Macroevolution of Hominids Essay

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Evolutionary scientists believe that all living things are as a result of various evolutions occurring due to climatically and environmental changes over a long period of time. Studies show that the hominid is the word used to refer to human family which consist of human and ape ancestors (Niles, 2005). There are various studies touching on the macroevolution of hominids and though fragmented there is tangible evidence to prove evolution of human history. This paper is written to critically analyze the concept of macroevolution of Hominids. Hominid species in this paper will be recorded in terms of appearance in the fossil records:

Sahelanthropus tehadensis: This species was discovered in 2002 from fossils found in Chad which is a country in Central Africa (Cameron, 2004). This species is deemed as one of the oldest fossils in the world since its existence dates 6 to 7 million years ago. The features of the fossils showed fragmented lower jaws and teeth, the brain was very small of approximately 350cc (Haviland, 2003). This species also had very small canine teeth and from its structure it can be argued that it came from the chimpanzee and human ancestors (Cameron, 2004).

Orrorin tugensis: This species was discovered in western Kenya a country in the African continent in 2001 (Haviland, 2003). The fossils include fragmentary arm, teeth, thigh bones which date back to 6 million years old and its structure was slightly bigger that of Sahelanthropus tehadensis (Haviland, 2003). There are many controversies surrounding this species since some believe it was a human ancestor while others think it was a chimpanzee ancestor. Ardipithecus ramidus: This species was discovered in 1994 and its origin dates back to 4. 4 million years ago.

Indirect evidence points that the species was bipedal with a height of about 4 inches tall (Jurmain, Kilgore, Trevathan, Nelson, 2003). The teeth seemed to resemble those of earlier apes with one baby tooth resembling that of a chimpanzee tooth (Cameron, 2004). Most probably the species lived in the forest and that explains why most hominids were bipedal. Australophithecus anamensis: This species were discovered in 1995 with most of the fossils being discovered in Kenya (Jurmain, Kilgore, Trevathan, Nelson, 2003). The teeth and jaws were very similar to those of older fossils.

This species is subject to contradictions between evolutionary scientists. Australopithecus afarensis: This species existed between 3. 9 and 3. 0 million years ago and it had an ape like face, protruding jaws and large black teeth (Larsen, Matter, Gebo, 1998). The brain size was between 375 to 550 cc and the teeth are more human like with disparities from both chimpanzees and those of humans (Christopher, 2004). The fossil bones available show that they were very strong although females are smaller than men with differences ranging from 3. 6 inches to 5 inches.

Kenyanthropus platyops: This species was found out in Kenya with varied mixed features from the early apes. The fossil is aged about 3. 5 million years old and the skull is the same as that Australopithecus afarensis and Austrolopithecus africanus (Lemonick, Dorfman, 2001). The species has a large flat face and small teeth. Australopithecus africanus: This species existed 3 to 3 million years ago and has a larger brain ranging 420 and 500 cc (Larsen, Matter, Gebo, 1998). The brain is larger than that of the chimp and the teeth are much larger than those of the humans.

Australopithecus garli: This species were discovered in 1999 and they have larger size of teeth and have primitive skull morphology (Haviland, 2003). Only a partial skull was discovered so no much conclusions were made. Australopithecus aethiopicus: this species existed between 2. 6 and 2. 3 million years ago. The species had a brain size of 410cc and primitive limbs like big face, jaws and also had the largest sagital crest in any known hominid (Larsen, Matter, Gebo, 1998). Australopithecus boises (was Zinjanthropus boisei): This species had a learger skull and teeth and its existence dates back to 2 to 1.

5 million years ago. It had a brain size of about 530 cc and the bones excavated with the species may have been used as digging tools (Haviland, 2003). Their structure leads scientists to believe that they are human ancestors. Homo habilis: This species is called the handy man more especially with the evidence tools found with his remains. The species existed around 2. 4 and 1. 5 million years ago and the black teeth a larger than those of the modern man and a brain size of 650 cc with specialized speech areas (Larsen, Matter, Gebo, 1998). Homo habilis was about 5 inches tall and weighed 45 kgs.

Homo georgicus: This species was discovered in Georgia in Dnanisi and the fossil is about 1. 8 million years old. The brain size varies between 600 and 780 cc with an estimated height of about 411 (Jurmain, Kilgore, Trevathan, Nelson, 2003). Homo erectus: This species existed between 1. 8 million years and 300, 000 years ago. This species has protruding jaws, long low skull, no chin and brain size between 750cc to 1225cc (Christopher, 2004). The skeleton showed that the species was more affiliated to modern man with an upright walking gait.

Other studies show that the Homo habilis may have used fire and stone in advanced manner compared to previous Stone Age species. Home sapiens (archaic): This species appeared 500, 000 years ago and is directly affiliated to the modern human beings and the brain size is larger than that of the Homo erectus: 1200 cc (Cameron, 2004). Homo sapiens neanderthalensis: this more modern man like species existed 230,000 and 30,000 years ago (Christopher, 2004). The brain size is bigger about 1450cc with a marked buldge at the back of its skull, the chin is weak and has a height of about 56 inches (Jurmain, Kilgore, Trevathan, Nelson, 2003).

The bone structure is thick and strong depicting powerful muscles. The fossils were found with tools and weapons showing an organized form of living. Homo Floresiensis: This species is a dwarf form of Homo erectus, used stone tools and fire and hunted dwarf elephants found in Indonesian Island where it was discovered in 2003 (Jurmain, Kilgore, Trevathan, Nelson, 2003). The adult female was about 1 meter tall and the brain size was 417 cc. Homo sapiens sapiens (modern): Modern Homo sapiens first appeared about 195, 000 years ago.

Modern human beings have a brain size of 1350 cc, rised forehead, small eyebrow ridges (Niles, 2005). The species used improved shapes of bone tools, had clothing, and practiced sculpting through decorating tools, ivory, making carvings of humans and animals, musical instruments and clay figures (Niles, 2005). The teeth f this species is 10% more robust that those of modern human beings. Below is a time line of the macroevolution of hominids Sahelanthropus tchadensis Orrorin tugenensis Ardipithecus ramidus Australopithecus anamensis Australopithecus afarensis

Kenyanthropus platyops Australopithecus africanus Australopithecus garhi Australopithecus aethiopicus Australopithecus boisei Homo habilis Homo georgicus Homo erectus Homo antecessor Homo neanderthalensis Homo floresiensis Homo sapiens sapiens Reference list Cameron, D. W. (2004). Bones, Stones, and Molecules: Out of Africa and Human Origins. Burlington, MA : Elsevier Academic Press. Christopher S. (2004). The Human Story: Our Evolution from Prehistoric Ancestors to Today. Washington, D. C. : National Geographic. Haviland WA. (2003). Evolutionary forces.

Human Evolution and Prehistory. 6thed. Belmont, CA: Wadsworth/Thomson Learning. p. 74-80 Jurmain R, Kilgore L, Trevathan W, Nelson H. (2003). Chapter 1: The development ofevolutionary theory. Introduction to Physical Anthropology. 9thed. Belmont, CA:Wadsworth/Thomson Learning. Larsen, CS, Matter RM, Gebo DL. (1998). Human Origins: The Fossil Record. 3rd Edition. Prospect Heights, Illinois: Waveland Press, Inc. Lemonick MD, Dorfman A. (2001). One giant step for mankind. Time 158(3):54-61. Niles E. (2005). Darwin: Discovering the Tree of Life. New York: W. W. Norton & Company.

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