I got this link about Atri Smriti from the net.
http://vedicreserve.mum.edu/smriti/11Atri_Smriti.pdf
Perhaps you could go through the pdf and tell me where your cited para appears. I could not find it. Or maybe there is another source? All I could see was that the verse you have quoted is referenced widely in the internet.
Next is that notwithstanding the genuineness of the verse, it seems to have delved into the deepest graves of the vedic people. I do not recollect this system being followed in Ramayana where during Sita Kalyanam, the lineage of both the kings are given !! A kshatriya begets a kshatriya, a brahmana begets a brahmana, a vysya begets a vysya, a shudra begets a shudra - this was how it was/is.
Next is the Mahabharatha where we find Karna possessing qualities of a Kshatriya (in fact he is) but we find everyone scorning him as a soota putra. I do not see the great Krishna himself who supposedly gave the Bhagavad Gita, addressing the public that qualities define the varna, and hence Karna is a Kshatriya.
Please step down from your lofty thoughts about the varna system.
There is nothing to step down because they are not my thoughts. They are my understanding of our scriptures.
What is lofty or not is your judgement based on your background.
Let me quote the reference you asked for, primarily so that the original intent of the thread can get back to its objectives.
Before that let me clarify a few points:
1. For topics involving understanding knowledge-scriptures historical analysis is not useful. If there is an assertion of a timeless truth then that truth need to be available for understanding today. The verse I quoted is subject to understanding if one truly understands the difference between the Sanskrit words Varna and Kula.
2. The confusion of usage of terms Brhamana, Kshatriya, Vaishya, Sudra etc have to be
understood in context whether they refer to Kula or Varna . Your examples refer to Kula definition of these terms
3. The ongoing confusion of these two terms has caused enormous issues in the society of recent past including today and hence clarity here is critical
B.Gita is considered to teach the essence of Upanishads though it is s Smriti. What Sri Sankara has done is to refer to verses from various Upanishads so that the teachings are connected to truths asserted in Upanishads.
These truths are subject to understanding here and now and not for just referring to a verse and declaring that it is right because it is said so in B. Gita.
To do justice to properly explain the verse and varana reference will require 10 hours or more of lecture time to do justice even with my relatively minimal knowledge. I am saying this only to communicate the depth of preparation and effort needed to properly understand these verses. This forum is not a practical means to communicate all that. One does not have to take my word but they have to put in the time to discover this for themselves.
Here all I want to do is cite the verse to show Varna is not connected to birth.
चातुर्वर्ण्यं मया सृष्टं गुणकर्मविभागशः ।तस्य कर्तारमपि मां विद्ध्यकर्तारमव्ययम् ॥ ४-१३॥
Simple translation: The world created by me has four Varnas (groups) divided according to qualities (Guna) and actions (Karma).
Even though I am the creator, know me to be an eternal non-doer.
Here is a reference for another translation :
http://www.bhagavad-gita.org/Gita/verse-04-13.html
There is no mention of Janma in this definition of Varna.
I hope we can get back to the original intent of this thread!