Man as a species evolved in the same general way as other species. The raw material for organic evolution is provided by payment changes that occur. In the hereditary units called genes. These changes occur spontaneously, although such changes can also be induced. Once the changes takes place, nature has to act as moderator. Nature determines whether or not these changes are going to be helpful to the organism.
Nature may either select the animal or eliminate it depending upon whether changes in the genes will confer advantages or disadvantages on the animal.
How Do We Go About Studying Evolution
It is not easy to study the evolution of any particular species, let alone man. For one things, evolution is a slow process of change. It takes millions of years for a species to come in being. It means that one has to go back in time and recreate the past to understand a lot of things about evolution.
Study of fossils
To construct the course of evolution i.e., to find out the successive changes in living forms in the past, we have to study the fossils. Fossil may be defined as any relic of an organism buried in the earth or rocks by natural causes in past geologic time. The evidence in the form of bones, teeth, shells, impressions, etc. about 99% of fossils consists of hard part of the body. Formation of fossil is called fossilization. The most likely places for fossil formations are muddy or sandy mud of lake and ocean. Fossil may become uncovered by erosion. The scientific study of fossil is called paleontology. Whenever a paleontologist changes upon a fossil, the remove extraneous materials attached to the actual part of the dead animal.
Determination of age of fossils To find out the historical sequence of life, it is important to find out the absolute age of fossil. It is difficult task. But it had been made possible by finding out the radioactive decay of elements in the fossil. Normally, non radioactive and radioactive forms of a given chemical exist in the nature. Over a period of time, the radio active portions declines i.e., it decays at certain rate. By finding out this ratio and knowing the rate of decay, it becomes easy to calculate the absolute rate of materials under examination.
Man’s Family Tree
TIME:70 x 106 years ago
About 70 million years ago there was mouse like animals. They were called shrews. They started living on trees. Their fingers had moveable joints. But hands and feet of these animals are not specialized as we find in horses, bats, and whales. These tree-dwellers had visual accuracy but their sense of smell was not powerful. We call these tree-dwellers primates. Although primates did not show any anatomical specializations, their brain was developing. The conformation, arrangement and number of teeth in both the jaws were such that they could eat vegetables as well as meat, thus, they were called omnivorous.
From this group, primates, different subgroups of animals started emerging.
Subgroup I (Lemurs)
This subgroup has retained the features of the original group in that the members have retained long snouts and tails. They had flat nails. Lemurs are found in Madagascar (Figure 6.1).
Subgroup II (Tarsiers)
This subgroup did not have snouts. The flattening of the region between the lip and nose, gave them a different look. We can say that they have some kind of face. Their eyes also shifted from lateral sides towards the nose bridge. Tarsiers are found in Indonesia and South Asia (Figure 6,1)
Subgroup III (New world Monkeys)
Monkeys also have flattened face . Some monkeys had very strong tails which were used for grasoing the branches of trees and also for hanging (Prehensile tall). These are called New World Monkeys and are confined to South and Central America (Figure 6.1).
Subgroup IV (Old World Monkeys)
These are also monkeys with the difference that they cannot use their tails for grasping or hanging (Figure 6.1). Such tails are called nonprehensile. All monkeys adopt sitting posture at rest and free their forelimbs for touching objects. Moreover, monkeys have colour vision and enlarged brain.
Subgroup V (Apes and men)
This subgroup developed limb sockets and upright posture. They became tree-walkers. Their tail became shorter. The predecessor of both ape and man was propliopithecus (fossil ape).
TIME: 30 x 106 years ago
The subgroup V split into two sub line. One of them (pongid) developed into apes. The other sub line (hominid) gave rise to t he family of man. A fossil named Dryopithecus was found in Europe and India. This fossil is believed to be close to the point of divergence of two sub lines which occurred about 30 million years ago. The four genera of apes are gibbons, orangutans, chimpanzees and gorillas. Gibbons are Light-weight and fully adapted to tree dwelling. The other three are heavy-bodied.
