Final answer:
Thespis is traditionally credited as the first actor to step out from the chorus and speak solo lines, introducing character dialogues and shaping the foundation of Greek tragedy around 534 BCE. This marked the beginning of a transition from simpler dithyrambic verse to more structured dramatic narratives.
Step-by-step explanation:
According to tradition, the very first actor to step out of the ranks of the chorus and speak solo lines in the year 534 BCE was named Thespis. This event is considered to mark the transition from dithyrambic verse to the more complex form of drama known as tragedy. Thespis introduced character speeches and dialogue, interacting with the choragus, which paved the way for future developments in Greek theatre. The chorus, which originated from Dionysian rituals, continued to play a significant narrative role even as individual characters began to emerge.
Aeschylus later expanded on Thespis's innovation by adding a second actor and reducing the chorus's size, thus emphasizing dialogue and further developing the structure of tragedy. This evolution continued with playwrights like Sophocles, who introduced additional actors and enhanced the theatrical experience with scene-painting and more complex plots.