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Hominid Sites and Paleo Lakes Drilling Project (HSPDP)

Kenya Human Origins Drilling1

Drilling for Human Origins

Andrew S. Cohen University of Arizona

We participated in this scientific core drilling services project to obtain sediment cores from several of the most important fossil hominin and early Paleolithic artifact sites in the world, located in Kenya and Ethiopia. Our objective was to drill in near-continuous lacustrine sedimentary sequences close to areas of critical importance for understanding hominin phylogeny, and covering key time intervals for addressing questions about the role of earth system (and especially climate)forcing in shaping human evolution. These sites are all currently on-land, but consist of thick lacustrine sedimentary sequences with rapid deposition rates. Therefore, the sites combined the attributes of relatively low cost targets (in comparison with open water, deep lake sites) and the potential for highly continuous and informative paleoenvironmental records obtainable from lake beds.

STUDY SITES

Tugen Hills – June 1, 2013

W. Turkana – June 21, 2013

Chew Bahir – November 6, 2014

Northern Awash – February 23, 2014

L. Magadi – June 15, 2014

BACKGROUND

Since the 1980s paleoanthropologists and geologists have made major strides in attempting to link our understanding of human origins with the tempo and mode of climate change and variability on the Earth (e.g. Vrba, 1988, Potts, 1996, deMenocal, 2004). Systematic efforts have addressed the key question of why hominin evolution displays a pulsed pattern, with well-defined periods of extensive speciation or extinction, cultural change and geographic expansion, interspersed with long periods when relatively little change seems to occur. Is this the result of broad forcing effects of either directional environmental change (climate, etc.), the result of changes in the variability of local or regional environments, or yet-unrecognized forcing mechanism(s). These efforts have proceeded along two fairly well established paths:

  • Correlating broad-scale patterns of hominin phylogeny with the global beat of climate variability, especially the rhythm of orbital forcing cycles, as recorded in the continuous archives of deep-sea sediment cores (e.g. DeMenocal, 1995 and 2004), or,
  • Correlating regional shifts in the hominin fossil and archaeological record with more local patterns of paleoenvironmental change, inferred from continental outcrop records of paleosols, lake beds and non-hominin fossils (e.g. Bobe and Behrensmeyer, 2004; Quade et al, 2004).

 

Kenya Human Origins Drilling

Figure 1. Outcrop of Middle Pliocene diatomaceous lake beds at Ledi Geraru, northern Afar region of Ethiopia, typical of the target lithologies for drilling in this area (photo: Roy Johnson.)

 

 

 

 

 

 

 

 

 

 

 

 

 

Our objective is to develop a new community-wide effort to address this central question about human origins, combining the strengths of both of the approaches above, and avoiding some of their inherent weaknesses. Our approach is to promote a concerted effort to obtain drill core records from near-continuous sedimentary sequences located close to areas of critical importance for understanding hominin evolution, focused around critical time intervals for our core question above.

Drill cores, with their continuity and potential preservation of organic matter, fossils and other archives that are frequently degraded or disjunct on the outcrop exposures, provide a record that will vastly improve understanding of environmental history in the places and times where various species of hominins lived. Obtaining such records from the continental interiors will provide a spatially resolved record at the landscape scale, much more localized (and with much higher temporal resolution) than the regional/global climate signals preserved in deep sea core records. Finally, because the largest number of critical events in hominin phylogeny occurred in Africa, such a drilling campaign should start in that continent. The rationale for such a research program was defined at a recent NSF/DOSECC-funded conceptual workshop “Paleoclimates and Human Evolution” (Cohen et al., 2006; Potts, REF).

Our approach to the use of scientific drilling to address questions of human origins has a precedent in the 2005 drilling campaign at Lake Malawi (e.g. Scholz et al., 2006; 2007; Cohen et al., 2007, Brown et al. 2007, 2008). This project yielded near-continuous core records spanning the last few hundred thousand years, an important time intervals in human prehistory. It also provided a “proof-of-concept” that high-quality core records can be retrieved from African lake deposits with profound implications for the connection between climate and human prehistory.

We now propose to conduct a scientific drilling campaign at four sites of outstanding importance for addressing questions of linkages between human origins and paleoenvironmental history:

  • The Awash River Valley-Ledi Geraru area, northern Afar area of Ethiopia (Middle Pliocene; Figure 1)
  • The West Turkana area, northern Kenya (Plio-Pleistocene)
  • The Olorgesailie area, southern Kenya (Pleistocene)
  • Lake Magadi, southern Kenya (Pleistocene)

As an outcome of this drilling project we will be able to:

