And it was hard for me to believe and accept but in realistic day to day world Jaati is by birth. Genetics is next to the God. Nature hardly cares for an IIT/MIT/Harvardian or a school drop out when it comes to survival endurance and longeivity. Life is a practical joke thrown at humanity by God.
Samar, there are flaws in your logic. It seems to me that you are convinced about the segregation of different social groups (caste, ethnicity etc.) according to "superiority-hierarchy" [based on a cocktail of IQ and/or endurance and/or longevity].
I do agree with the fact that nature does not made everybody equal but then within a particular group itself people are unequal. For instance: Taking the above example of IQ, consider two groups
A and
B; If these groups are sufficiently large then IQ value curve will show a significant variation in both groups. Mother Nature dictates the terms here and hence a dumbbell shaped curve.
So for a person from group A, it is
better to choose somebody from the top 10% group B rather than choosing someone from bottom 90% of group B! (speaking academically).
Now arises The Question:
If the "average-A" is superior than the "average-B"? Answer is not that simple. Problem lies with the definition of "superiority". Does being physically strong is enough for superiority? OR IQ also matters OR street-smartness and smugness

are also important for survival?
Then there is problem of external factors (money, family, opportunities, geography, food habits, etc.) which can soooo easily
undermine the
genetics.
You said, genetics is next to God, I would say
external factors are equal to God.. may be more than God.
Suppose,
person X has a fine set of genes (strong IQ, immunity from diseases, etc.);
person y is with 'average' genes but born in a decent (in richness term) family.
Person X works in mine/farm/factory with poor health regulations and
person y is a software engineer and work out regularly. ----> Chances are
person y will live longer (and happier) than
person X.
There goes the whole concept of genetic-superiority.
[btw there is a nice movie Gattaca discussing the question of genetic-superiority & will power]
Okay, I have few questions:
1. Talking about "gifts of knowledge", nobody can beat "Jews". Jewish Nobel Laureates are far far more in number than any other ethnicity/religious group. Goes without saying Nobel Laureates means the he/she is the pioneer of his/her field and he/she has contributed a lot for the betterment of humanity.
Does it mean Jews are "superior" than others? Where does Indians or Jats lie in this hierarchy?
Even in India, if you look at the IITs or NITs or university professors. Bengalis dominates everywhere. Be it TIFR, BARC, CSIR labs, IISc, any IIT, DU dept or colleges, south, north everywhere. Does it mean that we (Jats and other north Indians castes) are dumber than Bengalis ?
2. Physically: Indians are "tiny" as compared to most Europeans. I am sure Jats are not "giant" either when compared to any west or northern Europeans. A look at the average heights will confirm that. one can even see girls above 180 cms in almost all street.

Does this make us any 'inferior'? We are not excelling at sports either (like, Aussies). Are we inferior or Does it has something do with Govt and sports ministry?
3. Life-expectancy: a very simple measure of conventional longevity. Again we (Indians and I am sure Jats too) are 'poorer' than westerners in this aspect. Are we 'inferior' ? or is it because of some "external factors"?
-----
As pointed out by Anjoo,
compatibility is a good enough reason for marrying someone- inter-caste or intra-caste.
If we strictly go by the superiority-index-manuals (if such things exist), most Jatnis will end up marrying Jews or Europeans or Americans or Aussies. And "Genetics" would suggest that it is better to allow polygamy and terminate almost all Indians (among others) as this would make world less prone to diabetics & cardiovascular diseases.
P.S. Evolution is probably the most misquoted concept.