Note from the Editor: This begins the newest entry from our “Notes from the Field” series, this time written by one of IHO’s newest doctoral students, John Rowan. In upcoming entries, you will hear more about John’s research interests. I am so interested to hear about what IHO researchers and the international team of scientists are doing in Ledi-Geraru—and I am happy to bring you that news from John.
Greetings from the Afar of Ethiopia—this entry comes from our campsite in the arid scrubland of the Ledi-Geraru research area.
I arrived in Addis Ababa in late December and spent a few weeks working in the National Museum of Ethiopia on Pliocene faunal collections with IHO professor Kaye Reed. The museum was lively as preeminent scientists like Terry Harrison and Yohannes Haile-Selassie were working in the research collections or preparing to head out into the field.
The 2013 field season for the Ledi-Geraru Research Project kicked off on January 9 as we packed up and made the eight-hour trek from Addis Ababa to the Afar. Our team here includes Kaye Reed (IHO/ASU), Ramon Arrowsmith (ASU), Brian Villmoare (George Washington University), David Feary (ASU), three ASU PhD students (Erin DiMaggio, Chalachew Seyoum, and Dominique Garello), and local Afar workers (including the famous Omar Abdullah). The rest of our crew arrives at the end of the month and includes Chris Campisano (IHO/ASU), Lars Werdelin (Swedish Museum of Natural History), and Dave Braun (George Washington University). Every participant forms a different piece of a larger puzzle as we try to collectively reconstruct human evolution in East Africa using lines of evidence from geology, paleontology, and archaeology.
Our current focus is to investigate new fossiliferous exposures that should help fill a significant gap in our understanding of human evolution in East Africa. In the Afar, the Hadar Formation ranges from 3.5mya—2.95mya and is overlain by the Busidima Formation from 2.7mya—160,000ybp; however, sediments ranging from 2.95—2.7mya are missing from the sequence due to an unconformity. For paleoanthropologists, this small slice of time is of great importance because it may be the time when our genus, Homo, originates. To throw light on the origin of Homo, the Ledi-Geraru Research Project was initiated by the late Charlie Lockwood, Kaye Reed, and Ramon Arrowsmith in 2002 as an attempt to clarify the transition from Australopithecus and the emergence of Paranthropus (a bizarre evolutionary off-shoot of robust hominins) and Homo. Along with the earliest members of our own genus, the first stone tools may have appeared during this time period.
The field is always an exciting place of discovery—so far we’ve already deduced that the animals we’re finding in the Ledi-Geraru research area are very different from those at Hadar. In the Hadar Formation, the uppermost deposits demonstrate a general trend towards a more open and arid environment—a change that is in sync with increasing robusticity in Australopithecus afarensis (Lucy’s species). But, as noted above, after 2.95mya, we’re not sure what became of Au. afarensis or the animals with which it shared the landscape with. Ledi-Geraru is showing us that there may have been ecological changes in the Afar around 2.8mya similar to those documented in the Omo-Turkana Basin of northern Kenya and southern Ethiopia. We’ve uncovered new monkeys, bovids, hippos, and other mammalian taxa that may represent immigrants into the Afar from other areas or new and unique species that have evolved from the older Hadar fauna.
That’s all for now—more to come soon!