STAGES OF HUMAN EVOLUTION |
| stages-of-human-evolution |
Objectives:
This article is based on Hominid evolution. Throughout the article, an emphasis will be on the importance of fossil evidence in our ancestors.
After reading this article, we will be able to :
understand the concept and various theories of human evolution on the earth surface.
learn about the genetic relationship between humans and our primates.
Identify major fossil groups: Australopithecus, Homo Habilis, Homo Erectus, Homo-Neanderthalensis, Homo sapiens and Homo sapiens sapiens.
Introduction
The concept of creation:
There are questions that have bothered mankind for ages such as from where did we come from, when did our ancestors appear on earth? There has been numerous answers to these questions.. But common to all early ideas was the concept of creation. It was almost universally accepted that the world and all its creations- plants, insects, birds, animals and human beings-were created at the same time by some supernatural being, call it God, or whatever.
No wonder, the idea of creation was deep-rooted in almost all religious faiths and humans were considered to be the supreme creation of god
. Science, however, looks at things differently. It tries to understand and observe facts on the basis of logical explanations and evidence wherever possible.
What is evolution?
Evolution is defined as the process by which different kinds of living organism developed from earlier forms.
In other word it would define as the development of dissimilarities between ancestral and descendant population.
In the process of evolution all living organism on this earth surface witnessed certain changes in their morphology through time.
The evolution of man can be studies through its morphology by comparative anatomy of fossils and also by the comparative biochemistry of the present day humans, apes and other primates.
The fossil record of the human history, although rudimentary, has been quite helpful in determining largely what we are seeking, namely a sound history and evolution of human species. This observation is obvious if one looks at the fossil history from early primates to the present man.
Theory of Human Evolution
Different theories have been given by different scholars, scientist, Anthropologist, religious teachers regarding the origin and evolution of man. During the 18th century, scholars grew increasingly interested in biological diversity and human origins.
Theory of creationism
Before the scientific discoveries of fossils records, in the theological world the commonly accepted explanation for the origin of species came from Genesis, the first book of the Bible, wherein it is stated that God had created all life during six days of creation and this is known as the theory of creationism.
Theory of Catastrophism
According to this theory, fires, floods and other catastrophes had destroyed ancient species. After each destructive event, God had created again new contemporary spices.
Theory of Transformism/Evolution
Theory of transformation/evolution is the alternative to creationism and catastrophism. Evolutionists believe that every species arise from others through a long and gradual process of transformation, or descent with modification. Charles Darwin became the best known of the evolutionists.
In 19th century, Charles Darwin put forward the idea that humans have evolved from apes, in his book The Descent of Man.
In the 20th century a numbers of fossils remains were discovered from different parts of globe. All those discoveries gives us a good ideas on the origin of human being. As per the paleontological study the primate fossil history dates back to 60 million years i.e. to Paleocene times.
In the line of hominid evolution the major fossil record was that of Dryopithecus. Dryopithecus belongs to the sub-family Dryopithecinae which included chimpanzees, gorillas and orangutans..
Trends in Human Evolution
The world‘s climate began to get cooler in five to ten million years ago, and the rain forests of Africa were replaced with savannas and open woodland. In these climatic changes evolved a new kind of hominoid of bipedal order. These new hominoids are classified as hominids-that is, of the human line. There are two major groups of hominids: the genus Homo and genus Australopithecus.
Australopithecines: The Earliest Hominins
The oldest known hominidae remains are classified as belonging to the genus Australopithecus and are found only in Africa. The first ever australopithecine fossil was found in 1924 at Taung, South Africa by famous anatomist Raymond Dart and the skull to be 2.8 million years old. Professor Raymond Dart coined the term Australopithecus Africanus.
Other Australopithecus Species (3-2 million years ago)
In 1938, a second kind of Australopithecus was unearthed in South Africa. Called Australopithecus robustus, it had massive teeth and jaws. In 1959, in East Africa, Mary Leakey discovered a third kind of Australopithecus called Australopithecus boisei Like the other australopithecines, Australopithecus Boisei was very old-almost 2 million years. In The skeleton and other similar fossils have been assigned the scientific name Australopithecus Afarensis (from the Afar Desert). In the subsequent years, three additional kinds of australopithecines have been reported.
