Background: Aesop ( EE-sop; Greek: Aisopos, Aisopos; c. 620 - 564 BCE) was a Greek fabulist and storyteller credited with a number of fables now collectively known as Aesop's Fables. Although his existence remains unclear and no writings by him survive, numerous tales credited to him were gathered across the centuries and in many languages in a storytelling tradition that continues to this day. Many of the tales are characterized by animals and inanimate objects that speak, solve problems, and generally have human characteristics.
Context: The name of Aesop is as widely known as any that has come down from Graeco-Roman antiquity [yet] it is far from certain whether a historical Aesop ever existed ... in the latter part of the fifth century something like a coherent Aesop legend appears, and Samos seems to be its home. The earliest Greek sources, including Aristotle, indicate that Aesop was born around 620 BCE in Thrace at a site on the Black Sea coast which would later become the city Mesembria. A number of later writers from the Roman imperial period (including Phaedrus, who adapted the fables into Latin) say that he was born in Phrygia. The 3rd-century poet Callimachus called him "Aesop of Sardis," and the later writer Maximus of Tyre called him "the sage of Lydia." From Aristotle and Herodotus we learn that Aesop was a slave in Samos and that his masters were first a man named Xanthus and then a man named Iadmon; that he must eventually have been freed, because he argued as an advocate for a wealthy Samian; and that he met his end in the city of Delphi. Plutarch tells us that Aesop had come to Delphi on a diplomatic mission from King Croesus of Lydia, that he insulted the Delphians, was sentenced to death on a trumped-up charge of temple theft, and was thrown from a cliff (after which the Delphians suffered pestilence and famine). Before this fatal episode, Aesop met with Periander of Corinth, where Plutarch has him dining with the Seven Sages of Greece, sitting beside his friend Solon, whom he had met in Sardis. (Leslie Kurke suggests that Aesop himself "was a popular contender for inclusion" in the list of Seven Sages.) Problems of chronological reconciliation dating the death of Aesop and the reign of Croesus led the Aesop scholar (and compiler of the Perry Index) Ben Edwin Perry in 1965 to conclude that "everything in the ancient testimony about Aesop that pertains to his associations with either Croesus or with any of the so-called Seven Wise Men of Greece must be reckoned as literary fiction," and Perry likewise dismissed Aesop's death in Delphi as legendary; but subsequent research has established that a possible diplomatic mission for Croesus and a visit to Periander "are consistent with the year of Aesop's death." Still problematic is the story by Phaedrus which has Aesop in Athens, telling the fable of the frogs who asked for a king, during the reign of Peisistratos, which occurred decades after the presumed date of Aesop's death.
Question: Was he a slave his whole life?

Answer:
he must eventually have been freed, because he argued as an advocate for a wealthy Samian; and that he met his end in the city of Delphi.