The origin :
The gotra system is part of a system of classification or identification of various Brahmin families in ancient times. The gotra classification took form probably sometime during the Yajur Veda period, after the Rig Veda period. It is believed that the gotras started to consolidate some around 10-8 Century B.C. The present day gotra classification is created from a core of 8 rishis (The Saptha rishis + Agastya). The Seven rishis are Gautama, Bhardwaja, Vishwamitra, Jamadagni, Vasistha, Kashyapa and Atri. Seven Rishis (Saptarshi) are recognized as the mind born sons of the creator Brahma. They desired offspring and received it.

Over the years the number of gotras increased due to:

- Descendents of these Rishis also started new family lineage or new gotras (Kaundinya was a descendent of Vasihta, Vishwamitra was a descendent of Kaushika and Vatsa was a descendent of Jamadagni)

- By inter marriage with other Brahmins

- Inspired by a saint whose name they bear as their own Gotra.

- New groups like Kshatriyas (who were also makers of hymns) were taken into fold by some Rishis

The lines of descent from the major rishis are originally divided into Ganas [sub divisions] and each Gana is further divided into families. However, subsequently the term gotra is frequently applied to the ganas and to the families within the ganas interchangeably.

These Rishis belonged to different sects like Shakti, Shavites and Vishnavites and had different deities for worship. Such deities came to be known as the Kuladevatas.

Importance of Gotras
The gotra system was instituted for the purposes of identifying one's ancestors and pay respects during various invocations and other rituals to honor their fathers, fore-fathers and so on, up to their respective Rishis. This was later extended to other aspects of the Brahmin life, such as Marriage and temple worship. In present days, marriage will not be allowed within the same gotra in order to avoid impure matrimony. This thinking is in tune with the modern day genetic paradigms of hybrid vigor.

Gotras, Surnames and Kuladevatas
The gotra is also interlinked with the Surnames and the Kuladevatas. An illustrative list of Mahawar gotras is given below: