August 24, 2009

There and Back Again

Professor of Paleoanthropology at Lehman College and Research Associate in Paleontology at the American Museum of Natural History

Once again, I turn the blog over to CUNY grad student Julia Zichello –WHS |

We were kneeling on the ground at Kiahera, brushing and picking through the loose earth as the heat quietly drowned our thoughts. I decided that I just needed to sit down for a second. So I sat and swept my hand along the sloping hill and an astragalus (foot bone that belonged to a creodont, an extinct carnivore-like mammal) popped out of the ground with a little joyous flip. Well, hello! I thought, where have you been all of your life? It was under an extraordinarily thin layer of sediment and had I not brushed it away, it may have just continued to sit there unmoved, and I may have too.

Now I can reflect on what was both an intellectually enriching and just purely lovely and astonishing trip to Rusinga Island, Kenya. I have been thinking about all the evolutionary connections that the new data and experiences have elucidated. One is, well, what does an 18 million year old creodont astragalus have to do with ape evolution? And how do we knit the diverse and often fragmentary fossil data together into a complex and informative picture of hominid evolution?

We took the fossils we had collected in the field each day back to camp. Then, in a very beautiful losing race with the sun to the horizon, a few people worked on identifying each fragment. It was a puzzle. First, what region of the skeleton is it from and secondarily, to what taxa can we assign it to. The most mysterious pieces were twirled and twirled and passed around liberally. Wild and sharp opinions flew.

If the goal is to understand how environmental shifts have impacted morphological adaptation, it’s advantageous to focus on more than one extinct species, genus or even order. Especially if the fossils of other non-primate fauna practically throw themselves at you, like at Rusinga. We collected fossils of anthracotheres, chalicotheres, rodents, hyraxes, elephants, rhinos and even arthropods. There are three types of information that can be gleaned from each fossil: function, phylogeny and taphonomy—or, how did this animal move, what is it related to and what happened to its remains from the time of its death until now. Ideally, if all three are known from several taxa they can provide independent lines of evidence that converge on the common goal of environmental reconstruction. Then, as fossils and observations accumulate, we move more accurately and intriguingly closer to knowing more of the evolutionary story.

We returned to the Nairobi National Museum with bags and bags of new material. We were tanned, tired and continuing to catalog. The same fossils seemed different in the museum than they had in the field. The sun wasn’t in my eyes and they were data now.