The two hominin traits that stood out to me and can inform us about modern human biology is bipedalism and the changing of teeth size. Both of these features explain how humans work today. First, bipedalism is the form of locomotion using two limbs. Chimpanzees, monkeys, gorillas, etc., use all four of their limbs to move and transport themselves. However, as evolution continued, humans began to use only our two feet. However, the lecture talks about how we still see chimpanzees at the zoo stand up on two legs occasionally. Furthermore, the placement of the foramen magnum shows when the bipedal begins. When the foramen magnum is located underneath the skull, it suggests that the body is underneath the skull. Therefore, with the foramen magnum underneath the skull, rather than behind the skull like a quadrupedal, it suggests bipedalism. The placement of the foramen magnum is the earliest sign of bipedalism. Then, the sizes of toes differing can lead to the idea of bipedalism as well. Here, the abductable big toe has disappeared. The big toe is now in line with the other toes, which is similar to us. Moreover, we begin to see features of the pelvis and legs. All of these features suggest full-time bipedalism. Lastly, the fossil AL 288-1, “Lucy”, shows a mix of primate and human features. Lucy contains the form of human-like bipedalism, but also shows features of a primitive face with an ape-sized brain.
The second hominin is the changing of teeth size. Our teeth size has changed drastically throughout evolution. First, the difference between front teeth and back teeth with the species changed throughout evolution. Primitive ape-like features consist of large canines, where humans do not. The Ardipithecus contains more human-like factors than the other species. The Ardipithecus teeth show that the teeth are moving from an ape-like form to a human-like form. Next, the Australopithecus garhi have features similar to the genus homo. The teeth on the Australopithecus garhi and genus homo have large front teeth and big back teeth. However, their back teeth aren’t as big as the front teeth. These teeth patterns also begin to look more like us. In addition, the Paranthropus, or robust australopithecines, had specialized set of teeth used for chewing hard seeds and nuts. For the Paranthropus, the incisors and canines are very small. However, their molars and pre-molars are massive. In fact, their molars and pre-molars are about twice the sizes of ours today. For this, if your trying to grind hard foods like nuts and seeds, you don’t use your front teeth often. This is why the front teeth became smaller for the Paranthropus and made additional room for the very large back teeth that are good for crushing and grinding. Humans now no longer need big front canines to stab and bite. Nor do humans need large back molars to grind and crush hard nuts and seeds. We now have tools to help us with these tasks that old species dealt with. Therefore, the traits of teeth show how the species have changed throughout evolution.
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Hey Emily!
Just wanted to start off by saying that i think you did a great job at really going into depth about the two traits of teeth size and bipedalism! When i was watching the lectures this week, i found bipedalism to be super important, but i did not see the change in teeth size as important, but after reading this post, you have really changed my mind about it! The way you seperated and went over the sharp front teeth and then the large back teeth and what their purpose was and then applied it to the evolution of humans and how are teeth are based on our diet was really cool! Also you pointing out the importance of the foramen magnum can not be overstated! great job!
Hey Emily! I also found the bipedal trait to be particularly interesting during this past week. In the lecture, in order to give a better understanding about chimps using their two legs occasionally today, I liked how it compared the struggle to how a dog would react trying to stand on two legs. I understand that it is uncomfortable for chimps and they can only do it for so long, so this is why they don’t use their two legs strictly when they move, although they can definitely use it to their advantage. Along with the foramen magnum underneath the skull, these findings in prehistoric bones have a huge impact in finding where an individual belonged during prime times of evolution. I, too, discussed dental anatomy in my blog post, and I mainly loved learning about how the differences in diet among different groups affected teeth size.