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The second project looks at the geology of paleolakes in eastern Africa to study ancient climate change and ultimately what that might tell us about how climate affected the development of human ancestors. This research is led by the University of Arizona with lead ASU researchers Chris Campisano, research associate with the Institute of Human Origins and assistant professor in the School of Human Evolution and Social Change, and Kaye Reed, research associate with the Institute of Human Origins and professor in the School of Human Evolution and Social Change. Campisano and Reed are joined by Ramon Arrowsmith, professor in the School of Earth and Space Exploration.
This is the second set of grants for the NSF-FESD program, which is awarding $28 million to five projects focusing on “high risk, high return” research. The goals of the FESD program are to foster an interdisciplinary and multiscale understanding of the interplay among and within the subsystems at work on Earth and to catalyze research in geoscience areas poised for major advances.
The dynamics of Earth system oxygenation
Today, the breathable air we enjoy consists of 21 percent oxygen, in the form of the molecule O2. However, that was not always the case. During the first half of Earth’s history, O2 was nearly absent from the atmosphere and oceans. Then, some 2.45 billion years ago, the level of atmospheric oxygen began to rise – referred to as the “Great Oxidation Event” (GOE).
In the past decade, Anbar and his team have narrowed down the exact timing of this transition to the modern, O2-rich environment. This new $5 million, five-year project, supported by a research team consisting of investigators from five institutions – ASU, MIT, UC Riverside, U. Washington and U. Maryland – will focus on solving the mystery of what caused the rise of atmospheric O2.
“To go from a planet nearly devoid of oxygen at the surface to one that has abundant oxygen is one of the most remarkable transformations that earth has undergone,” said Anbar, a biogeochemist. “It paved the way for our form of life. It’s embarrassing, but we don’t understand why it happened. We don’t even have a solid community consensus as to the cause.”
Anbar’s team will refine and test a number of hypotheses proposed in the past decade.
“Many textbooks say that the rise of oxygen was due to the evolution of photosynthesis. It’s true that photosynthesis is a necessary condition to build up an O2-rich atmosphere, but it’s not sufficient. That’s because over geologic time, the O2 produced by biology is consumed by reactions with rocks and volcanic gases that come from the Earth’s O2-poor interior. So the amount of O2 in the atmosphere doesn’t just depend on biology. It depends on the solid Earth,” explains Anbar.
In their attempt to solve the mystery, Anbar and his researchers will integrate models of atmospheric chemistry, records of Earth's surface O2 history developed from inorganic and organic geochemical proxies, laboratory calibrations of these proxies, geochemical analyses of samples from the lithosphere and mantle, seismic reconstructions of Earth's interior structure, geodynamic models of mantle mixing and evolution, thermodynamic calculations and findings from mineral physics experiments.
In short, this isn’t a one-man job.
Earth system dynamics and its role in human evolution in Africa
Understanding the relationship between Earth history and human evolution is an enduring challenge of broad scientific and public interest. Scientists studying the effect of ancient climate change and human evolution have had to depend on local, but incomplete terrestrial records, or analysis of deep ocean cores collected a considerable distance from where major hominin fossils – the ancient remains of human ancestors – have actually been found.
The Hominin Sites and Paleolakes Drilling Project (HSPDP), funded in part by the NSF-FESD award, comprises a multinational research effort with researchers led by Andrew Cohen of the University of Arizona, ASU and 22 other institutions that will help scientists to better understand the dynamics that link climatic and evolutionary histories. The total continuing grant award will be nearly $4.8 million, with $1.2 million as ASU’s portion of the funding.
After over eight years of planning, five sites have been identified in Kenya and Ethiopia that are in close proximity and geologically and chronologically related to time periods critical to human evolution over the last four million years. Two of the Kenyan sites were successfully drilled in the summer of 2013 with funding from other sources.
“Correlations between environmental change and human evolutionary history have often been made with very broad strokes and assume that global climate changes affected all of eastern Africa and in similar ways,” said Campisano, scientific project manager for the HSPDP. “Obtaining these high-resolution, high-sensitivity records documenting when and how environmental fluctuations impacted the landscapes where human ancestors lived is the necessary first step to test a variety of current hypotheses of human evolution.”
Campisano, Reed and Arrowsmith will lead the scientific team in the Northern Awash River Valley in the Afar region of Ethiopia, close to where the 3.2 million year old fossil skeleton, Australopithecus afarensis, popularly known as “Lucy,” was discovered in 1974 by Institute of Human Origins founding director Don Johanson. They will assess the environmental record in the lake system that was active adjacent to the riverine landscape in which the animals lived.
Ariel Anbar, Anbar@asu.edu
Chris Campisano, Campisano@asu.edu