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The Story of Human Evolution (FROM THE BEGINNING OF LIFE)

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1. The Story of Human Evolution :

The humam evolution is the lengthy process of change by which people originated from ape like ancestors.It is the evolutionary process that led to the emergence of anatomically modern humans, beginning with the evolutionary history of primates in particular genus Homo and leading to the emergence of Homo sapiens as a distinct species of the hominid family, the great apes.

The story of human evolution is enormously long, and somewhat complicated. It is possible to trace these developments back to between 36 and 24 mya. We sometimes find it difficult to conceptualise such long spans of time. 

If you consider a page of your book to represent 10,000 years, in itself a vast span of time, 10 pages would represent 100,000 years, and a 100 pages would equal 1 million years. To think of 36 million years, you would have to imagine a book 3,600 pages long! That was when primates, a category of mammals, emerged in Asia and Africa. Subsequently, by about 24 mya, there emerged a subgroup amongst primates, called hominoids. This included apes. And, much later, about 5.6 mya, we find evidence of the first hominids. 

While hominids have evolved from hominoids and share certain common features, there are major differences as well. 

Hominoids have a smaller brain than hominids. They are quadrupeds, walking on all fours, but with flexible forelimbs. Hominids, by contrast, have an upright posture and bipedal locomotion (walking on two feet). There are also marked differences in the hand, which enables the making and use of tools. We will examine the kinds of tools made and their significance more closely later. 

Two lines of evidence suggest an African origin for hominids. 

First, it is the group of African apes that are most closely related to hominids. 

Second, the earliest hominid fossils, which belong to the genus Australopithecus, have been found in East Africa and date back to about 5.6 mya. In contrast, fossils found outside Africa are no older than 1.8 million years. Hominids belong to a family known as Hominidae, which includes all forms of human beings.

The distinctive characteristics of hominids include a large brain size, upright posture, bipedal locomotion and specialisation of the hand. Hominids are further subdivided into branches, known as genus, of which Australopithecus and Homo are important. Each of these in turn includes several species. 

The major differences between Australopithecus and Homo relate to brain size, jaws and teeth. The former has a smaller brain size, heavier jaws and larger teeth than the latter. Virtually all the names given by scientists to species are derived from Latin and Greek words. 

For instance, the name Australopithecuscomes from a Latin word, 'austral', meaning ‘southern' and a Greek word, 'pithekos, meaning 'ape. The name was given because this earliest form of humans still retained many features of an ape, such as a relatively small brain size in comparison to Homo, large back teeth and limited dexterity of the hands. Upright walking was also restricted, as they still spent a lot of time on trees. They retained characteristics (such as long forelimbs, curved hand and foot bones and mobile ankle joints) suited to life on trees. Over time, as tool making and longdistance walking increased, many human characteristics also developed. 

The remains of early hunans have been ciassified into different species. These are often distinguished from one another on the basis of differences in bone structure. For instance, species of early humans are differentiated in terms of their skull size and distinctive jaws. These characteristics may have evolved due to what has been called the positive feedback mechanism.. For example, bipedalism enabled hands to be freed for carrying infants or objects. In turn, as hands were used more and more, upright walking gradually became more efficient. Apart from the advantage of freeing hands for various uses, far less energy is consumed while walking as compared to the movement of a quadruped

However, the advantage in terms of saving energy is reversed while running. There is indirect evidence of bipedalism as early as 3.6 mya. This comes from the fossilised hominid footprints at Laetoli, Tanzania. Fossil limb bones recovered from Hadar, Ethiopia provide more direct evidence of bipedalism. Around 2.5 mya, with the onset of a phase of glaciation (or an Ice Age), when large parts of the earth were covered with snow, there were major changes in climate and vegetation. 

Due to the reduction in temperatures as well as rainfall, grassland arcas expanded at the expense of forests, leading to the gradual extinction of the early forms of Australopithecus (that were adapted to forests) and the replacement by species that were better adapted to the drier conditions. Among these were the earliest representatives of the genus Homo. 

Homo is a Latin word, meaning 'man', although there were women as well! Scientists distinguish amongst several types of Homo. The names assigned to these species are derived from what are regarded as their typical characteristics. So fossils are classified as Homo habilis (the tool maker), Homo erectus (the upright man), and Homo sapiens (the wise or thinking man). 

