The evolution of life began in the oceans. About four hundred million years ago the first land based creatures emerged. Some of these gradually evolved into the large reptiles who were later displaced by mammals. Mammals are warm-blooded creatures having greater capacity to learn from experience than other animals and this capacity has reached its highest development in the human species. Our closest relatives are chimpanzee, gorilla and oranguatan. Though similarities between man and other animal forms were discovered by Linnaeus who grouped men ,the great ape and monkeys in a single order, primates, the three main theories are Lamarckism, Darwinism and Synthetic theory.
Lamarck is chiefly remembered for his belief in the inheritability of acquired character which is disputed. But he is credited in the history of evolutionary thought for recognizing and stating for the first time that evolution is a general fact covering all forms of life and it is a gradual process.
The scientific establishment of the theory of evolution was mainly the work of Charles Darwin. In his book 'The Origin of Species'1859 he showed that human evolution has occurred through the process of natural selection. The main points of this theory are:
Darwin's natural selection serves as the corner-stone of the modern synthesis, but the mutation theory,Mendelian genetics and the statistics of population dynamics are also very important components of its foundation.
The basic postulate of the synthetic theory is that evolution proceeds principally as a result of the interaction between five indispensable processes-
This is also called Neo-Darwinism.
Dryopithecus: This genus lived in Africa,China,India and Europe. The genetic title dryopithecus means oak wood apes because it is believed that the environmental conditions were such at that time with densely forested tropical lowlands and the members might have been predominantly herbivorous.
Ramapithecus: The first remains of Ramapithecus were discovered from Shivalik hills in Punjab and later discovered in Africa and SaudiArabia.The region where Ramapithecines lived was not merely forest but open grassland. A hominid status for them is claimed on two grounds: Fossil evidence indicating adaptation including robust jaws, thickened tooth enamel and shorter canines. Extrapolation regarding upright posture and the use of hands for food and defense.
Australopithecus: This genus is the immediate forerunner of the genus Homo.The first Australopithecine find was made in 1924 at Taung a limestone quarry site in South Africa by Raymond Dart. They walked erect, lived on the ground and probably used stones as weapons to hunt small animals. They weighed 60 to 90 pounds and were about 4 feet tall.
Home Erectus: The first evidence of the Homo species was discovered in Java by Eugene Dubois in 1891.He named his find as pithecanthropus erectus meaning the erect ape man. It is said to be the missing link. Another find was made in China ,south-west of Peking called Peking man. These had larger cranial capacity then Australopithecus lived in communal existence and used fire. The cranial capacity of Homo erectus which include Java man and Peking man varied from about 775 to nearly 1300 CC.The Acheulean tool tradition is associated with the Homo Erectus way of life. The stone tools were largely made of quartz. Bone tools and wooden tools like wooden spears have also been discovered. There is evidence of big game hunting which indicates that there must have been collective cooperative hunting. The Homo Erectus seem to be cave-dwellers. An important advancement is that there is evidence of the use of fire.
Homo Sapiens Neanderthalensis : The Home erectus gradually evolved into the Homo Sapiens. In this transitional event two sub-species of the Homo sapiens have been identified. One the primitive man who has been labeled Homo sapien Neanderthal and two the modern man who is called Homo sapiens sapiens. Most of the evidences about the primitive man that have been unearthed are 75,000 years old. The first fossil that was found of the Neanderthal type was a skull cap found in Germany. The cranial capacity of Neanderthal exceeded that of the modern man.It ranged from 1200 to 1610 c.c.Their culture has come to known as Mousterian culture. A few small hand axes are also found. For the first time pointed stone flakes which seem certainly to be spearheads have also been found. There caves were made more comfortable for winter dwelling by placing a fire work with holes at the entrance of the cave and by covering it with stretched hide. The Neanderthals were capable of big game hunting, including elephants, rhino etc.
Homo Sapiens Sapiens: The first skeletal remains of Homo sapiens sapiens were found in Europe and were named Cro-Magnon. In the Homo sapiens sapiens there is final reduction of the jaws, the appearance of modern man's chin and of the rounded skull.Mean cranial capacity was about 1350 c.c.Modern man is very closely related to Cro-magnon.Their culture which dates back to 35,000 years is also called upper Paleolithic culture. Hunting and gathering seem to have been the primary methods of food gathering. The first appearance of art was during this time. The drawings on cave walls were mainly of animal figures.