The Iliad is an ancient Greek epic poem traditionally attributed to Homer and thought to have been written in the late 9th or 8th century BC. The Iliad is generally thought to be the oldest work of European literature (and indeed amongst its finest) and catalogues events during ten days of the Trojan War; a major theme is the destructive effects of anger.
There is an interesting reference to cheese in Book 5 of the Iliad where on Mount Olympus and on the orders of Zeus, chief of the gods, Paieon (physician to the gods) calms the fury of Ares, the god of war:
"As when fig-juice is added to white milk and rapidly coagulates the liquid, and the milk curdles as it is stirred, so speedy was his healing of raging Ares "
Although the possibility of acid coagulation on addition of the juice of figs cannot be ruled out, this may also be a reference to the rennet coagulation of milk by ficin, a thiol proteinase present in fig latex. Ficin coagulates milk well; we made cheese using this enzyme (and also bromelain from pineapple) some years ago. Although we did not taste the cheeses, the extensive and interesting patterns of proteolysis visible by polyacrylamide gel electrophoresis suggested that the product would have been extremely bitter.
Particularly from references in Roman authors, I get the impression that a wide range of rennets, including many plant rennets, were used in ancient times. Most plant rennets are most unsuitable for cheesemaking as they are far too proteolytic; the only plant rennet that is commonly used today is prepared from the flowers of the cardoon thistle (Cynara cardunculus) and is used in a few artisanal cheeses made on the Iberian peninsula.
Other references to cheese in ancient Greek literature include the mention in the Odyssey (Book 9) of the Cyclops Polyphemus making ewes' milk cheese in "well made dairy vessels" and "pails swimming with whey" (images thoroughly familiar to many cheesemakers throughout the Mediterranean basin today). The Father of History, Herodotus (484-408 BC) refers to "Scythian cheese" and the philosopher Aristotle (384-322 BC) mentions that Phrygian cheese was made from the milk of mares and asses. Unsurprisingly, cheese was also prescribed in the diet of Spartan wrestlers while in training!