I would posit that there is in fact a definitive morality (in terms of defining "right" and "wrong") for the human species, and they come almost entirely from a biological/evolutionary source. As we evolved, generally the humans that cooperated and refrained from putting the self above the whole survived better than those who focused solely on the self. This gave rise to the basics of morality, which every culture and society I've ever heard of shares (being that murder, theft, etc committed against a member of the society is wrong).
There are certainly more... refined, for lack of a better word, aspects of morality that vary by culture, but the core principles are universal throughout (successful) human history. It's a biological fact that the average human is predisposed to be repulsed by the concept of murder, torture, and the like.
And before anyone raises the point, sociopaths and the like are simply another evolutionary path of the human mind. It came about because if there is a small minority of people who abuse the trust of the rest, they can successfully come out ahead. However, if the whole behaves in that fashion, it renders their most powerful, and necessary, tools null and void.
Edit: On a side note, none of this applies to any other sentient species. They will have followed an entirely separate evolutionary path, and thus cannot be expected to have the same biological/cultural inhibitions. I guess, in a way, there is no real "universal" morality that applies to all beings, in all places, and at all times, but there almost certainly is within the human species.