Obviously beauty is not limited to just one ethnic group, but subjectively people do have their preferences. My preference for males is African/African-American and Native-American. My preference for females (because I'm an equal opportunity lover, lol) is Irish.
That being said, I've dated within several different ethnicities and don't put one above another because it is not their ethnicity that makes me interested in dating them. I just find that physically I am attracted more often than not to the above listed ethnicities, but physical attraction only is lust, not love. 
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