The term 'Early Stone Age or Paleolithic Age' was coined by archeologists to distinguish other ages from Stone Age. Paleolithic Age accounts for 2.5 million years of human evolution before today. During that time, humans were grouped in small societies such as bands, gathered plants and hunted wild animals. They used knapped stone tools along with bow and wood tools. The food sources of hunter gatherer humans of the Stone Age included both animal and plants. They ate animal organs like livers, kidneys and brain. Dairy products or carbohydrate rich plant foods like legume or cereal grains were not consumed much. They ate plant roots and leaves. Near the end of the glaciations 15000 to 9000 years ago, mega fauna or large animal species in Asia, Europe, North America and Australia faced extinction possibly due to climate change. The middle Stone Age or Mesolithic Age lasted from the last ice age 10,000 years ago to 6000 years ago. The sea levels rose and finally new food sources became important. The development of Mesolithic tools began in response to these changes. They allowed easy hunting and fishing. The domestication of dog as a hunting companion dates to this time. The Neolithic or new Stone Age is characterized by adoption of agriculture and development of pottery.