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Biology 103
2001 First Web Report
On Serendip

Man's Evolution

Caitlin O'Keefe

The history of the world and all its living organisms has been a mystery to mankind for hundreds of years. The questions of origin and time have plagued man's quest for knowledge. Only recently have people been able to uncover answers to the past due to great advancements in our own thinking power and research abilities. Perhaps one of the most compelling questions that man has encountered is the origin of his own specie. Where did we come from?

This very same question was asked by profound scientists of the nineteenth century. Sir Charles Lyell, a British geologist, was one of the first persons ever to study the history of living organisms by means of researching fossils in rock layers. Lyell hypothesized that plants and animals did not change at all over time, but merely stayed the same until the species eventually died out. It wasn't until Charles Darwin published his Origin of Species that Lyell's theory was replaced. Darwin proposed that all living organisms evolved over time, with certain species more able to adapt to changing environments. In 1871, Darwin furthered this argument to the evolution of mankind in his book The Descent of Man. He theorized that mankind evolved from a sort of primitive ape specie that survived in a lush, green climate. (3) But it wasn't until the twentieth century that there was physical evidence to support this theory. In the Eastern part of Africa, centering round the present-day country of Ethiopia, scientists of the twentieth century have unearthed hundreds of hominid bone fossils dating back almost five million years when the continent of Africa became a much drier environment, allowing for some species of primitive apes to adapt to the change in climate. (1) And they are these apes that are the ancestors of the primates and humans that still exist millions of years later.

The first hominid species, Ardipithecus ramidus, is suspected to have lived about 4.4 million years ago. And approximately 4.2  3.9 million years ago, the specie Australopithecus anamensis existed on earth, though concrete evidence to describe these two species is sparse.  But in 1974, paleontologist Donald C. Johanson discovered in Hadar, Ethiopia the fossil remains of a female hominid dating back 3.2 million years. The bones of Lucy seem to provide evidence that hominids of that time period, called Australopithecus afarensis, had a bone structure that allowed them to walk upright. Scientists also suspect that a volcanic eruption in Tanzania covered the Eastern part of Africa in ash, which then turned to a cement-like layer of sediment after a heavy rain. Footprints of two hominid species were uncovered in the sediment in 1978 by Mary Leakey. After studying the prints and various foot bones that were discovered, which date back to Lucy's time, it is apparent that the ancestors of man were first characterized by a divergent big toe; they no longer walked on four legs, but became bipedal. Though Lucy, and most likely others of her kind, had similar skeletal structures to those of our own specie, her bones show that she was much shorter than modern humans, reaching a height of only four feet. She also had much longer arms, thus giving her the ability to climb trees as a defense mechanism. (1)

Following Lucy's specie, the Australopithecus africanus and Australopithecus aethiopicus species roamed the earth for about one and a half million years, feeding mostly on nuts, seeds, fruit, and tubers. About 2.3 million years ago, another specie evolved: Australopithecus boisei. Found in East Africa, this specie had a much larger bone structure and a flatter face than the A. africanus, and its skull was far more developed for chewing harder foods. (4) The Australopithecus robustus found in South Africa evolved 2  1.2 million years ago and is differentiated from previous species by the introduction of meat into its diet. This characteristic is expanded in the specie Homo habilis that inhabited East Africa approximately 1.8 million years ago. It is in this specie that the use of stone tools is first detected. Long arms and small bodies are still apparent in the bone structure, yet there have been so many variations of this specie that some scientists speculate the H. habilis specie is more accurately divided into two species, the other being named Homo rudolfensis. (1) >From 300,000 to 1.8 million years ago, a species called Homo erectus originated in Africa. It is the H. erectus that largely resembles man, as we know it. An increase in brain size, a receding forehead, and a thick skull are all characteristic to this specie. Also, body size is quite similar to that of modern man. And it is this specie that began to disperse across the world, beginning in Africa and later spreading across Europe and Asia. It is apparent that the H. erectus was able to sustain the climates of both warm savannas and cold, temperate, deciduous forests. (2) The Homo neanderthalnesis was a species that existed about 150,000  30,000 years ago, but there is debate about the connection between the H. neanderthalnesis specie and modern human beings. Though the specie was known to practice burial customs and use stone tools, the physical structure between the two species leaves room for discrepancy in terms of lineage and descent to modern species. The mouths of this previous specie are projected above the chin, and the brow protrudes from a low, long skull. (2) Finally, we come to the modern day specie of Homo sapiens. H. sapiens evolved about 100,000 years ago and are recognizable as our own kind. They arrived in Australia 60,000 years ago and in North and South America approximately 20,000 years ago. They have a generalized diet and are able to survive in many environments. The structure of the specie is robust, yet gracile. Rounder, larger skulls with smaller teeth and jaws are characteristic of the H. sapiens. And it is among this modern specie where a tremendous amount of advancement of culture takes place up to the point of present human life. (1)

Mankind has been evolving for millions of years. From primitive apes to advanced cultural beings, we have reached a point in our existence where we are able to question the origin of our species and the process of our development. It is because of this advancement and the great scientific thinkers of the modern world that we have been able to uncover some of the mystery of our kind that lies deep beneath the sands of time.

WWW Sources

1)Becoming Human. ,

2)The Evolution of Man. ,

3)Human Prehistory: An Exhibition. ,

4)The Smithsonian Institution Human Origins Program: In Search of What Makes Us Human. ,




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