Homo Habilis or the Handy man (Place-Olduvai Gorge,East Africa 1.8 Million years ago) |
| human evolution |
The first fragments of Homo Habilis fossils earthed by the British paleoanthropologist and son of Louis S.B. Leakey, Richard Leakey and his team around 1960, about the same time that Boisei fossils came up. But at that time they didn‘t really provide any clue to the creature they belonged to. It was only in April 1964 that it was announced that 1.8 million year old fragments belonged to a new genus with features resembling humans more than apes was discovered. At the suggestion of Raymond Dart it was named Homo Habilis, or handy man.
The name was quite appropriate as a large collection of primitive stone tools were also recovered at the same site, indicating that Homo Habilis was indeed quite adept at making tools.
The face of Homo Habilis was flatter than that of any of the Australopithecus species and its brain size was significantly larger-680 ml-although still only half as large as the average human brain today. So Homo Habilis must have been more intelligent than any of the earlier ape-like ancestors of man. But what is more significant is that the Habilis brain was not only bigger but also more complex than the brain of any of the Australopithecus species.
From the shape of the skull and the marks of its inner surface, brain specialist have identified a specific area in the Habilis brain similar to what is known as Barca‘s area in the human brain, which is essential for speech.
This means that, although Homo Habilis had a brain only half as big as the human brain, it probably had the capability of uttering a few simple ―words‖, but not much. The appearance of Homo Habilis marked a quantum jump in the human evaluation process. Australopithecus Robustus and Australopithecus boisei which came before it were mare apelike, living an exceedingly primitive life, without articulate speech, with poor tools and weapons and probably surviving on a meatless diet. In which heralded not only the beginning of speech, but also the all important advantage of stone tools.
From the kind of stone tools found at Habilis sites one thing became clear, Homo Habilis was intelligent enough to gather the right kind of stone for making tools from places as far as 10 to 15 Km away and then shape them carefully in to various forms.
From the way the tools were shaped by hand by flaking, one can tell that the first human like tool makers were right handed. They were possibly our earliest ancestors known to eat meat. The fossils sites also give an impression of group activity and some sort of social organization. Some scientists even conjecture that Homo Habilis saw the beginning of ritual and folklore typical human endeavors.
. Like all primates Homo Habilis subsisted mainly on a diet of plant parts such as fruits and barriers and also roots and tubers which they dug up using pointed bones and also stone tools. In addition, the diet also included raw meat which they probably scavenged from the kills of other carnivores. Although they were more enterprising than the earlier apes
, Homo Habilis in all probability made their homes in the trees to escape from carnivores.
We know this from their skeletal remains: they reveal that Homo Habilis had long arms well adapted to tree climbing. From the study of fossils remains, other interesting facts about Homo Habilis have come to light.
Patterns of tooth growth indicate that the family life at Olduvai was more like that of an ape than of humans. They indicate that Habilis children grew up nearly twice as fast as children of modern humans. This would also mean that our early ancestors would have been young adults by age 12, parents in their teens, and become old by the time they turned 30.
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Homo Habilis with much greater brain power and stone tools must have had a wider choice of food than the more primitive Australopithecus Boisei.. Records show that after the global freeze about 6 million years ago the climate had warmed up again. But, around 2.5 million years ago temperature dropped again bringing in a little of ice age.
It was during this period, it is now believed, that the early ancestors of man split into two diverging branches. One branch leading to Australopithecus Robustus and the other to Homo Habilis, which subsequently led towards modern humans.
By the time Homo Habilis died some 1.5 million years ago, a new, more advanced human ancestor had appeared on the scene. Named Homo erectus or the upright man, this large brained ancestor of ours was a true wanderer. It would become the first early humans to leave the cradle of the African continent and spread around the world.
Early Tools
The oldest obviously manufactured tools were discovered in 1931 by L. S. B. and Mary Leakey at Olduvai Gorge, Tanzania along with the fossils record of the species Homo habilis.
This site gave the tools their name-Oldowan pebble tools. The oldest tools from Olduvai are about 1.8 million years old. Still older stone tools have been found in Ethiopia, Congo, and Malawi.
