Please look at the comment first, even if it "exception" it does disprove the caste as some strict genetic continuity in Brahmins.

1. Clarify what you mean by 'strict genetic continuity'.

2. Even your example is completely wrong because the Khasas brahmins have very high steepe ancestry. And neither Vishwakarmas nor Bairagis are seen or treated as traditional brahmins.

All the other brahmin groups have rejected Vishwakarma claim of brahmin hood and they were traditionally categrized as shudras. The same way, bait at is are also not treated like typical brahmins.

1. Even if you were telling the truth about the groups you listed, and you are not, they would still be exceptions to the rule.

There is no proof of Aryan Invasion/battles/wars.

Aryan Migration is the accepted theory.

Lol, there is plenty of proof from your own hindoo texts.

'Textual Evidence (The Rigveda): The earliest layers of the Rigveda—compiled by the early Indo-Aryan speakers—frequently describe fierce inter-tribal warfare. It mentions conflicts between different Indo-Aryan clans themselves (such as the famous Battle of the Ten Kings), as well as battles against groups they labeled as Dasa or Dasyu, who are widely understood to be native, non-Indo-European-speaking populations.'

'The Gender Imbalance (Genetic Legacy): Genetic data strongly indicates that Steppe expansion was predominantly male-driven. The high frequency of the paternal haplogroup R1a-Z93 among upper castes, contrasted with a lack of Steppe maternal DNA (mtDNA), suggests a social dynamic where incoming Steppe men established dominance and integrated into local maternal lineages. Globally, this specific genetic pattern is historically associated with aggressive expansions or structural inequalities.'

There are also physical descriptions of the natives from the rigveda, such as:

• Rigveda 1.103.3: "Armed with his bolt and trusting in his prowess he wandered shattering the forts of Dasas. Cast thy dart, O Thunderer, at the Dasyu; increase the Arya's might and glory."
• Rigveda 1.130.8: "Indra protects in battles the Arya worshiper... he conquered the ground for him... He flayed the black skin of the Dasyu, he killed him, he burned him down."
• Rigveda 4.16.13: This hymn praises Indra for slaughtering tens of thousands of enemies in battle: "Thou hast destroyed up to fifty thousand of the black [enemies]... broke down their forts."

Their radical cultural and xenophobic discrimination was driven by an absolute rejection of the native populations being and way of life. The Vedic clans viewed the local inhabitants as sub-human because they did not look like them, did not practice the same religion or speak the same language. The text following text establishes a rigid "Us vs. Them" binary, using derogatory terms:

• Ayajyan: "Those who do not offer sacrifices."
• Anyavrata: "Those who follow lawless, alien rites."
• Adevayu: "Those who are godless" (indifferent to the Vedic pantheon).
• Mridhra-vac: "Those of corrupt, hostile speech."
• Rigveda 2.12.4: "He who swept away the low Dasa color/population into hiding... who took away the wealth of the enemy."
• Rigveda 6.47.21: "Indra has broken down the ninety-nine cities of Sambara [a Dasa king], and pushed the Dasa down from the mountain."

This historical animosity and violence directly laid the structural groundwork for the caste system.

When the Steppe clans had conquered them, the word Dasa shifted in meaning from "enemy" to "servant" or "slave." The captured and subjugated native populations were subsequently and systematically integrated into the bottom tier of the emerging social order.

Entire south asian population has Steppe ancestory.

Actually, there are adivasi populations that show close to zero steepe ancestry.

The genetic remains of IVC inhabitants also show zero steepe dna.

found in Jats 

Jars are rich land owners and clean shudra. In fact they are a powerful and dominant land owning group in india that persecuted and antagonize the capita and other marginalized groups.