Bone Walks and Paleolandscape Ecology at East Turkana
by Andrew Du.
Many paleoanthropologists are familiar with traditional paleoecological methods where reconstruction is based on taxonomic analyses of non-hominin vertebrate craniodental remains found at a particular site. However, researchers (including myself) at George Washington University, the Smithsonian Institution, and the University of Georgia are interested in a different set of questions. More specifically, we want to know what kind of habitats were hominins inhabiting and what animal communities were they interacting with across the ancient landscape. Were they patterning their behavior in different ways in response to these parameters? Answering these questions can shed more light on key hominin behaviors such as tool-use, resource acquisition strategies, ranging patterns, planning and conceptualization, and social structure.
The issue then becomes one of scale. More conventional paleoecological approaches focus on spatially restricted, site-based analyses, and many look at change through time. However, this does not lend itself to learning about what the ancient landscape was like at any one time period and how it affected hominin behavior. Instead, our methodology focuses on distinct, laterally extensive strata with a limited time component to minimize time averaging, which refers to mixing of paleoecological signals due to superimposed fossil remains generated at different times and potentially different ecological circumstances.
East Turkana, more specifically the Ileret area, in northern Kenya is an ideal place to utilize our methodology and begin to address our research questions. This past summer, Dr. Kay Behrensmeyer (Smithsonian), Dr. René Bobe, David Patterson, Amelia Villaseñor, and myself (all from George Washington University), and Sarah Hakala (University of Georgia) began collecting data using this paleolandscape approach. We recorded vertebrate fossil data from sediments constrained by two distinct, almost contemporaneous ash beds (Lower Ileret Tuff [1.53 million years old] and Northern Ileret Tuff [1.51 million years old]) which are laterally extensive in outcrop. We collected data by conducting systematic “bone walks,” where we walked across an outcrop between the two ash beds and recorded every single bone scrap encountered, not just craniodental or other notable material. This resulted in data that included taxon, skeletal part, side, body size, age, fracture patterns, and more, unbiased by any particular collecting agenda. From these data, we can begin to reconstruct community structure (from taxonomic, body size, and age data) and degree of carnivore competition for prey (from skeletal part and fracture pattern data) in habitats hominins occupied. Ongoing sedimentological and stratigraphic studies by Dr. Kay Behrensmeyer, Amelia Villaseñor, and myself can complement fossil data by reconstructing depositional environments and providing a picture of the physical environment and habitats on the landscape.
Ileret also provides a unique opportunity to study an area where hominins were active (as documented by fossil footprints) but apparently did not discard stone tools. Future field surveying at East Turkana will likely include fossiliferous areas where stone tools are abundant and even areas where a hominin signal (footprints, artifacts, fossil remains) is absent altogether (to serve as an outgroup or “control” sample). By using paleontological and geological methods to investigate these three landscape samples, we can begin to understand the diversity of habitats and animal communities hominins occupied across the landscape and test whether they partitioned their activities to avoid competition with other meat and bone consumers and/or were tethered to certain animal communities and habitats.