When was the first history of slaves?
The first documented history of slaves would most likely be ancient Egypt since it is part of their hieroglyphics dipicting the slaves that build the pyramids of Egypt. Slavery as been around since ancient civilizations and is apart of our human history. Since it would not be completely certain, its hard to say what is the very first documented history of slavery, so generally you can note that it was apart of ancient civilizations such as Egypt.
Slavery has been documented as early as 9000 B.C. when anthropologists unearthed remains in southern Africa in which a group of pygmies were shackled together. In ancient Babylonia, King Hammurabi's code includes specific guidelines concerning the treatment of slaves. Egyptian hieroglyphics also detail the enslaving of other human beings.
I tend to believe that slavery is as old as mankind itself. In all kinds of animals living in groups, the practice of the dominant member of the group imposing restriction on freedom on other members of the groups. In some, the practice of actual slavery exist, where insect of one species invade and enslave all members of a group of similar, but slightly different, species. Knowing the selfish nature of humans and existence of practice of slavery even in other living beings with much lower level of development, it is not difficult to believe that slavery among humans is as old as the mankind.
Definite indications and proofs of slavery since ancient times are available through several sources. The first well known case of slavery practiced by civilized people is provided by Sumerians in Mesopotamia. In this civilization, the slaves formed the lowest class of society about 3500 B.C.