Applying to only one lab per university, good or bad?

[LongGraduatedStudent]

If there is only one professor at a a given institution that you are interested in working under, should you apply for only that one professor or should you include professors doing different things that are somewhat (but not absolutely) related? I have begun work on my Penn State and CUNY applications and have noticed they ask me to list 1-4 professors.

So far I have only contacted one faculty member at each university I plan to apply to, and I am not clear on how I would contact an "alternate professor". I've email eight professors at eight universities. I've got replies from six; five said they are looking for grad students and one said they might be (and asked for a CV and GRE scores). Of the two that haven't responded, one is practically retired (which is a bummer because he was one of my top choices) and the other is apparently on leave.

I know that I shouldn't tailor my statement of purpose to be focused completely on molecular anthropology, but it also shouldn't be extremely broad either because there will be multiple physical anthropologists (and probably archaeologists as well) on my admission committee.

[anthropologygeek]

One is fine. All that means is your app goes directly to them and if they say no they won't waste other Profs time.