With only scanty evidence for burial customs, and none for skull types, the ethnology of North-Eastern Greece cannot rest on a firm basis. We have seen, however, that there is a great general resemblance in culture between Thessaly and Thrace and the regions beyond. Therefore it seems highly probable that the main element in the population of North-Eastern Greece in prehistoric times had Thracian connections. From time to time this stock was doubtless strengthened by fresh incursions from the north, and in this probably lies the explanation of the appearance of spiral decoration in the Second Period. Thus we may accept Tsundas' Thracian theory in a general sense without admitting the validity of all his arguments. It seems, for example, fantastic to call in Thracians to explain the occurrence of stray figurines of a northern type at Sparta. Their early date by itself puts them probably outside the range of tradition, and similarly the suggestion that the legend of Tereus, and the Thracian war against the Minyae is based on events that took place in the First (Neolithic) Period is incredible. The tales of Thracians in Phocis and Boeotia must belong to a much later period, though probably there was always a certain Thracian element in the population of those districts.

Owing to the legends that connect Pelasgians with Thessaly, Tsundas considers that they also formed a large part of the population, and he makes them mainly responsible for the introduction of spiral decoration.