blog 5

Significant evidence of bipedalism was first found in the bipedal leg structure of early hominin Orrorin tugenensis who lived between 6 and 5.8 mya. Later in early hominin Ardipithecus, the position of the foramen magnum in their brain structure and spinal cord shows greater evidence of their reliance on bipedalism for greater locomotion. In an even later homin Australopithecus afarensis, features of the pelvis and legs provide even greater evidence of the full use of bipedalism for locomotion. A well developed arch in the foot of this hominin species found in Laetoli footprints, also suggest greater bipedal characteristics similar to hominids. The dental anatomy of early hominins greatly resembles the dental anatomy of the later hominid. For example, early hominin Ardipithecus who lived between 5.8 and 4.4 mya, shows to have had teeth similar in shape to the later hominid such as; larger canine teeth that resemble the structure of incisors seen in hominids. A later species of the Ardipithecus referred to as Ardipithecus ramidus, was found to have derived smaller teeth such as canines which are more similar to the dental anatomy of hominids. In later hominins such as Australopithecus afarensis who lived between 3.9 and 2.9 mya, evidence of a greater reduction in the size of molars and canines increased the similarity between the dental anatomy of hominins and hominids. Lastly, the facial traits of early hominin Sahelanthropus tchadensis who lived between 6 and 7 mya, show commonalities of the smaller hominid like facial traits such as large brow ridges and a flat face. These hominin traits help our understanding of modern human biology by informing us of the physical traits inherited by hominids by early ancestral hominins and how these traits evolved over time to become more similar to those of hominids.


The diversification of late hominins due to the pressures of selection and environmental adaptation, caused early hominins split into two diverse groups consisting of robust and gracile forms.Robust forms such as Paranthropus, developed specialized chewing abilities as their dental anatomy derived smaller front teeth and larger molars. Robust hominin traits resemble human traits on a much smaller scale than their counterpart, gracile forms. Gracile forms such as Australopithecus are thought to be direct ancestors of humans because they developed many features that resemble humans, more so than robust hominins. Gracile hominin Australopithecus garhi derived human like features such as a less robust head, similar arm to leg ratio and dentition characterized by large front teeth and premolars shaped more human like. A later gracile hominin Australopithecus sedbia, derived features further linking gracile forms to humans including the reorganization of the frontal lobe, pelvic shape and features of their hands and feet. The split of later hominids into these two forms affected the path that human evolution by introducing greater variation in traits that became more similar to humans, as they evolved in order to adapt to their changing environments. Human traits seem to be linked more closely to gracile forms of hominins as hominin diversification granted these hominins with greater human like traits.


3 thoughts on “blog 5

  1. While the late australopithecines were similar to humans anatomically below the neck, their heads were significantly different from ours in several key features. Their adult brain size was about 1/3 that of people today. As a result, the widest part of the skull of these early hominins was below the brain case. For modern humans, it usually is in the temple region. Early hominin faces were large relative to the size of their brain cases. They had comparatively big molar teeth with thick enamel. By comparison, their front teeth were small. They had large jaws, and powerful jaw muscles. The size and shape of these muscles is indicated by flaring zygomatic arches click this icon to hear the preceding term pronounced, or cheek bones, behind which the major jaw muscles pass and the presence of a sagittal crest click this icon to hear the preceding term pronounced, which is a jaw muscle attachment ridge of bone on top of the skull in the robust species. In modern humans, the jaw muscles are much smaller and attach onto the skull in the temple region. From the side view, early hominin faces were concave or dish-shaped and projecting forward at the bottom due to their relatively small brain cases and huge teeth and jaws. In contrast, our teeth and jaws are relatively small, and our faces are nearly vertical.

  2. Hello, I first just wanted to say I felt you did a really good job of going through the beginning of bipedalism in the species’ that existed that were so similar to ours. It’s very interesting to me how much information we can get from the study of paleontology. The fact that we can know anything at all about a species that lived over 5 million years ago is mind-blowing. I thought it was especially interesting reading about the paranthropus species. Just from looking at their old teeth scientists were able to presume not just the kind of diet that these mammals lived off of, but what had caused them to change as well. I think all the different hominid branches caused by the pressures of selection and environmental adaption is one of the things that allowed for humans to be so unique and extraordinary.

  3. You did an extremely good job of taking us through the timeline of hominins. It’s so weird that we have fossil remains that date back centuries ago. These fossil remains has really allowed us to better understand how humans got here and learn more about other primates that we share common ancestors with. I really thought it was extremely interesting learning about these different hominin. It’s mind blowing to me that hominin, who look like apes, are able to walk around on two feet like humans. I wish they were still around today, I would love to see something like that. Overall I really enjoyed your post. It was extremely detailed and informative.

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