Herodotus was one of the earliest authors to engage in this form of interpretation. In his observations regarding the Egyptians, he establishes Greco-Egyptian equivalents that endured into the Hellenistic era, including Amon/Zeus, Osiris/Dionysus, and Ptah/Hephaestus. In his observations regarding the Scythians, he equates their queen of the gods, Tabiti, to Hestia,
Papaios and Api to Zeus and Gaia respectively, and Argimpasa to Aphrodite Urania, whilst also claiming that the Scythians worshipped equivalents to Herakles and Ares, but which he doesn't name.
Some pairs of Greek and Roman gods, such as Zeus and Jupiter, are thought to derive from a common Indo-European archetype (Dyeus as the supreme sky god), and thus exhibit shared functions by nature. Others required more expansive theological and poetic efforts: though both Ares and Mars are war gods, Ares was a relatively minor figure in Greek religious practice and deprecated by the poets, while Mars was a father of the Roman people and a central figure of archaic Roman religion.
Some deities dating to Rome's oldest religious stratum, such as Janus and Terminus, had no Greek equivalent. Other Greek divine figures, most notably Apollo, were adopted directly into Roman culture, but underwent a distinctly Roman development, as when Augustus made Apollo one of his patron deities. In the early period, Etruscan culture played an intermediary role in transmitting Greek myth and religion to the Romans, as evidenced in the linguistic transformation of Greek Heracles to Etruscan Her[e]cle to Roman Hercules.