Is there a real morality?

I have been getting into this discussion with a few people lately and no one has been able to change my mind just yet. My position is that there is no unchanging and definite morality (e.g. a set of moral principles that, regardless of time, place, or culture remains unchanged and entirely understood). Rather, I believe that morality is changing and entirely depends on the time, place, culture, and utility. If it were beneficial to allow for murder and it allowed for the smoothest running society then we would have no problem with murder. For a real-world example, it was once perfectly acceptable to treat certain people as no more than equipment or animals to be used for physical labor; today, we understand that all human beings are valuable and should be treated as human beings. What do you believe? Is there an all-encompassing and permanent morality or is it dependent?