It is the question addressed in this column by Professor Michael Boylan, and his answer is that there are. He sets out the case for them at some length, giving different possible variants (interest theories and agency theories); and leaving aside for the moment a particular way in which he expresses the argument, I'm with Boylan. I think it is indeed meaningful and true to speak of universal human rights - irrespective of culture. This doesn't mean that every culture recognizes all the rights that can validly be claimed as being human rights. But calling them natural is a way of saying, precisely, that they are universal entitlements whether recognized by particular cultures and governments or not. The moral case for them is derived from the 'conditions... necessary to ensure minimal well-being', or from those indispensable requirements for guaranteeing healthy human agency, as Boylan explains.
My one reservation about the way he makes the case is his talking in places about human rights 'existing', as if their status might be comparable to the status of such entities as rocks or rivers or clouds. But human rights are norms, and without human beings would not exist. Even if this doesn't render them culturally relative, since they can be derived from features of the human make-up that are quite general, it does mean that they require a form of imperative (alongside those universal human needs) to sustain them. Boylan writes:
If it is true that there is a logical, objective, concrete basis for human rights that is not tied to time or place, then such an argument would be sufficient to show that there are natural human rights.
Indeed so. While the objectivity of that basis, however, is real enough - located in the physiology and mentality of human beings - the imperative to attend to the requirements for human flourishing, or to avoid what makes people suffer needlessly, isn't based logically on anything else. It's a kind of fundamental (or 'ground') norm, one that happens to be very widely subscribed to, for obvious reasons, across our species - and that, or so it strikes me, is good enough. The value that is a human right needs valuers to make it what it is.