Though life began on the earth around 3500 million years ago, it was confined to plants and animals for many millennia.
Humans appeared on the earth in pre-Pleistocene and early Pleistocene times. Several types of humans, called hominids, lived in southern and eastern Africa about 6 million years ago.
The earth is over 4600 million years old. The evolution of its crust shows four stages. The fourth stage is called the quaternary. It is divided into two epochs called Pleistocene (ice age) and Holocene (post-ice age).
The first epoch lasted from 2 million BC to 12,000 BC, the second began in about 12,000 BC and continues to this day.
The earliest humans were not very different from apes which first developed 30 million years ago. The birth of the creature called Australopithecus was the most momentous step in the evolution of the human line. Australopithecus is a term that originated in Latin and means southern ape. This species or family possessed both apelike and human characteristics, and originated roughly between 5.5 million and 1.5 million years ago. This creature was bipedal and pot-bellied, with a very small braincase measuring 400 cubic centimeters.
The Australopithecus was marked by some elements found in other living beings called homos or human beings. Humans form part of the hominid line of evolution and Australopithecus was the last of the pre-human hominids. That is why this species is also called proto-human. The first important Homo or human was Homo habilis found in eastern and southern Africa about 2—1.5 million years ago. Homo habilis means a handy or skillful man. This first real human broke stone into pieces and sharpened the latter to use as tools. Fractured pieces of stone have been found in the same places as the bones of Homo habilis.
This creature had a lightly built braincase which measured 500-700 cubic centimeters. The second important step saw the appearance of Homo erectus dated to 1.8 to 1.6 million years ago. Homo erectus means an erect or upright man. Its skull was strongly built, its braincase measuring 800-1200 cubic centimeters.
New types of stone tools have been found with Homo erectus. The hand axe is considered the most distinctive. It is believed that the Homo erectus people discovered how to make and use fire, and this kept them warm in cold climates and protected them from wild animals. In sharp contrast to the Homo habilis, the Homo erectus travelled long distances. Their remains have been found not only in Africa but also in China, South Asia, and Southeast Asia.
The third step marked the emergence of Homo sapiens, which means wise man. Our own species evolved from Homo sapiens. It resembles the Neanderthal man found in western Germany around 230,000-30,000 years ago. It had a short body and very narrow forehead, but its braincase measured about 1200 to 1800 cubic centimeters. The race probably evolved in Europe, but the Neanderthal remains have also been found in the Near East and elsewhere in the Old World.
The full-fledged modern man called Homo sapiens sapiens is traceable to about 115,000 years ago in southern Africa in the late Stone Age called the Upper Palaeolithic. Compared to other hominid species, it had a large forehead and thinner bones.
Modern man originally made diverse stone tools for different functions, but it is not clear whether he was anatomically equipped to speak. Till recent times it was thought that language originated around 35,000 BC but now this date has been pushed back to 50,000 BC. However, the Homo sapiens sapiens had a large rounded braincase of about 1200-2000 cubic centimetres in volume. This enabled the modern human to function much more effectively and enabled him to modify the environment.