.... I have submitted a mathematical model of Brahminhood in my post "Are you a Brahmin?"
First it was "No Brahmin - No Tamil", and now "Are you a Brahmin?", nice going.
Such narcissistic preoccupation with Brahminhood is unique to only Brahmins and it is an indicator of supremacist feelings. No NB goes about examining who is a real Shudra, only Brahmins do that.
In any case, the answer to this question is not at all complex, it is as straight forward as who your biological parents are. In theory and in practice as far back as collective memory will go, birth is the only criterion that is used to determine who a Brahmin is, nothing more, nothing less.
In theory, all Brahmins trace their ancestry via birth alone back to early Brahmin rishees who in turn trace their origin to the Brahmin of all Brahmins, Chaturmukha Brhmma. As if to answer any inconvenient questions that may arise, we are told we are not supposed to look for the origins of rishees and rivers.
But in practice it is all a #@^& shoot, who wielded political and economic power determined which varna a clan or tribe belonged to -- Happy has furnished mountains of evidence for this in the past. Before anyone pounces on me that this is a contradiction, the reality is changes happened off and on and Bramins permitted others to become Brahmins based on political and economical convenience, and then clamped the birth rule after that.
People who cite Srimath BG to claim Brahminhood is based on guna have just not understood BG, or the commentaries written by revered acharyas of Brahminical traditions like Adi Sankara, Ramanuja et al. You look at what Arjuna says in Chapter 2, or what Lord Sri Krishna says in Chapter 9, and the commentaries of these verses, there is no ambiguity, birth alone determines who a Brahmin is. The story of Gauthama and Satyakama Jabala is another clear cut illustration of birth determining who a Brahmin is.
Further, if you look at the keepers of Brahmin orthodoxy today, those who come close to performing the rituals mandated for Brahmins, they emphatically state birth alone determines whether one is a Brahmin or not.
So, to bring in guna in this equation as though even one born a Dalit, like Thiruppanazhvar or Thirunalaippovar, can be considered a Brahmin based on their gunas is complete obfuscation of reality and a perverted attempt to usurp all sublime qualities to Brahmins alone. This is what Brahmin supremacists attitude is all about, and the reason why around 97% of Tamils oppose Brhaminism.
Cheers!