The history of slavery covers many different forms of human exploitation across many cultures throughout history. Slavery, generally defined, refers to a situation where one human being is considered to be the property of another, and is therefore obligated to perform tasks for their owner without any choice involved. It can be traced back to the earliest records, such as the Code of Hammurabi (ca.
1760 BC), which refers to it as an established institution. Slavery in ancient cultures was known to occur in civilizations as old as Sumer, and it was found in every civilization, including Ancient Egypt, the Akkadian Empire, Assyria, Ancient Greece Rome and parts of its empire. Such institutions were a mixture of debt-slavery, punishment for crime, the enslavement of prisoners of war, child abandonment, and the birth of slave children to slaves.
In the Roman Empire, probably over 25% of the empire's population, and 30 to 40% of the population of Italy was enslaved. Records of slavery in Ancient Greece go as far back as Mycenaean Greece. It is often said that the Greeks as well as philosophers such as Aristotle accepted the theory of natural slavery i.e. that some men are slaves by nature.
At the time Plato and Socrates slavery was so accepted by the Greeks (including philosophers) that few people indeed protested it as an institution , although there were in fact a few voices of opposition[citation needed]. During the 8th and the 7th centuries BC, in the course of the two Messenian Wars the Spartans reduced an entire population to a pseudo-slavery called helotry. According to Herodotus (IX, 28–29), helots were seven times as numerous as Spartans.
In some Ancient Greek city states about 30% of the population consisted of slaves, but paid and slave labor seem to have been equally important Greeks however were among the first Europeans to abolish slavery with their constitution on 1823, which specifically noted that "in greek territory no human being can be sold or bought, no matter his or her religion, and if a slave enters Greece, he is automatically considered an absolutely free man or woman and nobody can make claims on him or her".