Caste doesn't fall under any of these. Because people are clearly willing to hire Hindu people born in India of any gender. So you aren't discriminating against race, national origins, religion, color, or gender. Since the USA doesn't acknowledge caste it can't differentiate between two people of different caste just because of their caste.
The only thing you mentioned that might apply is "Ancestry" but I can't find a description of it since it isn't listed under the protected classes list.
Discrimination isn't inherently illegal. For example, you totally can discriminate against people under the age of 40. Which does happen. Many landlords won't rent to people under 30 and that's perfectly legal.