December 2007

Digging into Ethiopia’s botanical past

Team hopes to gain better understanding of area 28 million years ago

Prof. Bonnie Jacobs (left) and Prof. Neil Tabor (center) with some of the excavation team.

Why is it important to understand the evolution of Africa’s biomes (forests, woodlands, and savannas), the plant species that comprise these, and the climate history of the continent?

Because climate has no geographic boundaries. The behavior of African air masses and their interaction with oceanic circulation off the African coasts, impacts climate elsewhere in the world. This holds true now and for times in the past.

A team of researchers lead by Paleobotanist Bonnie Jacobs and Sedimentologist Neil Tabor of Southern Methodist University returned to northwestern Ethiopia in late December 2007 to spend almost a month collecting additional plant fossils and gaining a more thorough understanding of their geological context. (Read the team's blogs.)

In December 2006, the team collected more than 600 plant fossils, which are on loan for study in labs at SMU’s Department of Geological Sciences. All told, the team has documented more than 1,500 plant fossils, hundreds of vertebrate fossils and numerous examples of ancient soils. This year they widen their search to better understand the geology, landscape, plant and animal communities, and climate of Chilga, Ethiopia, 28 million years ago.

The project, which also is training Ethiopian students in geology and paleontology, is funded by a $300,000, three-year grant from the National Science Foundation. In this second year of the grant period, the team will collect from a fruit and seed deposit (to compare with that collected last year), sample leaves to provide information about insect plant-eaters, and explore for new fossil sites.

The project is expected to help us understand our current changing climate, by knowing about that of the past based upon plant fossils and ancient soils. Documenting past climate at low latitudes, including in Africa, helps us understand global climate change. In addition, the early origins of Africa’s flora are largely a mystery. What we know comes primarily from hypotheses generated by the modern distributions of plants rather than from the fossil record.

Angiosperms, ‘flowering plants’, make up nearly all the plants living in today’s tropical, subtropical, and temperate regions. In Africa, little is known about how they changed and adapted between their evolutionary origins about 130 million years ago and more recent times. Fossils from Chilga, Ethiopia, provide us with a unique and important view of the Earth's plant life 28 million years ago – filling a gap in our understanding of the evolution of today’s tropical floras.

The 2006 effort focused on, CH-3, which was known to produce both plant and vertebrate fossils. Until last year, only 92 plant specimens had been collected from CH-3 and these all came from the surface. Plant fossils picked up on the surface are usually bigger, less delicate specimens because they have been exposed to erosion and perhaps some movement from their original position in the sediment.

The researchers excavated into the hillside at CH-3, exposing the fossiliferous deposit and, after only eight days, collected 523 specimens - mainly fruits and seeds. Their finds included some things never seen before at Chilga – several flowers, some very tiny seeds, and a large fruit, all of which are still being studied.

This year’s team includes:

  • Bonnie Jacobs – SMU, Department of Earth Sciences
  • Neil Tabor – SMU, Department of Earth Sciences
  • Dan Danehy – Master’s Degree student, SMU, Department of Earth Sciences
  • Harvey Herr – Undergraduate, SMU, Department of Earth Sciences
  • John Kappelman – University of Texas at Austin, Department of Anthropology
  • Ellen Currano – Penn State University, Ph.D. student

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