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Answering Questions About Proconsul

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© W. Harcourt-Smith


Last year, William Harcourt-Smith, an assistant professor at Lehman College and a research associate in the Museum’s Division of Paleontology, blogged for the Museum about his research on the Kenyan island of Rusinga. Harcourt-Smith co-directs a paleontological field project on the island, which is best known as the site of the discovery of the first fossils of Proconsul, an early ape. Below is an excerpt of a longer story that Harcourt-Smith wrote for the Summer 2012 issue of Rotunda, the Member magazine.

One of the reasons we chose to revive work on the island is the outstanding fossil preservation it offers. Rusinga and the neighboring island of Mfangano are treasure chests of fossilized remains from the time Proconsul lived. The reasons for this are largely due to the distinct geology of the region. At the time Proconsul was flourishing, the nearby volcano of Kisingiri was highly active, and spewed out ash and pyroclastic lava flows at regular intervals over millions of years. This resulted in many plants and animal remains becoming covered and exquisitely preserved, in part due to the chemistry of the volcanic ashes. Of course you have to add to that a good dose of old-fashioned luck. On Rusinga, the fossil-bearing layers of just the right date are exposed at this particular moment in time.

Our approach has been deliberately multidisciplinary. We have geologists, paleobotanists, soil chemistry experts, radiometric dating specialists, and even the world’s only expert on fossil aardvarks. To date we have found over 4,000 identifiable fossils from a multitude of sites on the islands, and they promise to provide us with an extraordinary window into the time when Proconsul thrived. We have beautifully preserved remains of fossil leaves, wood, and seeds. There are abundant insect remains, including the tiny chambered nests of bees. On the larger scale, we have the immense long bones from extinct relatives of elephants called Deinotheres and from strange, knuckle-walking creatures called Chalicotheres. And, of course, we have plenty of Proconsul.

All these finds are very important in their own right, but perhaps one of the most relevant things we have been doing is to very precisely log every specimen we find at each locality using the latest technologies, such as differential GPS and high-resolution satellite imagery. Combined with precise microstratigraphic work and archaeological excavation techniques at a number of fossil-bearing sites, we are attaining an incredibly detailed glimpse into what the past depositional environment was like.

In paleontology, teams often prospect for fossils simply by walking across promising areas until they find something; if they do, it then gets methodically excavated out, but there is little in the way of context. I infinitely prefer this type of discovery to sitting in a hole all day with a dental pick, but in fact, that kind of painstaking work can reap highly significant results. Find a distinct type of plant at the same exact layer as aProconsul tooth, and you can say something definitive about the environment Proconsul lived in. Find them scattered on the surface, and there is far less certainty.

We are still in the midst of processing and analyzing our data, but there are some exciting results coming out of the project. It’s clear, for instance, that there were more than one species of Proconsul living at the same time and place on Rusinga. There is no modern correlate to this among apes, and we are currently trying to work out how the ancient environment would have supported them both. We are finding an abundance of new plant remains that will be hugely important for understanding the precise type of environment Proconsul lived in, and just recently we have gotten our first glimpse of environmental shifts over the 3 million or so years’ worth of deposits we have on the islands. How the earliest apes like Proconsul might have dealt with this remains a fascinating prospect.

A Science Bulletin documentary that followed Harcourt-Smith’s team into the field in 2011 will be on view later this year in the Spitzer Hall of Human Origins or online at http://www.amnh.org/explore/science-bulletins. A longer version of this story appears in the Summer 2012 issue of Rotunda, the Member magazine.

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