Hello,

Are you enquiring about having anthropology as an optional paper in UPSC exam with BA in political science? If yes, then it's absolutely fine as long as you fare well in Prelims, and qualify Mains with good marks, everything is going to be all right, no need to worry about these things, so many engineering students have qualified UPSC with a totally different aspirant, one such I can remember is a topper with engineering background taking up philosophy as an optional, see the interview process in UPSC is going to be an analysis of your entire personality, your traits of being an able administer, how aware you're of existing situations and your ability to deal with the same, this is not a knowledge  test, I mean yes you'll be asked about latest happening so do continue reading newspaper till the day of interview, but it isn't limited to this. So, don't worry, as long as you can do well, it's all fine, the only advantage of having a graduation subject as optional paper is candidates are already acquainted with the subject, hence the preparation process becomes easy, but to each his own, if you can manage it then go ahead.