Over the past week, as we went through the various hominins and species that are a part of the evolutionary tree, we learned about a few specific traits regarding each of the species we learned about. Some of these hominin traits include bipedalism, type and size of the sets of teeth, arm length, and brain size. The main focus was on the fact that all hominins were primarily/mostly bipedal, which this evolved trait led to many of the others humans now possess.

Many of the early hominins, such as Sahelanthropus tchadensis, Orrorin tugenensis, and Ardipithecus, have not as many remaining bones, both crania and postcranial, however, some fragments and parts of the skeleton have been found. For the Sahelanthropus, no postcranial bones have been found, BUT, the anterior location of the foramen magnum suggests that this species may have been bipedal. Because this is one of the earliest hominins, at around 6 to 7 million years ago, this shows that around this time, one of the common ancestors between humans and chimpanzees had an evolved location of the foramen magnum. Depending on where this sits, we can tell whether a primate was bipedal or quadrupedal. Per the video on Ardi, Ardipithecus remain one of the clearer examples of early hominins being bipedal, although they could walk but probably not run (opposable big toe for stability not propelling foot). Over time, later and later hominins were able to use their legs and their bipedalism to move quicker and probably for longer periods of time. Per the notes, “Lucy”, an A. afarensis, was likely fully bipedal and able to live in a variety of environments. It is clear that becoming bipedal has had a large impact on human evolution because, positively, we are able to reach fruit and other objects, run, go longer distances (because it burns less calories), etc., however, in the second reading, birth has become more difficult and fatal, we have severe back problems, and so on. So, understanding how hominins were bipedal help us explain not only these problems, but also why we have become bipedal and why quadrupedals like chimpanzees and gorillas, have remained as such. Understanding the teeth of hominins has also helped because chimpanzees and other hominids have long and sharp incisors for attacking, while ours are for biting food. Over time, our molars have become smaller among other teeth, but more so for our diets. Ardipithecus, whose primitive traits included relatively large canines, which were more like incisors in structure, show that our teeth have evolved so that they can become more fitted for our lives. Even robust forms, like Paranthropus, were characterized by their ability to chew, so much so that their teeth, mandible, and other facial structures were useful towards eating and chewing. A. garhi even had teeth that looked much more like the genus Homo, suggesting that they are much more related to humans than previous species. Looking at the teeth of previous hominin species helps us understand why our teeth are the shape/length/size they are and why we use them for specific tasks. Lastly, arm length is interesting because of how it has changed. For the most part, prior to A. garhi, hominin arm length has been incredibly long, because for much of this time there was still activity in the trees and not solely on land like humans. As stated in the notes, a. garhi’s arm to leg length ratio resembles modern humans and helps us know why our arms are the length they are because they were initially “built” for tree use like other hominids but have shortened because we do not live in the trees in the same way “we” (other hominins) used to.

Being able to reconstruct human ancestors and their environments has proved incredibly useful for anthropology and understanding our past. We, for one, have been able to date when things occurred simply by comparing fossil locations in the strata and other types of dating. We also can understand how we have evolved, what we looked like in the past, how we have used certain bones and for what, what kinds of diets they had, and why we have evolved. If certain characteristics were gone from the next branching species or a specific species relatively quickly went extinct, we can learn from that to better understand those hominins and ourselves.