Were the Greeks indigenous?

In short, the legends portray Heracles as of the Mycenaean royal family having been born to Alcmene, the wife of Amphitryon, son of Alcaeus, grandson of Perseus, king of Mycenae, although Zeus was his actual father.  The story goes that Heracles may have been the rightful heir to the Mycenaean throne if only he was born before Eurystheus, son of Sthenelus, grandson of Perseus, but Hera delayed the birth of Heracles and Eurytheus was born first.   As an adult, Heracles, in order to atone for the murder of his own family from a fit of insanity caused by Hera was told by the Delphian Oracle to submit to Eurystheus, now king of Mycenae.  The twelve labors the Mycenaean king imposed on him are seen by some as a series of campaigns (Heracles as a general) which first took place about the Argolis, later, throughout the Peloponnese, and the last ones, overseas, in effect to create an empire for the king of Mycenae. 

Afterwards, as a freeman, Hera continued to cause Heracles greater misfortune which caused him to become a slave to the queen of Lydia.  Some view this as Heracles becoming some mercenary general, because of his adventures in western Anatolia.  Eventually he was freed and became a warlord, engaging in piracy and brigandage.  Establishing a base in Arcadia he reaked havoc on the Peloponnese.  Following this, he left the Peloponnese for central Greece for adventures there where he married his final wife, Deianira.  Among his adventures was his aid to the Dorians against the Dryopes.

With the death of Heracles, Eurysthenes the king of Mycenae began the persecution of his children.  The Heraclidae found refuge with the Athenians.  Eurysthenes attacked the Athenians but was defeated, captured and executed.  The Mycenaeans through an oracle chose the Atreidae to rule them.  Having again been denied the rule of Mycenae, the Heraclidae ravaged the Peloponnese but were defeated by Atreus and their leader Hyllus was killed.  They withdrew from the Peloponnese to Dryopis (the later Doris) where the Dorians excepted them as equals.  For the next two generations the Heraclidae led the Dorians into the Peloponese but were defeated each time.  It was in the third generation of Heraclids that they were successful in leading the Dorians into permanent domination of the Peloponnese. 

The ancient myths do in fact speak of wars between Greek kingdoms.  Thebes, itself was destroyed because of a generation-long war with Argos (The Seven Against Thebes, The Epigoni).  It would therefore not be inappropriate to consider the Return of the Heraclidae as an invasion in the truest sense of the word.  The very regions which they came to dominate are in fact the regions which archaeology has shown to have been depopulated.  The Dorians would have pushed populations into the periphery of their power, and the archaeology does in fact show that regions not touched by the Dorian invasion did gain an increase in population, such as Attica and Euboia.  According to the legends, the Achaeans pushed out the Ionians out of the northern Peloponnese and forced them eastwards into Attica.  Since the Dorians supposedly originated from a region in central Greece within the boundaries of Mycenaean culture, it then stands within reason that their culture would not be particularly different from other parts of Greece.  Their passage into the Peloponnese would be relatively undetectable.

Elusive read the below topic how appeared and estimated the Descent or Invasion of Dorians in the Hellenic peninsula

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