In Vedic era a Brahmin was a person who had acquired Self- knowledge or Brahma Gnana Atma Gnana.+

In the Vedic era, a Brahmin was a person who had acquired Self- knowledge or Brahma Gnana Atma Gnana. This was an extremely difficult path of the discipline of body, mind, and intellect, and people irrespective of their birth or class, who were dedicated to such an austere life, were recognized as Brahmins. 

A great example of this tradition (that a person becoming a Brahmin, rather than born as one) is in the case of Vishwamitra, a warrior (Kshatriya), who became a Brahmin after attaining Atma Jnana or Self-Knowledge.

A smritis or code of conduct composed by sage Atri defines brahminhood very clearly:~

"By birth, every man is a Shudra (an ignorant person). Through various types of disciplines (samskaras), he becomes a dwija (twice-born). 

 
Through the studies of the scriptures, he becomes a vipra (or a scholar). Through the realization of a supreme spirit (Brahma jnana), he becomes a Brahmin."

The belief that people born in the Brahmin caste, automatically become Brahmins, is a much later concept in very ancient India. Thus, Brahmin means not the caste, but, one who has attained Atma Jnana or Brahma Jnana. 

Sage Sankara, in Bhaja Govindam, says:~ (Jnana Viheena Sarva Mathena Bajathi na Muktim janma Shatena) - One without knowledge does not obtain liberation even in a hundred births, no matter which religious faith he follows. 
 
Thus, it proves that religion is not the means to self-knowledge or Brahma Gnana or Atma Gnana. : ~ Santthosh Kumaar