  • Test the similarity between hominin site records within local depocenters and existing lake/deep sea core records using similar types of core data sets. By linking the site records to each other where they overlap (e.g. Olorgesailie and Magadi) we will be able to tease out which aspects of the paleoenvironmental records are a function of local hydrology and which are regional signals.
  • Identify climate “surprises” such as major, abrupt climate shifts or short duration events of wide spread impact, which may have played a role in shaping human evolutionary events or hominin species demography (e.g. Cohen et al., 2007).
  • Test hypotheses linking local environmental conditions/change/variability to adaptations (physical and cultural) (e.g. Potts, 1996 and in press). Our records will allow us to evaluate the records of terrestrial climate at key hominin sites through intervals of changing modes of variability in marine records. Marine records and solar insolation forcing suggest modal periods of high environmental variability, which Potts (1996 and in press) has argued should lead to pulses of evolutionary innovation. Whether orbitally modeled periods of high and low climate variability, which are well recorded in marine cores, are also the primary drivers of environmental variation in the African continental tropics remains to be tested, and would be an outcome of our drilling campaign.

As of late 2008 drilling funds for this project have not yet been secured. However, funding has been provided by NSF to conduct initial site and logistics surveys, including the acquisition of subsurface geophysical data (Figure 2) and from NSF and ICDP to hold a drilling workshop to discuss the target localities and other possible future drilling sites for collecting paleoclimate information relevant to human evolution.

 

Kenya Human Origins Drilling1

Figure 2. Reflection seismic survey of Plio-Pleistocene sediments at West Turkana (June 2008). Preparing to shoot using a Land Cruiser mounted accelerated weight drop system (photo: Craig Feibel)

 

 

 

 

 

 

 

 

 

 

 

 

 

References:

Bobe, R. and Behrensmeyer, A.K. 2004, The expansion of grassland ecosystems in Africa in relation to mammalian evolution and the origin of the genus Homo. Palaeogeography, Palaeoclimatology, Palaeoecology 207: 399-420.

Brown, E.T. Johnson, T.C., Scholz, C.A., Cohen, A.S. and King, J. 2007, Abrupt Change in Tropical African Climate Linked to the Bipolar Seesaw Over the Past 55,000 Years. In Press, Geophys. Res. Let. 34, L20702, doi:10.1029/2007/GL031240.

Brown, E.T., Johnson, T.C., Scholz, C.A., Cohen, A.S. and King, J.W., 2008, Reply to comment by Yannick Garcin on ‘‘Abrupt change in tropical African climate linked to the bipolar seesaw over the past 55,000 years’’ Geophysical Research Letters, Vol. 35, L04702, doi:10.1029/2007GL033004, 2008.

Cohen, A.S., Ashley, G.M., Potts, R., Behrensmeyer, A.K., Feibel, C., and Quade. J., 2006, Paleoclimate and Human Evolution Workshop. EOS 87:161.

Cohen, A.S., Stone, J.R., Beuning, K.R., Park, L.E., Reinthal, P.N., Dettman, D., Scholz, C.A., Johnson, T.C., King, J.W., Talbot, M.R., Brown, E.T., and Ivory, S.J., 2007 Ecological Consequences of Early Late-Pleistocene Megadroughts in Tropical Africa. Proc. Nat. Acad. Sci. 104:16422-16427.

deMenocal, P.B., 1995, Plio-Pleistocene African climate. Science 270:53-59.

deMenocal, P. 2004, African climate change and faunal evolution during the Plio-Pleistocene. EPSL 220:3-24.

Potts, R., 1996, Evolution and climate variability. Science 273:922-923.

Potts, R., in press Environmental context of Pliocene human evolution in Africa. In: Hominin Environments in the East African Pliocene: An Assessment of the Faunal Evidence (R. Bobe, Z. Alemseged, and A.K. Behrensmeyer, eds.), Kluwer, New York.

Potts, R., 2007, Paleoclimate and human evolution. Evolutionary Anthropology 16:1-3.

Quade, J., Levin, N., Semaw, S., Stout, D., Renne, P., Rogers, M., Simpson, M., 2004, Paleoenvironments of the earliest stone toolmakers, Gona, Ethiopia. GSA Bull. 116:1529-1544.

Scholz, C.A., Cohen, A.S., Johnson, T.C. and King, J. W., 2006 The 2005 Lake Malawi Scientific Drilling Project. Scientific Drilling Mar 2006:17-19, doi:10.2204/iodp.sd.1.04.2006.

Scholz, C.A., Johnson, T.C., Cohen, A.S., King, J.W., Peck, J., Overpeck, J.T., Talbot, M.R., Brown, E.T., Kalindekafe, L., Amoako, P., et al. 2007, East African megadroughts between 135-75 kyr ago and implications for early human history Proc. Nat. Acad. Sci. 104:16416-16421.

Vrba, E.,S 1988, Late Pliocene climate events and hominid evolution. In Grine, F.(ed) Evolutionary History of the “Robust” Australopithicines. Aldine Press, N.Y., pp. 405-426.