Fossils of Homo habilis have been discovered at Omo in Ethiopia and at Olduvai Gorge in Tanzania. The earliest fossils of Homo erectus have been found both in Africa and Asia: Koobi Fora, and west Turkana, Kenya, Modjokerto and Sangiran, Java. As the finds in Asia belong to a later date than those in Africa, it is likely that hominids migrated from East Africa to southern and northern Africa, to southern and north-eastern Asia, and perhaps to Europe, some time between 2 and 1.5 mya. This species survived for nearly a million years. 

In some instances, the names for fossils are derived from the places where the first fossils of a particular type were found. So fossils found in Heidelberg, a city in Germany, were called Homo heidelbergensis, while those found in the Neander valley (see p. 18) were categorised as Homo neanderthalensis. 

The earliest fossils from Europe are of Homo heidelbergensis and Homo neanderthalensis. Both belong to the species of archaic (that is, old) Homo sapiens. The fossils of Homo heidelbergensis (0.8-0.1 mya) have a wide distribution, having been found in Africa, Asia and Europe. 

The Neanderthals occupied Europe and western and Central Asia from roughly 130,000 to 35,000 years ago. They disappeared abruptly in western Europe around 35,000 years ago. 

In general, compared with Australopithecus, Homo have a larger brain, jaws with a reduced outward protrusion and smaller teeth. An increase in brain size is associated with more intelligence and a better memory.

2. The History of Modern Human Beings :

Modern humans primarily Homo sapiens are the only extant members of Hominina tribe for human tribe),a branch of the tribe hominini belonging to the family of great apes. Modern humans orginated in Africa within the past 200,000years before migrating across the world. The issue of the place of origin of modern humans has been much debated. Two totally divergent views have been expounded, one advocating the regional continuity model (with multiple regions of origin), the other the replacement model (with a sinfgle origin in Africa). According to the regional continuity model, the archaic Homo sapiens in different regions gradually evolved at different rates into modern humans, and hence the variation in the first appearance of modern humans in different parts of the world. The argument is based on the regional differences in the features of present-day humans. According to those who advocate this view, these dissimilarities are due to differences between the pre-existing Homo erectus and Homo heidelbergensis populations that occupied the same regions.

The replacement model visualises the complete replacement everywhere of all older forms of humans with modern humans. In support of this view is the evidence of the genetic and anatomical homogeneity of modern humans. Those who suggest this argue that the enormous similarity amongst modern humans is due to their descent from a population that originated in a single region, which is Africa. The evidence of the earliest fossils of modern humans (from Omo in Ethiopia) also supports the replacement model. Scholars who hold this view suggest that the physical differences observed today among modern humans are the result of adaptation (over a span of thousand years) by populations who migrated to the particular regions where they finally settled down.

3. Early Humans: Ways of Obtaining Food :

Early humans would have obtained food through a number of ways, such as gathering, hunting, scavenging and fishing. Gathering would involve coliecting plant foods suchas seeds, nuts, berries, fuits and tubers. That gathering was practised is generally asumed rather than conclusively established, as there is very little direct evidence for it. While we get a fair amount of fossil bones, fossilised plant remains are relatively rare. The only other way of getting information about plant intake would be if plant remains were accidentally burmt. This process results in carbonisation. In this form, organic matter is preserved for a long span of time. However, so far archaeologists have not found much evidence of carbonised seeds for this very early period. In recent years the term hunting has been under discussion by scholars. Increasingly, it is being suggested that the early hominids scavenged or foraged* for meat and marrow from the carcasses of animals that had died naturally or had been killed by other predators. It is cqually possible that small mammals such as rodents, birds (and their eggs), reptiles and even insects (such as termites) were eaten by early hominids. Hunting probably began later about 500,000 years ago. 

The earliest clear evidence for the deliberate, planned hunting and butchery of large mammals comes from two sites: Boxgrove in southern England (500,000 years ago) and Schoningen in Germany (400,000 years ago). Fishing was also important, as is evident from the discovery of fish bones at diferent sites. From about 35,000 years ago, there is evidence of planned hunting from some European sites. Some sites, such as Dolni Vestonice (in the Czech Republic, see Map 2), which was near a river, seem to have been deliberately chosen by early people. Herds of migratory animals such as reindeer and horse probably crossed the river during their autumn and spring migrations and were killed on a large seale. The choice of such sites indicates that people knew about the movement of these animals and also about the means of killing large numbers of animals quickly.