Stone tools consist of cores and flakes. The core is the piece of rock from which flakes are removed; the core can be worked to become a tool itself..Homo Habilis being capable of using his hand was the first species in the line of human evolution to manufactured stone tools for his sustenance. This species is popularly known as the handy man.
Homo Erectus: The Erect Man(1 million years ago) |
| Homo-Erectus |
In the last decade of the nineteenth century an unusual fossil discovery was made in the island of Java in South-East Asia , it would be known as Java Man .. Forty years later, in China, a young paleontologists, named W.C. Pei, found a similar skull cap and it would be known as peking man.. The fossils of Peking man were less than 1 million year old. Today, of course, we know about both Java man and Peking man belonged to the same species Homo Erectus,
In facial appearance, Homo Erectus was not much different from its predecessor, homo Habilis.. But what distinguished it from its predecessors was its rather large brain, with a volume close to 1000 cc, compared to 680 cc for Homo Habilis and 1,350 cc for modern humans. With its larger, more complex brain
, Homo Erectus certainly had better intelligence than its predecessor and must have developed intellectual curiosity none of its predecessors was endowed with. it may even have had some capability of speech. We can tell about the higher intelligence of Homo erectus from the variety of advanced stone tools and weapons found at the excavation sites.
Evidence from china and elsewhere where charcoal has been found at several sites suggests that Homo Erectus also know how to control fire and cook food. This may have been open of the factors that led to a reduction in teeth size in later human ancestors, because chewing cooked food needs less force than chewing n raw meat or uncooked food.
The Great Exodus and Aftermath( Homo Erectus )
The larger brain capacity may also have endowed Homo Erectus with an urge to venture out beyond its immediate neighborhood in search of new pastures.
Another factor that may have made Homo Erectus move out of Africa could be population pressure due to increasing numbers at the few favorable locations
Hunting and foraging skills and substantially improved capability of exploiting the environment, Homo erectus may not have faced much difficulty in moving into a new unexplored territory. And so, with Homo erectus began the big exodus out of Africa, about 1 million years ago.
They spread far and wide as fossil evidences from China, South-East Asia and from the Narmada Valley in India show. Surprisingly, no definitive fossil evidence of the presence of Homo Erectus has been found in Europe.
When populations of Homo Erectus began to move out of Africa about 1 million year ago, they carried their improved knowledge of tool making with them which was crucial for their survival in an unknown, hostile environment.
As they spread across Europe and Asia, they improved their tool-making techniques-broad flakes gave way to narrow blades.
Besides improved tool making, Homo Erectus migrant brought in a different kind of change. Faced with unfamiliar environments in their new homes, they rapidly evolved area-specific adaptations which helped them cope more successfully with the new environments.
.Homo Erectus pushed the hominin range beyond Africa-to Asia, Europe and Eurasia , as evidenced from the discoveries of fossils record from China and Indonesia in the east besides Africa. Homo Erectus first arose about 1.6 million years ago and is believed to have lived for at least 600,000 years at a time when the transition to Homo sapiens took place.
The fossil finds of Homo Erectus indicate several first happenings in human history. For the first time man became from being an opportunistic scavenger to a cooperative and big game hunter.
For the first time he had come to know the use of fire. From being a mere stone scrapper, he became a systematic tool maker. There is evidence to indicate that he had home bases of campsites from where he operated.
.Homo Erectus fossils found for the first time from outside Africa, in Eurasia. Homo erectus variously named as Pithecanthropus, Sinanthropus and Atlanthropus, first appeared during the Pleistocene interglacial period.
The later populations of Homo Erectus were known as cave man or ape man.
The fossil evidence did suggest that Homo Erectus was very clever as compared to the apes but dull as compared to the modern man.
. Tool of Homo erectus
Two specific skills of Homo Erectus make them special from all his predecessors: i) skills as an efficient tool maker ii) skills as a cooperative game hunter.
According to historians both the skills could be associated with the larger brains they had. The tools made by Homo Sapiens were more polished than those of their immediate ancestors. The Homo Erectus Species was the real author of lower Paleolithic age. Stone tool making industry can be said to fall into two categories:
Big Game Hunting
The most important event that led to the evolution of modern man is his transition from being a hunter-gatherer to that of a big game hunter. During the middle Pleistocene times there were huge herds of very large mammals. Bones of such large mammals were found associated with the human fossil finds and the contemporary fossil tools.
