According to one school of thought, the present day Brahmins are the descendents of Aryans who invaded India from central Asia around 6000 B.C, settled in the Gangetic plain and established their way of life, after driving out the local inhabitants called the Dravidians, to the South. Aryan society was initially divided into three classes, the priestly class, the warrior class and the rest. Over the millenniums intermixture took place and the Dravidian priestly class adopted the Brahmin norms of the conquerors.

Yet another school of thought that has gained ground in recent times, challenges the Aryan invasion theory as a biased view of Western Indologists, albeit their commendable contributions in collecting analyzing and spreading the message of the Vedas. Not denying that people from central Asia might have come to India, as have several successive waves, this hypothesis says that a highly evolved culture already existed which assimilated the Aryans. This view is supported by archeological findings at Harappa (now in Pakistan). This period is recognized as the Indus (Sindhu river) valley civilization.

The earliest reference to Brahmins, a derivative of the word Brahmana, in the classical language of Sanskrit, occurs in the Vedas written about 6000 B.C

" Brahmanosya mukhamaseeth
 bahoo raajanya kritaha
 Uroo tadasya yadVysyaha
  Padbhyagam shoodro ajaayata." (Purusha Sukta)

‘Brahmins represent the face of the creator,
 warrior class (Kshatriyas)  the shoulders,
 merchant class (Vysya) the thighs and
 the agriculturist class (Shudra), the legs.’ 

In the Bhagavadgita, which is of much later origin, lord Krishna says,

" Chaatur varnam maya sristyam, Guna, Karma vibhagashah".

‘ I created the four classes, depending on their nature (Gunas namely Satva, Rajas or Tamas) and past actions (Karma).

 The scriptures do not say that this class is superior  or that class is inferior. Heredity as a caste marker is of much later origin and thousands of castes have proliferated in India.

From ancient times  Brahmins are dedicated to the study of the Vedas, Philosophy, Teaching, Astrology and Medical science, spreading the message of Hinduism, being advisers to kings and Governments and so forth.

In answering his own rhetorical question ‘ What is the duty of the Brahmin?’ The sixty – eighth Shankaracharya of the Kanchi Kamakoti Peetham, has said, ‘ The most important aspect of our worldly lives is to obtain the grace of God. It is the duty of the Brahmins to obtain such grace for the benefit of society’.