Morals are arbitrary rules of conduct voted into existence by the popular majority of any given society. Oftentimes, they are deployed by a single dictator or monarch. They are also determined by the outcome of civil war or by violent protest. The outcome of the moral compass that a society ultimately lays down is then enforced by said society thus infusing the belief that morals are absolute. These morals that they value will shift over time depending on the makeup of opinions doing the voting, doing the dictating or doing the warring. Morals are a human construction that varies by Time, Geography and Circumstance. All of the morals we value today will someday become "outdated" by a future society that no longer feels the same way.
Thus, morals are rules generated by the consensus of like-minded individuals. It evolves over time as the structure of the social network evolves. It does not "improve" or "degrade" over time - it simply changes based upon the shifting desires of a given social system. Morals do not exist in some aether of matter nor does it exist in the stars or the trees. It also does not exist when a human being is alone. It only emerges when humans form a group. Thus, morals are not imbedded within us. It is entirely a social phenomenon.
Today, most of those wildly different social spheres have largely dissappeared - replaced by a more or less globalized moral system whose societies are now wholly interconnected through vast trade agreements and international resolutions through the United Nations Security Council and the General Assembly.
What kind of morals would you have if you were born some 2500 years ago, into the legendary tribes of the Mayans?
Would you have the morals of a 21st century American even though *America* was not yet discovered and shaped through decades of protests, rallies and a full blown civil war? Would you have been born in the Wrong Place... at the Wrong Time?
Moral relativism however, does not mean there are no morals at all. Moral relativism states that there ARE morals which are created by each society independently from one another - from different locations to different times.
American morals for example are decided by the popular vote of the American citizens - hashing out our differences on the streets, at rallies, at city conferences and in congress. Sometimes they are hashed out in civil wars - like the one Lincoln fought for. Chinese morals on the other hand, are hashed out quite a bit differently from ours where only a small percentage of the population decide what is right and what is wrong. These rights and wrongs that all societies build independently are then enforced by each society on their own thus causing each to believe that they have the moral superiority.
Morals are not only relative by location but are also relative by time. A hundred years ago in America, introduction of same-sex marriage bills would get you lynched by a mob like the KKK. Today, its sweeping the nation because the society that is now doing the voting is comprised of people who feel very differently from the society that existed 100 years ago.