Initially the big game hunting was probably not carried out on a large scale and might have been cooperative venture. It could be true that although the hunting was a cooperative venture, Homo Erectus could not have detailed any specific plan in advance because of the lack of communication skills. But the cooperative venture served one big purpose namely it enabled the formation of multi-family groups and socializing tendencies.
In other words, big game hunting could have been the reason for the development of different social roles for males and females. This means the division of labour was being established and the role of female was getting confined mostly to child bearing and rearing children along with gathering of vegetal matter and slow game.
The big game hunting brought certain changes in the physical structure of the human beings. Man hunted the animals during the day time. This meant that the hard work of chasing and killing animals had to be done in the hot sun. Selection during these times favoured individuals that lost the metabolic heat faster than their fellow individuals. During these times possibly man had lost the thick hair of body and developed a high density of sweat glands in the skin. Man could effectively evaporate and cool all over the body.
Invention and Use of Fire
Another tool that Homo Erectus has learnt to use was fire and in fact man had multiple uses for fire. It is not very clearly known how man had learnt to tame the fire but he understood that it was a source of warmth at a time when the thick hair from the body was being eliminated.
Man also found use in fire in scaring of large carnivores. With a generalized tooth row that he was now developing, it became important for him to soften the tough meat and vegetables.
Fire was also used to harden the pointed wooden stakes so that it is converted into a spear.
Finally, fire also contributed to the development of social behaviour.
The era of Homo erectus should have probably come to an end some 275 thousand years ago, but by that time all those salient characters that are found in modern man had come to be established in Homo erectus.
It has not been possible for the paleontologists and anthropologists to determine precisely the time of transition from Homo erectus to Homo sapiens although the first fossils of Homo sapiens were at least 300,000 years old.
opithecine period, is joined by Asia and Europe during the Homo Erectus and Homo Sapiens periods of hominind evolution.
Recent discoveries, along with reinterpretation of the dating and the anatomical relevance of some earlier finds, are filling in the gap between Homo Erectus and archaic Homo Sapiens.
Archaic Homo Sapiens (300,000 to 28,000 B.P.) encompasses the earliest members of our species, along with the Neanderthals (130,000 to 28,000 B.P.) of Europe and the Middle East and their Neanderthal-like contemporaries in Africa and Asia.
. Homo sapiens first appeared in the fossil record between 200,000 to 300,000 years ago. There are only slight physical differences between Homo Erectus and Homo Sapiens and the transition between the two species is obvious from the earliest known groups of Homo Sapien, the Neanderthal man.
Whereas Homo Sapien is characterized by a large and round brain case, smaller brow ridges and a more pronounced chin as compared to pithecanthropus, Neanderthals were more or less intermediate
The first Neanderthal was found in 1856 in a German valley called Neander Valley-tal is the German word for valley. Scientists had trouble interpreting the discovery. It was clearly
human, yet different enough from modern people to be considered strange and abnormal.
There have been numerous subsequent discoveries of Neanderthals in Central Europe and the Middle East.
, Neanderthals man again faced extreme cold as the Wurm glacial began. To deal with that environment, they wore clothes, made elaborate tools, and hunted reindeer, mammoths, and woolly rhinos.
The Neanderthals were stocky, with large trunks relative to limb length that minimizes surface area and thus conserves heat
. Another adaptation to extreme cold was the Neanderthal face, which has been likened to a Homo erectus face that has been pulled forward by the nose. This extension increased the distance between outside air and the arteries that carry blood to the brain and was adaptive in a cold climate.
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Neanderthal man was distributed all over Europe, Asia and Africa. Their cranial capacity was larger than that of modern man.
Neanderthals are known for their fine tool industry, the Mousterian industry in which the hand axe was slowly replaced by various tools. With prominent eyebrow ridges, they had a receding forehead and the cranial capacity was greater than that of modern man averaging about 1450 C.C. The teeth and jaws were large and heavy as compared to modern man and he had a receding chin. Indications are that he had a powerful neck musculature, robust limb bones and a skeleton more adapted to higher levels of activity and stress. Anatomy of the hand indicated a powerful grip. The stature was 1.5 meters and he was a cave dweller. Culturally Neanderthals appeared to be more advanced.
