Zoey RentzBiology LectureBrief Human EvolutionHominoids, a superfamily classification that includes all apes and humans. Hominoids are then separated into size groups. The family classification of hominids, includes hominoids with a large body (orangutans, gorillas, bonobos, chimpanzees, and humans). Hominids are then separated into three subfamilies: Pongines (orangutans), Gorillines (gorillas), and Hominines (bonobos, chimpanzees, and humans). Hominines, are then broken into two tribes: Panins (bonobos and chimpanzees) and Hominins. Hominins are a tribe of bipedal hominoids that include humans.It is important to understand the lineage of our primate ancestors because many ofour behaviors are shared with primates especially in relation to how early hominins lived.The earliest hominin, named Sahelanthropus tchadensis, was dated approximately 7mya (million years ago) and found at the Toros Menalla site in Central Africa. Hominid fossilsfound only in Africa show that over the next 5mya hominins were restricted to Africa. Primates and hominids are similar in the respect of living in restricted areas and survivingon the resources readily available.Around two million years ago hominins had a change in behavior and expanded from Africa into other areas of the Old World. Why didn’t the hominins leave Africa earlier? I think the answer is as simple as why wont you get up and walk thousands of miles away from everything you know right now? Once some hominins left they began tolook and act differently than their earlier African forms. The hominins that left Africa are all part of the genus Homo. Fossil evidence from East Africa confirms that Homo erectus had a strong presence by 1.7 mya. These fossils found in Africa differ anatomically from the fossils of the species that left Africa and moved into Asia, the African fossils are therefore put into their own species, Homo ergaster. The African and Asian species represent geographical varieties within a single species. They differ anatomically based on their geographicallocation, but since they are closely related they are collectively called Homo erectus. The species Homo erectus lived during the Pleistocene epoch 1.8mya-5,000 kya (thousand years ago) during this time the ice age occurred and glaciers covered the Earth.Homo erectus fossils show clear evidence that this species began to adapt to their environments and shift, from an evolutionary standpoint, towards the human direction. The different populations of Homo erectus lived in different areas of the Old World and therefore, lived in different environments. Though they lived in separate populations theyare all still part of the same species and because of that they share common traits. In general Homo erectus adults showed an increase in height and weight resulting in a dramatically more robust individual. Adults weighed over 100 pounds and averaged aheight of 5 feet 6 inches. This made them taller than the Australopithecus yet shorter than Homo sapiens. Encephalization, is an increase in brain size relative to that animals total body size, is directly related to that animals level of intelligence. The cranial capacity of Homo erectus was twice the size of the Australopithecus cranial capacity. Showing a range in cranial capacity between 775 and 1225 cubic centimeters. Homo erectus brains were about 75% the size of the Homo sapien brain, showing they were less encephalized.The increase in brain and body size showed vast changes in the Homo erectus skull features. The skull is heavy with thick cranial bone. Above the eyes there are large brow ridges (supraorbital tori) and supraorbital sulcus (supraorbital foramen) that are depressions behind the brow ridges. The skulls do not have a large forehead since it (the skull) is longer and flatter. The occipital region of the skull is angled downwards, just below the nuchal torus. The nuchal torus projects from the back of the skull and it is where the neck muscles attach, these neck muscles hold the head up. The widest part of the skull is at the base below the ear opening, giving the skull apentagonal shape. This pentagonal shape is unique to the Homo erectus skull and is used as a diagnostic feature. The earlier and later skulls have a more vertical side with a maximum width above the ear openings. A sagittal crest is not present in Homo erectusskulls as it was in earlier species. The Homo erectus skull has a sagittal keel, a small ridge that runs along the sagittal suture from the front of the skull to the back. The sagittalkeel, browridges, and nuchal torus don't serve an obvious function but could just be support structures for the robust skull. Homo erectus also had two peculiar dental features: shovel shaped incisiors and taurodontism which is molars that have large pulp cavities. A very important anatomical feature that largely contributed to the expansion of this species throughout theOld World is their skeleton being more adapt to bipedalism, hence the name erectus meaning upright.Just after 2 mya a change occurred and a new pattern emerged in human evolution--traveling. This ancestor would have migrated from East Africa through the Middle East and into Eurasia. Once these individual populations settled in geographically separate areas they evolved to fit their environments. An example of this is seen with the Neanderthals, during the next glacial period the Neanderthals were isolated to Europe and they developed larger more robust skeletons. The Neanderthal and human genome have both been completed. Modern humans and Neanderthals are 99.84% identical, including a very important gene the FOXP2 gene, which is the “speech gene”. Neanderthals had the genes and the hardware to speak just as we do. However, it is unknown what language developments they may have had.Works CitedJurmain, Robert, Lynn Kilgore, and Wenda Trevathan. "Essentials of Physical Anthropology [Loose Leaf]." Essentials of Physical Anthropology: Robert Jurmain, Lynn Kilgore, Wenda Trevathan: 9781111838164: Amazon.com: Books. Wadsworth Cengage Learning, n.d. Web. 15 May
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