The sub line (hominid) which gave rise to man, left the trees. What forced them to come to the ground? May be, they wanted a cooler climate or they wanted to move from one tree to another. This sub line which gave rise to man is not richly evidenced with fossil records. If a hominid used sticks or stones already available around it, we call him pre-human. But if he designed a crude natural object into something new, we call him human.
TIME: 14x106 years ago
One of the most signifies hominid fossils in the direct line of man’s ancestor were that of Ramapithecus wickeri who lived 14 million years ago.
The characteristics of R. wickeri were as follows:
He spent more time on ground that on trees.
His arms were capable of full-circle rotation.
He was omnivorous.
His poster was bipedal.
In the Siwalik Hills of North-West India, the fossil of Ramapithecus was found by G. E. Lewis.
TIME: 1.75 x 106 years ago
Zinjanthropus is supposed to be the next in order of seniority. Its fossil was found in East Africa by Leakeys.
The characteristics of zinjanthroupus were as follows:
His jaw muscles were such as to suggest some power of speech.
Forehead was almost absent
Brain was not larger than 600 cm3
Zinjanthropus was called nut-cracker man
TIME: 1.0 * 106 Years ago
Australopithecus Africans (southern ape) is supposed to have lived 1 million years ago. This fossil was reported by R A Dart. But the brain of A. Africans was not larger than that of Zinjanthropus.
TIME: 0.5 * 106 Years ago
Pithecanthropus erectus (Homo erectus) is a much better known hominid. If a hominid used ready-made stones and sticks of the environment, he is called prehuman. If a hominid made and fashioned tools and used them, he is called ‘man’. Homo erectus made tools from stones and bones. Hence the word ‘man’ is applied from here onwards.
The lower law of Pithecanthropus was discovered in Java by a Dutch doctor, Eugene Dubois. He said that the lower jaw belonged to a prestroic man, Pithecanthropus erectus. This fossil was subsequently named Homo erectus (Java man). A contemporary of this Home erectus fossil was Sinanthropus (Peking man_. This fossil was found in the caves near Peking. Peking man is called Homo erectus pekinensis.
The characteristics of Homo erectus were as follows:
His brain volumes averaged 900 cm3
He was probably a cannibal (one who kills and eats his own species)
He was also a hunter
He used tools made up of stones
He cooked food
TIME: 0.15 * 106 Years ago
The best known fossil record of prehistoric man was found in the Neander valley in Germany. He has been named Homo sapiens neandethalensis (Neanderthal man). Neanderthal man arose 150000 years ago but became extinct 250000 years ago.
The characteristics of Neanderthal man were as follows:
Brain volume was 1450 cm3
The brain was proportioned differently from that of modern man.
The back of the skull was projected out. In modern man this paper is rounded.
The forehead was low and receding
Eyebrow bridge was heavy
Jaw was massive almost without a chin
They were nomadic
They lived in caves
They fashioned a variety of tools and weapons
Neanderthal man was a subspecies of our own species. When Neanderthal man existed, there were populations of man in other papers of the world also. For example, in South-East Asia, there lived Solo man. Rhodesian man lived in Africa, and Palestinus man lived in Asia. Therefore, we can say that Neanderthal man was not our immediate ancestor. It appears most reasonable to believe that modern man and late Neanderthal man had some common ancestor.
TIME: 50000 Years ago (0.05 * 106)
Cro-Magnon man (Homo sapiens fossils) lived between 50000-20000 years ago. They may have been responsible for the extinction of Neanderthal man.
The characteristics of Cro-Magnon were:
6 feet tall
With brain volume 1700 cm3
Painter. (They painted cave walls)
Able to sew animal skin with bone needles
Cro-Magnon was contemporary of other groups of Homo sapiens. The racial subdivision of modern man might have taken place at that time.