They had the habit of burying dead ones with reverence as was evidenced by the presence of flowers in the burial centers. This group was biologically very successful and consisted of a homogeneous and widely distributed people.
The Homo Sapien Sapien: Cro-Magnon Man
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| homo-sapiens-sapiens |
Modern humans, Homo Sapiens Sapiens appeared in fossils some 33 thousand years ago. The first fossil was discovered from the Cro-Magnon shelter in France and hence the fossil was known as Cro-Magnon man.
Subsequently many such fossils were known from France, Italy and Middle East
. All such fossils exhibited reduced brow ridges, steep forehead, high rounded cranial vault, short face and pronounced chin. Being bulky, they were not as tall as Neanderthals. Structurally the Cro-Magnon man had a lot of resemblance to modern Europeans.
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Fishhooks and harpoons confirm an increased emphasis on fishing. One could obtain in fossils long thin blades of various types. Further, Cro-Magnons had a taste for art. They made beads, carved statues and even engraved pictures. The cave paintings made by these men are a record of their aesthetic sense.
Their burials were ceremonial and gave an indication of their cultured life. It could be said that with the appearance of Cro-Magnon, the modern human, the morphological evolution of humans is more or less complete and any further progress is relate to culture and language.
A significant shift in the pattern of human activity has occurred beginning about 10,000 years ago. This shift manifested itself in various aspects of his life. For instance, there was a shift from hunting and gathering to agriculture. There was a shift in the tool making process also. From the Paleolithic age which was marked by making stone tools, he began to make his implements first in bronze and then in iron.
And beginning 5,000 years ago special occupations developed, the cities began to be formed and the development of various aspects of culture such as writing, history, wealth, leisure, science and arts took place. This can briefly be the evolution of modern humans.
CONCLUSION:
In this article we reconstruct certain aspects of human evolution based on the scantly fossil evidence that is available. The fact of evolution was known before Darwin and Wallace.
Humans, apes, monkeys, and prosimians are primates.
Anthropoids include humans, apes, and monkeys. The great apes are Orang-utans, gorillas, and chimpanzees. The African apes—chimps and gorillas—are our nearest relatives
. The human evolutionary history can be traced back to 60 million years that is to the cretaceous age of the Palaeocene times.
. Based on fossil evidence it is observed that the hominid lineage separated from the australopithecines some 3.5 million years ago.
The australopithecines became extinct with Australopithecus Robustus and Australopithecus Boisei.
The hominid lineage passed through different stages such as Homo Habilis and Homo erectus before the modern man evolved.
A race of modern human species the Neanderthals were possibly the connecting link between Homo Erectus and Homo Sapiens.
The first Homo Sapiens Sapiens, the Cro-Magnon man possibly represented the transition between the Neanderthal man and the modern man.
The process of evolution is still continuing. It may be happening that still human being is under the process of biological evolution but owing to our short life span we are unable to observe. We are only observing the evolution of mankind in the cultural part, where it still evolving.
Key word:
Australopithecus Afarensis: Early form of Australopithecus(3.3–3.0 m.y.a.);
Archaic Homo Sapiens: Early Homo sapiens, consisting of the Neanderthals of Europe and the Middle East, the Neanderthal-like hominins of Africa and Asia, and the immediate ancestors of all these hominins; lived from about 300,000 to 28,000 B.P
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Australopithecines: Varied group of early hominins.
Hominid: A member of the taxonomic family that includes humans and the African apes and their immediate ancestors.
Hominin: A member of the human lineage after its split from ancestral chimps, gorillas.
Homo habilis: Term coined by L. S. B. and Mary Leakey; immediate ancestor of H. erectus; lived from about 2.0 to 1.7 m.y.a..
. Neanderthals: Members of an archaic H. Sapiens group that lived in Europe and the Middle East between 130,000 and 28,000 B.P.
Oldowan: Earliest (2.5 to 2.0 m.y.a.) stone tools; first discovered in 1931 by L. S. B. and Mary Leakey at Olduvai Gorge.
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