Differences in the culture...
The Aryans get their name from the Sanskrit word arya meaning "noble". These light skinned migrants from the steppes of present-day Russia had a unique culture.
The Aryans maintained a militarian society before adapting to the agricultural ways of the Indus River valley people. They worshiped fierce gods and goddesses which reflected the Aryans fighting way of life. The most prominent god worshipped by the Aryans was called Indra.
Their military tactic included using their superior horsemanship and chariots as well as bow and arrows, spears, and axes to conquer surrounding areas. The use of horses provided a distinct military advantage against many other native groups including the Harappa. Unlike many invaders the Aryans did not conquer to spread their culture to the new region but rather to gain wealth in the form of cattle.
This society, although it was constantly changing, demonstrated the basis of the caste system prior to migration into the Indus River Valley region. The Aryan culture was based purely on language not ethnicity.
Changes in Harappan Society...
When Aryans migrated into the Indus River Valley, they remained herders for many years with their cattle benefitting from abundant grazing land. Cattle was one of the new societies greatest productions. They later adopted the beneficial agriculture of the region. Although they adapted to agriculture, they changed many pre-existing aspects of the Harappan Society.
Aryans brought their Sanskrit writing to the areas of the Indus River valley and used it to record significant religious works that had been orally passed down for generations. The passing down of these religious works was the most significant accomplishment of the Aryan people; however, the religion of the Aryans was influenced by the dravidians of the Indus River valley. This religious blend was recorded in the four Vedas.
The Aryans brought the Rig Veda into the Indus region, this new social structure divided society into four levels. These levels were priests, warriors, merchants or artisans, and laborers. People conquered by the Aryans were excluded from the system. These social levels set in place by the Aryans later became the basis of the varnas or levels for the caste system whose influence can still be felt in present day India.
Inside the varnas are the jati or the specific professional roles of a kinship group. These although present before the Aryan migration, became more specific as time wore on. These reflect the views of Hinduism.
Members of the Aryans placed themselves at the highest levels of society. These levels included the Kshatriya, Brahmin, and Vaishya.