics and systematics of hominids we will also examine the paleoenvironmental context within the basin following two complimentary tracks, geological and paleobiological.
- Interbasinal paleoecological comparisons: comparison with related taxa requires collaboration and comparison across basins. Data collected in the course of this project will provide input to interdependent research projects across basins in order to establish how the Dikika fauna and geology fit into the larger landscape of East African paleobiogeography and paleoecology.