4. Early Humans - From Trees, to Caves and Open-air Sites :

Archaeologists suggests that early humans consumed most of the food where they found it. We are on surer ground when we try to reconstruct the evidence for patterns of residence. One way of doing this is by plotting the distribution of artefacts. For example, thousands of flake tools and hand axes have been excavated at Kilombe and Olorgesailie (Kenya). These finds are dated between 700,000 and 500,000 years ago How did these tools accumulate in one place? It is possible that some places, where food resources were abundant, were visited repeatedly. In such areas, people would tend to leave behind tracen of their activities and presence, including artefacts. The deposited artefacts would appear as patches on the landscape, The places that were less frequently visited would have fewer artefacts, which may have been scattered over the surface, It is also important to remember that the same locations could have been shared by hominids, other primates and carnivores Between 400,000 and 125,000 years ago, caves and open-air sites began to be used. Evidence for this comes from sites in Europe. In the Lazaret cave in southern France, a 12x4 metre shelter was built against the cave wall. Inside it were two hearths and evidence of different food sources: fruits, vegetables, secds, nuts, bird eggs and freshwater fish (trout, perch and carp). At another site, Terra Amata on the cOast of southem France, flimsy shelters with roofs of wood and grasses were built for short-term, seasonal visits. Pieces of baked clay and burnt bone along with stone tools, dated between 1.4 and 1 mya, have been found at Chesowanja, Kenya and Swartkrans, South Africa. Were these the result ofa natural bushfire or volcanic eruption? Or were they produced through the deliberate, controlled use of fire? We do not really know. Hearths, on the other hand, are indications of the controlled use of fire. This had several advantages- fire provided warmth and light inside caves, and could be used for cooking. Besides, fire was used to harden wood, as for instance the tip of the spear. The use of heat also facilitated the flaking of tools. As important, fire could be used to scare away dangerous animals

5. Tools of the Early Humans :

The earliest evidence for the making and use of stone tools comes from sites in Ethiopia and Kenya. It is likely that the carliest stone tool makers were the Australopithecus. As in the case of other activities, we do not know whether tool making was done by men or women or both. It is possible that stone tool makers were both women and men. Women in particular may have made and used tools to obtain food for themselves as well as to sustain their children after weaning. About 35,000 years ago, improvements in the techniques for killing animals are evident from the appearance of new kinds of tools such as spearthrowers and the bow and arrow. The meat thus obtained was probably processed by removing the bones, followed by drying, smoking and storage. Thus, food could be stored for later consumption. 

There were other changes, such as the trapping of fur-bearing animals (to use the fur for clothing) and the invention of sewing needles. The earliest evidence of sewn clothing comes from about 21,000 years ago, Besides, with the introduction of the punch blade technique to make small chisel like Tools,it was now possible to make engravings on bone, antler, ivory or wood.

6.Modes of Communication: Language and Art :

Among living beings, The humans alone have a language among the living beings. It developed through various stages from ancient period.There are several views on language development: (1) that hominid language involved gestures or hand. movements; (2) that spoken language was preceded by vocal but non-verbal communication such as singing or humming: 3) that human speech probably began with calls like the ones that have been observed among primates. Humans may have possessed a small number of speech sounds in the initial stage. Gradually, these may have developed into language. When did spoken language emerge? It has been suggested that the brain of Homo habilis had certain features which would have made it possible for them to speak. Thus, language may have developed as early as 2 mya. The evolution of the vocal tract was equally important. This occurred around 200,000 years ago. It is more specifically associated with modern humans. A third suggestion is that language developed around the same time as art, that is, around 40,000-35,000 years ago. 

The development of spoken language has been seen as closely connected with art, since both are media for communication. Hundreds of paintings of animals (done between 30,000 andl2,000 years ago) have been discovered in the caves of Lascaux and Chauvet, both in France, and Altamira, in Spain. These include depictions of bison, horses, ibex, deer, mammoths, rhinos, lions, Dears, panthers, hyenas and owls. paintings For example, why do some areas of ca Several explanations have been offered to these cave paintings depicting animals. One is that because of the importance of hunting, the paintings of animals were associated with ritual and magic. The act of painting could have been a ritual to ensure a successful hunt. Another explanation offered is these caves were possibly meeting places for small groups of people or locations for group activities. These groups could share hunting techniques and knowledge, while paintings and engraving served as the media for passing information for one generation to the next generation...

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