Humans

Cristela Aguilar

Anthropology 161

July 21,2005

Final Exam

4. The word hominid refers to members of the family of humans. It includes all species from our human ancestors and also all living apes, such as the Hominoidea.

The hominid fossil record will not be complete for a long while, but there is enough evidence for researchers to give us good idea about the history of humans. There are a number of fossils that have been found throughout the researchers journeys. One of them is called Ardipithecus ramidus. It is the oldest known hominid species, found in Aramis, Ethiopia in 1994 by Tim White. Most remains are skull fragments. Indirect evidence suggests that it was possibly bipedal, and that some individuals were about 4'0 tall. The teeth appear to be more apelike than any other hominid. Another fossil is the Australopithecus africanus which was found by Dr. Raymond Dart in 1925 in a limestone quarry in South Africa. Brain size ranged between 420 and 500 cc. Although the teeth and jaws of africanus are much larger than those of humans, they are far more similar to human teeth than to ape teeth. There are eight species named so far. There are two general categories for these species, "gracile" which is slightly built and "robust" which is heavier built.

Australopithecus afarensis is another fossil that existed between 3.18 million years ago. It was found in Hador, Ethiopia. A. Afarensis had an apelike face with a low forehead, a bony ridge over the eyes, a flat nose, and no chin. They had jaws that were sticking out with large back teeth. Their brain size was from about 400 to 500 cc. The skull is similar a chimpanzee, except for the more humanlike teeth. The canine teeth are much smaller than those of modern apes, but larger and more pointed than those of humans. Their pelvis and leg bones resemble those of modern man, and they were bipedal. Their bones show that they were physically very strong. Females were significantly smaller than males. Height varied between 3'6" and 5'0" and they weighed about 35-50lbs. Australopithecus robustus existed 1-2 million years ago. They had a similar body to that of africanus, but a much larger and more robust skull and teeth. It weighed about 75-200lbs and was about 3.5-4.5 feet tall. It has a big flat face with no forehead and large brow ridges. It has fairly small front teeth, but massive grinding teeth in the lower jaw. Most specimens have sagittal crests. Its diet would have been mostly coarse, tough food that needed a lot of chewing. The average brain size is about 530 cc and its capacity was from about 400-550ml.

Two other type of fossils found in the hominid specie are homo erectus and homo ergaster. Homo ergaster was found about two million years ago in Lake Turkana, in Northern Kenya. It was considered to be a specie with a large-body and large-brain. It has a high cranial vault, thin cranial bone and it doesn't have a sagittal keel. Now the homo erectus was also found in Kenya and lasted about 1.5 million years. They both have very similar aspects of their anatomy.

There are a number of fossils that have been discovered and some that are yet to be discovered that show physical evidence of the different types of hominids that exist and have existed in our world.

5. The fossil Homo ergaster was found about two million years ago in Lake Turkana, in Northern Kenya. It was considered to be a specie with a large-body and large-brain. This hominid species is believed to be a different geographical population of Homo erectus. Many aspects of Homo ergaster and Homo erectus anatomy are very similar. The main differences between them are that the Homo ergaster has a higher cranial vault, thinner cranial bone, the absence of sagittal keel, and certain cranial base characteristics that homo erectus doesn't have. There is one unique characteristic between the early Homo and ergaster/erectus which is the increased brain size. Some features that differ mainly in the homo erectus are they have a long, low cranium, they have the presence of brow ridges and a shortened face. They also have a nasal opening that makes researchers imply that this is the first appearance of the typical human external nose with the nostrils facing downward.

7. There are two different hypotheses that exist which try to explain where the Homo erectus first arose. There is the "Out of Africa" and the "Multiregional Hypothesis. The "Out of Africa" hypothesis was brought forward in 1987 by Allan Wilson. In this hypothesis it is believed that a single population in Africa led the change in homo erectus. Wilson proved that all humans developed from a single female about 200,000 years ago. The Multiregional Hypothesis believes one million years ago the homo erectus expanded through Asia and Europe and became the direct ancestor of the Homo sapiens. Researchers have debated on how, when and where modern humans originated. A study was done in Cambridge University where DNA was studied to help gain evidence to these hypothesis. The DNA that was studied for the research came from mitochondria and cellular organelles that convert food into a form of energy that that rest of the cell can use.

All of this research made Wilson conclude the region of origin for modern humans which was Africa and he estimated how long ago it happened which was about 200,000 years ago. He believed that the female who contributed her mitochondrial DNA to the world was a member of a population of an estimated 10,000 individuals. Also, he