(i) The Mesolithic period, also referred to as the Middle Stone Age, witnessed environmental changes like the melting of glaciers and their replacement by thick forests.
(ii) This period stretches from 12,000 years ago till about 10,000 years ago.
(iii) The people of this period used small tools called microliths, such as spearheads and arrow heads.
(iv) Probably, agriculture was also practiced to some extent.
(v) Domestication of animals, most importantly of dogs, started.

The major developments of the Neolithic age are :
(i) Growing crops and domesticating animals.
(ii) Use of polished stone tools and weapons.
(iii) The art of making pottery and making painted potteries.
(iv) Practice of the burying the dead along with pottery, weapon, food and drink.
(v) Invention of the wheel.

The reasons behind the movement moving of hunters-gatherers are:
(i) If they stayed at one place for a long time, they would have eaten up all the available plant and animal resources. Therefore, they had to move elsewhere in search of food.
(ii) Animals move from place to place - either in search of smaller prey or in the case of deer and wild cattle, in search of grass and leaves. That is why, those who hunted them had to follow their movements.
(iii) Plants and trees bear fruit in different seasons. So, people may have moved from season to season in search of different kinds of plants.
(iv) People, plants and animals need water to survive. People living on river banks had to go in search of water during the dry seasons as some rivers are seasonal while others are perennial (with water throughout the year).

(i) The tools (A) were used for:
1.grinding the grains.  
2.making of tools.
(ii) The tools (B) were used for:
1.cutting meat.
2.chopping fruits.
(iii) The tools (C) were used for:
1.digging soil.
(iv) The tools (D) were used for:
1.hunting animals.
(v) The tools (E) were natural pebbles which were also used for:
1. grinding grains.

There were major changes in the climate of the world. Climate became relatively warm than the past. This warm condition led to some major changes:
(i) There was development of grasslands in many areas. As a result, the number of animals, which survived on grass, was increased. These animals were deer, antelope, goat, sheep and cattle.
(ii) This increasing number of animals helped people to start thinking about herding and rearing of these animals. Fishing became important.
(iii) At that time, several grains bearing grasses like wheat, barley, rice grew naturally and men became aware about where these grew and when they ripened. These grains were collected by men, women and children and they started thinking about growing these plants on their own.

Stone tools found during the Mesolithic period are called Microliths. They were generally tiny in size. The Mesolithic man probably stuck these stones on to the handles of bones or wood to make tools such as saws and sickles. These tools were used for digging the ground and stitching clothes.