Editor’s Note: John Rowan has previously posted from a field site in Ledi-Gareru and is now working with specimens at the National Museum in Addis Ababa. Just as primary field research is an important component of anthropological work, comparative analysis and lab research—which may not be as exotic or seemingly adventurous as living in a tent in the Afar—can be as satisfying and exciting to our students (and scientists)! So, here is a bit of a twist on “Notes from the Field.” I hope you enjoy it—I think you will!
After a short hiatus in Arizona, I have returned to Ethiopia. I arrived in Addis Ababa five days ago and the city has been buzzing with excitement as the African Union (AU) is celebrating their 50th anniversary at the AU headquarters in Addis this week. Heads of State from all over the continent and all over the world, including US Secretary of State John Kerry, have flown to Ethiopia’s capital to celebrate this historic moment. The traffic is worse than usual as police escorts cut through never-ending lines of cars and pedestrians.
For the next few weeks I’ll be living in Addis at the IHO house and working in the research collections at the Ethiopian National Museum. Along with AU festivities, the museum is also celebrating the return of Lucy, the famous female skeleton of Australopithecus afarensis, as she was returned to Ethiopia less than a month ago from her worldwide tour. Don Johanson, Lucy’s discoverer and IHO founding director, and Zeresenay Alemseged, former IHO postdoc and current IHO affiliate, flew to Addis to welcome back Ethiopia’s paleoanthropological gemstone. (Editor: To see a short (2 minute) Ethiopia television piece on “Lucy’s” return, click here; to see a longer piece (25 minutes), click here.)
While the AU and Lucy celebrations are a nice distraction, as the token paleontology student at IHO, I’ll be devoting most of my time here to the nonhominin fossils from Hadar and Ledi-Geraru. Primarily, I’ll be working on the “ungulates,” or hoofed mammals, including giraffes, hippos, suids (pigs), elephants, equids (horses), rhinos, and, in particular, bovids (antelope). In addition to IHO’s fossil sites, I’ll also be working with fossil bovids from the Omo and Middle Awash collections.
As noted above, I am particularly interested in the fossil record of African antelope. Bovids are an excellent group for macroevolutionary and paleoecological studies because they are geographically and temporally widespread, are abundant in Plio-Pleistocene fossil deposits, exhibit tribal dietary and habitat preferences, and are relatively specious, represented by roughly 140 extant species. But what does any of this have to do with human evolution? The data collected during my stay in Addis will help provide the broader ecological and environmental context of human evolution in Ethiopia, along with providing insights into the tempo and mode of evolutionary processes in a mammalian group that overlaps with the hominin lineage in body size, dietary and habitat preference, and geographic distribution. While it may seem bizarre to attempt to gain insights into evolutionary patterns of the human lineage through that of nonhuman mammals, several authors, primarily Elisabeth Vrba (Yale U.), have proposed that most origination and extinction events across mammalian groups have occurred in sync due to known climatic or tectonic changes over the last few million years in Africa (aptly termed the “turnover pulse” hypothesis). This hypothesis implies that hominins should fit to the general pattern of origination and extinction documented in other mammals throughout the African fossil record. Not surprisingly, this appears to be the case. For example, two of the most well-documented turnovers in African fauna occur about 2.8 mya and 1.8 mya, two dates that in human evolution correspond to the disappearance of Australopithecus afarensis (a species that had previously persisted for almost one million years) and the evolution of Homo erectus (an important grade shift in human evolution when many behavioral and anatomical characteristics of humans first evolve), respectively.
Similarly, the commonness of bovids in the Plio-Pleistocene record provides us with insights into mammalian biogeography during this time and allows us to generate hypotheses about dispersal corridors and centers of endemism for rarer taxa that are less common in the fossil record, including hominins. Also, bovids are excellent tools for reconstructing early hominin habitats since they are characterized by distinct habitat preferences based on tribe (tribe is a low taxonomic level of organization—it groups similar animals together below the level of subfamily or family). For example, the recovery of reduncin bovids (e.g., kobs) at fossil sites indicate the presence of well-watered habitats and some waterlogged grassland, while the recovery of aepycerotins (impala) indicate ecotonal habitats where savannah grasses border woodland and more densely vegetated landscapes. The fossil record of antelope provides many other useful tools that help elucidate the evolutionary, ecological, and environmental context of human evolution, but for the sake of brevity this is all that I’ll discuss (for now).
So, that’s all for now—my next post should be coming soon and I’ll talk about my trip to the Ethiopian Highlands, from which I just returned, where we observed some of the rarest monkeys in the world—gelada baboons.