The content for this week differed from previous weeks in that we focused mostly on the lineage of modern humans and the steps of evolution that lead us to what we define ourselves as. It is important to note that these evolutionary changes occurred over several millions of years and happened at various rates. The differences from us and our ancestors have to do with both physical and mental traits that can be used to distinguish specific points of evolution and progress towards our current state.

The first change that I will discuss is the evolution of bipedalism. This is described as walking upright on two feet, instead of walking on all four limbs as most apes do. This marked an important evolutionary change because it allowed for the early hominids to travel farther distances efficiently. This change was first seen approximately 6 to 7 million years ago in the species, Sahelanthropus tchadensis. This was seen in an individual skull and analysis of a feature on the skull lead anthropologists to the belief that this is the earliest example of bipedalism. The foramen magnum is an opening in the skull that serves as the point where the spinal cord connects to the brain. The placement of the foramen magnum offers insight on the pattern of walking for animals. If the foramen magnum is placed behind the skull it insinuates that the animal walks on four legs, however if the foramen magnum is below the skull, that is a feature seen in bipedals. This example of a foramen magnum seen below the skull was first seen in the S. tchadensis and marks the earliest example of bipedalism.

A second evolutionary change occurred in the species Australopithecus garhi. Prior to this, there was a group of Australopithecines that were categorized as robust. This was due to their chewing habits which involved crunching down hard seeds. Due to this, they had small frontal teeth and very large molars with strong jaw muscles. This aided in the breakdown of tough materials. In the A. garhi, the front teeth became larger and the premolars became similarly shaped to what we see in the “homo” species. Another change that occurred in this species was the shift towards longer legs and shorter arms, which makes them more suited for bipedal movement. This signifies the distancing from being part terrestrial and part arboreal to being mainly terrestrial like humans are today.

There are many features that have evolved and allow us to distinguish ourselves as homo sapiens. With the help of fossils and dating technology we are able to obtain an accurate estimate of when evolution changes may have occurred. Something I found interesting was being able to recreate the environment which these hominids lived in to learn about how the environment may have shaped them to evolve in a certain way. Some fossils are preserved better than others and this leads us to know more about this species. It would be interesting to know what other species we have not found fossils of and how they may have contributed to our evolution.