Caste system is an inborn quality of
DRAVIDIAN PEOPLE not aryan's. 
 [please argue with me here]
[see how Maraimalai adikal also thought like this]

During Tamil Sangam Periods, you see many people's -poets caste name along with their original names.

Valluvan is still a SC caste in india. They are Astrologers by caste. From which the Great Tamil Saint Thiru Valluvar born, converted to Saakiya Madham - Samana Madham - the Jains. Yes Valluvar is a Jain!.

I think it is adopted, modified, poisoned as a Tool by Aryans to promote their Life and Times.

Dravidian Caste System was not rigid. It accepted Evolution from Low Caste to High Caste.

Aryan Caste System replaced this with Rigid System. That's where problems started.

The Tamil Saying, Kallarum, maravarum mella mella maruvi vellalar ayinaare! says it all.

In India, still today people escape from the Casteism's clutches by running to other states, places, change their caste name to a more socially acceptable one, then feign as a Brahmin or some other FC.

Even in some cases accepted Sex happens between castes to promote them to better caste.
Example:- Nair/Menons supposedly used Nambodhiris help to copulate the new bride.
So, nothing is permanent, nothing is rigid.

Today in Hindu Newspaper or Daily Thanthi newspaper we see lots of "NEW CASTES" born every week. Chera Nattu Pillai, Tirunelveli Aiyar, Sri Rangam Aiyangar, Sivakasi Nadar, Virudhunagar Nadar - all these used to denote more safe selection of species, a kind of insurance for knowledgeous or skilled children, social networking, easy climb to top.
 

PILLAI AS A WORK RELATED NAME

"The Post master was universally known as "Anchal Pillai" and was a man of considerable influence"
http://naturemagics.com/kerala_history/kerala_history_pages/interestingsidelights.htm
The above words are found in the Kerala History pages, this makes clear that just like "Mein" symbol of harappan - indus valley writings, this pillai is a common sur name to all castes of Dravidians.
Accounts employee = Kanakku Pillai
Masonry duty = Kothap pillai
Cooking duty = Thavasu pillai
Anchal = postal duty = Anchal Pillai
People who lived in Fort = Kottai pillai
and so on and so forth.
So PILLAI MUST BE A UNIVERSAL CASTE NAME, APPLICABLE TO ALL CASTES OF TAMIL - KERALA NATION TAMIL NADU OR THE DRAVIDA COUNTRY.

MARAIMALAI ADIKAL ALSO THOUGHT LIKE THIS

My above mentioned TITLE, caste system is a unique quality of DRAVIDIANS, not ARYANs, has found support in 1876-1951 by Maraimalai Adigal. Following is his famous treatise "Vellalar Nagarikam"

NOTE: following text of Maraimalai Adikal is taken from ...
http://www.epw.org.in/showArticles.php?root=2005&leaf=05&filename=8711&filetype=html

“In the olden days, when the Vellalas were practising agriculture and expanding civilisation, Aryans were merely leading a hunting and pastoral life. That is why, cultivation had been condemned in the books authored by them (bramins) and their followers. Moreover, the imposition that cultivation should not be performed by anyone belonging to their community could also be found in these books.”

In keeping with their uncivilised status, the religio-moral universe of the Aryan brahmins had also remained unrefined. They worshipped ‘minor’ deities such as Varuna and Indira, offered them inebriating drinks, and persisted in “the performance of bloody sacrifices so much so that as time went on, their conduct became more and more revolting to the delicate feelings of the humanitarian Vellalars.” Even the constant efforts of the Vellalars to initiate the Aryan brahmins into civilisation ended in failure. When the Vellalars disrupted the rituals of blood sacrifices that were periodically carried out by the Aryan brahmins, it enraged them and as a result, they characterised the Vellalars as rakshashas and asuras. Blood sacrifice is thus a sign of the Aryan’s civilisational inadequacy.

“it is the Vellalars who divided the other Tamils, who did not avoid killing [animals] and went low in morals, into 18 [occupational] groups to assist them in cultivation and to do other occupations useful to them.”

“...by avoiding killing and non-vegetarian food and by grounding themselves firmly in [high] morals one can become as elevated as the Vellalar.”

“It is essential that those who follow the Saivite moral of non-meat-eating should mix only with others who also follow the same moral. If they have to mix with meat-eaters…they should do so only after converting them to Saivism…”