Here, came the conquerors

Agriculture was accompanied by domestication of animals. Animals helped, not only in ploughing but also provided milk, wool, skin and other products which were treated by early humans as luxury. It can be argued that domestication of milk giving animals preceded agriculture as there is no clear differentiation. But this can be pointed out that domestication of milk giving animals started in the areas where agriculture was tough or non-existent. Animals were already been domesticated for their meat but as humans realized that they can also get milk from these animals, they started keeping these animals at one place. Pigs and fowls were the first animals to be domesticated for meat. Goats followed with cows and buffalos. Horses, camels and elephants were late entrants. But before all these, dogs were the first animals which were domesticated for help in hunting. Dogs were the natural partners to humans as hunter. Cats and other pet animals became habitual to living with humans very late. Cats, as one of the best hunters, initially scarred humans as they were competitors in hunting and became part of many legends. Other animals also had their share of mystrey. Small cats became as for their stealthy nature were good at stealing food from human storages. Initial food storage also faces the problems of rats and small pests. It is argued that agriculture evolved rapidly only when humans had discovered to store grains in closed tanks or containers.
Domestication of horses was one of the biggest factors which transformed early human society completely. Before horses, human were dependent on only their legs for transportation. As for biological constraints, it limited human group's movements and thus limited interactions between different societies. In the circumstances, most of the human societies developed independently and had completely distinct beliefs, customs, social structure and culture. Competitions between adjoining societies were common but this struggle never spread to a particular region, limited by geographical boundaries. Natural habitat for horses is grass plains and they lived in herds. Humans most probably also used to hunt them but might have soon realized that they could also ride them. Domestication of horses had taken a long time as these animals are not so tame like pigs or cows. Also, riding a horse requires certain skills which also had taken a long time to develop. Once the humans were on top of horses, they started spreading rapidly. First human society which domesticated horses is known as 'Aryans'.
Aryans were mainly hunters and used to have huge herds of cows with them for food. Cow was considered sacred as they used to drink cow's milk which was compared to mother's milk. They used to do their most of the property transaction in means of either cows or horses. They were wanderers and kept moving. As being good hunters, they were also great warriors. With the added advantage of fast riding horses, 'Aryans' dominated most of the other societies whom they came in contact. At the time of 'Aryans', agriculture had transformed other societies and there were many human settlements. Aryans in their ride trounced these societies and destroyed their settlement. Commonalities between most of the languages of Asia and Europe are evidence of Aryans' dominance in their time. When Aryans started their victory march, there were many well developed societies existing, like in India, Sumer, Egypt and Mesopotamia. Chinese society was guarded by high Himalayan peaks thus didn't come in the influence of Aryan invasion. India was the first one to face Aryan’s onslaught. Aryans pushed aboriginal Indians further in Indian peninsula and destroyed their cities. Aryans then moved to west and slowly reached Mesopotamia and Sumer. Sumer was razed and Mesopotamia survived with little remains. Egyptians also faced Aryan brunt and were pushed westwards. Aryans then moved north and dissipated. Influence of Aryan society was so strong that even after many years; these regions were occupied with wars and brutal destruction.