The moment we have all been waiting for has arrived, the human evolution module. For the module, Dr. Matthew Borths from the University of Ohio joins us to tell the story of our own evolutionary origins. Dr. Borths studies changes in African ecosystems, particularly as they relate to ape evolution, throughout the Miocene. He was also the graduate teaching assistant for the Origins field school in spring 2013!
To begin the story of human origins, we must first start at the evolution of primates, the order in which we belong to. Primates, in general, are characterized by a suite of features including larger brains, forward facing eyes, shorter snouts, long grasping fingers and toes and an opposable big toe.
The first true primates existed over 50 million years ago during a period of time called the Eocene. These primates featured much more primitive characteristics than what we see today in us and modern apes. For example, they lacked complete closure behind the eye (postorbital closure), a fused mandible, and an ear canal, and featured both an extra tooth and a tail. However, as the climate began a period of warming late in the Oligocene (time period between 34Ma-23Ma), the first apes appeared. One of these early apes is called Proconsul, which is dated to 20Ma. Proconsul, meaning “before Consul” was found in 1909 at Rusinga Island, Kenya and was distinctive in its ape like characters. In fact, it was actually named after Consul, a chimpanzee in the London Zoo. This animal lacked a tail, which is a feature that is shared by all apes. However, Proconsul and other early apes appear to be arboreal quadrupeds (meaning they walk on all fours in the trees), which is a way of locomotion that is lost in all modern apes. However, this fossil can give us insight into the features of our own last common ancestors with other apes.
However, before we can start talking about how our lineage evolved from our last common ancestor with chimpanzees, it is vital that we understand our own anatomy so we can track how it has changed over time. For this students headed into the lab to review human anatomy.
Knowing human osteology is crucial to the understanding of human evolution because the position and shape of our bones determines the way in which we function. Even though the hominin fossil record is fragmentary and far from complete, we can make educated inferences from the features on the fossils we have found about how different traits have changed throughout time to make us who we are. For example, much of our fossil record is comprised of teeth. Just from looking at how size and shape of the teeth have changed over time, we can infer how diet has corresponded to these changes.
After the intensive osteology training, students took to the field in areas where hominins have been found before. While we did not find any ancient humans, the students were able to stop by a hominin footprint site right here in Ileret on our way out to the field. This footprint site is dated to be 1.5 million years old and was likely made by a Homo erectus (a primitive human). Also, from the shape of the footprints, it has been hypothesized that this ancient hominin essentially had a modern human bipedal walking gait.
While no hominins were found on our field outings, we did have many other interesting discoveries.
The students are excited to learn about our origins in a place with such a rich history of hominin discoveries. Stay tuned to learn about how phylogeny, which portrays the evolutionary relationships between species, is constructed and how the students applied this knowledge to our own evolution!
Students in the Spotlight: Maria Mueller, Leah Neiman, and Izzy Brown