The Smithsonian’s Human Origins Program team was led by Dr. Rick Potts in collaboration with the National Museums of Kenya and worked with DOSECC to obtain the first long climate core from an early human fossil site. The goal is to better understand the climate environments connected with the origin of our species in Africa, along with the preceeding events.
The core was taken on a flat, grassy plain in the previously unexplored southern region of the Olorgesailie basin at the prehistoric site of Olorgesailie, located in the southern Kenya Rift Valley. Previous excavations documented fundamental changes in the behavior of our early human ancestors over the past 500,000 years. However, many tens of thousands of years of this period are missing due to the erosion of sediment layers visible above ground in the Olorgesailie region. Drilling allowed researches to recover sediment layers underground that preserve a complete, high-precision record of rainfall, temperature, vegetation, and environmental stresses – and how these changed over time – during the critical transitions involved in the origin and evolution of Homo sapiens.
Strategically-placed drill cores will capture the continuous, fine structure of the environmental record, which is vitally important in studying questions about changes in Earth’s climate, environment, and geological forces. The cores will allow sufficiently high resolution to study short-duration events and processes (e.g., seasonality, interannual change, volcanic episodes, tectonic events) and to see how these relate to environmental changes over evolutionary time scales that may have influenced the evolution of human adaptations.
This project is part of the Smithsonian’s Human Origins Program and relates to the Hominid Sites and Paleo Lakes Drilling Project HSPDP. This scientific drilling program drills ancient lake sediments in eastern Africa and other regions in order to obtain long climate records in the areas once inhabited by early hominins. This allows researches to better understand worldwide, regional, and local climate dynamics relevant to the time periods and the regions where human evolutionary change took place. This allows us to explore the parallels and connections between environmental change and human origins
From September 2 to October 4, 2012, the effort to recover the core was successfully carried out. The core, lifted from two boreholes in segments 3-meters long, represents a detailed record of lake sedimentation. Through the plastic liners in which the core was recovered, fine laminations of diatomite and clay lake deposits can be seen, along with inputs of fine silts and sands – all of which we believe capture the environmental dynamics of this region of the East African Rift Valley over approximately the past 500,000 years.
The cores extend down to 166m below the ground surface, and provide evidence of the ancient lake that had not previously been visible but that we suspected must have existed in the drilling area.
Unexpected challenges in recovering these cores occurred, but all were solved so that the project started and was completed on time. These challenges included initial difficulties in getting drilling rods, core liners, and other critical supplies into Kenya, a rupture in the water pipeline in the closest town of Magadi, which was to supply the drilling water at no cost to the project, and damage to the drilling rods during the first several days of drilling due to our local team’s unfamiliarity with the specialized rods sent from the U.S. for this project. Project funding along with the expertise assembled at the drill site were instrumental in meeting and solving these challenges as they arose.
Future Study and Implications
The Olorgesailie team is excited about the results of the core drilling. Knowledge gained from our two decades of study elsewhere in the Olorgesailie region imply that the layers of lake sediment in the cores represent the past 500,000 years in high-resolution. We will employ direct methods of dating the volcanic tephra in the core. If our current understanding of the age range is correct, the core will give us the most exact record of climatic stresses and ecological change in East Africa during four key chapters in human evolution:
The earliest transition from handaxe technology to innovative technologies, including projectiles (i.e., being able to hunt at a distance); this transition is recorded at Olorgesailie between 500,000 and 300,000 years ago;
The origin of the modern East African biota, which occurred in the same era;
The origin of our species, around 200,000 years ago;
An era of low population size or population crash in Homo sapiens in Africa 100,000 to 70,000 years ago, just prior to the global expansion of our species.
Investigating the environmental challenges of these eras will allow us to test and determine as best as possible how evolutionary processes of survival helped shape the human species.
The first of two steps in this project have been completed. The ultimate goal is not only to recover the cores but to produce well-studied cores, which we believe will yield benchmark scientific papers in the study of human origins. In late April 2013, Potts will assemble an international team of 20 to 25 scientists to open the cores, which will be housed at the international lake core facility, LacCore, at the University of Minnesota, Minneapolis. At the week-long workshop, our scientific team will describe and sample the cores for detailed analysis, followed by 12-24 months of laboratory studies, project workshops, synthesis of results, and the writing of publications.
Support from the William H. Donner Foundation (New York); the Ruth and Vernon Taylor Foundation (Montana); and the Peter Buck Fund for Human Origins Research (Smithsonian) has been indispensable in enabling us to achieve the first step in this project. Projects are also being planned by other research teams to try to recover ancient lake cores from other famous fossil sites in East Africa.
Twenty-two researchers from around the world participated in the Olorgesailie core workshop. The team collected samples every 48 centimeters in order to carry out many different kinds of environmental analysis.