It’s my sixth trip to Ethiopia — the fifth for field work — and it’s good to be back. But, I do notice that each year I get older, my acclimation time is a bit longer!
It was 1997 when John Kappelman (UT Austin Anthropology) and Tab Rasmussen (Washington U. Anthropology) came to this very place to explore for the bones of human ancestors — BUT that was because a paper had been published back in 1985 stating the rocks here were only 8 million years old, or less. What they found were fossil bones of mammals that had to be much older — and with new dates we now know they are 20 million years older. In addition to finding these old mammal bones, they found many plant fossils. I was then invited to join the Chilga project (Chilga is the name of the “woreda” or administrative district) as its paleobotanist — and it’s been incredibly rewarding for me and my students.
We know from the work of Aaron Pan, who received his PhD in May 2006, that the forests occupying this region of northwest Ethiopia 28 million years ago were similar to those found in Central, West, and East Africa today. The eastern and western forests are currently separated by the East African Rift — which has varied vegetation including savanna, scrub, woodland, and montane forests. Some plant genera found separated today in the east and west, are represented by ancient, now extinct, relatives at Chilga (perhaps these are ancestral). Aaron also found that palms played a more significant role in forests then than they do today ??? Africa is unusually poor in palm species. The climate where the living relatives of the plants Aaron described is as wet or wetter than Chilga today, but has more rainfall during the winter months — Chilga has about 7 months of dry season today.
Juan Garcia Massini, an SMU graduate student, is working on finishing his PhD, in which he is describing the fine-scale physical and plant ecological variation that occurs on a landscape repeatedly disturbed by volcanic ash deposition. He has found that ferns and legume (bean family) play an important role as pioneer plants, and other interesting facts that will emerge as he publishes his work.
This year, Dan Danehy joins us to start a MS project focused on some aspect of paleobotany at Chilga.
I have been collaborating with students and our colleague in the Dept. of Earth Sciences at SMU, Neil Tabor, who is studying the ancient soils and climate of this region. My own work deals with the estimation of past climate from the shape and size of fossil leaves — as well as fossil plant description, which I am becoming more intrigued by as we find more and more fruits and seeds that have not yet been studied.