The changing cycles of climate and weather have greatly affected the human evolution to a very large extent. The last 6 to 8 million years have generally seen cooling trends marked by recurring ice ages. The onset of the ice age around 2.5 million years ago covered most parts of Earth with snow and there were major changes in climate and vegetation.
The species which could adapt better to the climatic changes and procure food survived and the others became extinct. The ice age or glacial age-induced the early humans to wear animal skins to keep themselves warm. Many times, new species originated, which adapted better than the earlier ones.
The early species Australopithecus faced gradual extinction and genus **** (early man) which was better adapted to drier conditions survived. The last ice age witnessed by earth was about 20,000 years ago. Today, we are living in a time that is relatively warm compared to the last 6 to 8 million years. The weather and climate of the earth has played an important role in the origin, evolution, and existence of various species.
Human species evolved larger and complex brains to overcome the environmental challenges and survive against physically powerful animals. The size of the brain in the habilis was 600 cubic centimeters, which was only slightly larger than that of Chimpanzees. The erectus had a brain size of 800 – 1100 cc, the Neanderthal 1200-1900 cc and the **** sapiens (wise man) of today about 1400cc.
It is more than twice the size of the brains of Chimpanzees or Gorillas. The growth in the brain size induced many activities like improved vision, upright posture, bipedalism, toolmaking, use of ****, planned and skilled hunting, storing food and language.
These activities helped in the development of the brain. Hominoids lived on trees which provided them protection from the predators. The Hominoids were food gatherers and not meat-eaters. Then, they adapted to land-dwelling. They began to use caves and extended stone boulders as shelters.
The Neanderthal man was the earliest cave dweller. The shortage of food made them to scavenge for food. The above activities made them gradually develop an upright posture and consequently the bipedal motion. This was required for survival.
Hominines and the archaic human species added planned hunting and fishing to the already existing gathering, foraging, and scavenging techniques. The earliest evidence of planned hunting and butchery of large animals is traced to two sites.
Box grove in England dated to about 50,0000 years ago.
Schoningen in Germany dated to about 4,00,000 years ago.
The Hominoids were quadrupeds. They walked on all four limbs, but, their forelimbs were flexible. The Hominids gradually adapted an upright posture. Hominines further adapted to bipedalism. The skeletal structure and the muscles also adjusted over a ** of time to the upright posture and the bipedal motion, which freed the forelimbs.
The forelimbs developed precision grip and power grip and evolved into hands. This greatly helped in hunting and defending from predators as hands could be used to make tools and also use them. Walking on two legs also provided a greater long-distance vision and helped them to cover long distances without spending much energy.
The use of tools is not confined to only humans. For e.g. some monkeys and apes use stones as tools to break nuts. But use of tools by humans is far more advanced compared to the monkeys and apes. Wood, bones, and stones were used to make tools. They were mainly used for hunting or defending from predators. The use of stone tools is studied as the Stone Age in history.
The making and use of stones tools were responsible for the evolution of forelimbs into hands and also the growth in brain size. As planned hunting required co-operation and communication between the hunters, signaling and creating sounds evolved, which slowly developed into languages. The domestication of animals and the commencement of agriculture were other major factors in the human evolution.
