Here are the most probable hypotheses about the origin and spread of the four mentioned populations:
1) The Pheleset (represented in Egyptian hieroglyphs with plumed hats) are probably identifiable with the Pelasgian. This pre-Greek population was partially submitted and partially confined by Greeks to peripheral zones (Arcadia, Thessaly, part of Crete, some Cyclades islands, the Aegean coast of Anatolia). At that age, it was completely absorbed by the Mycenaean civilization. Cretans/Minoans might be considered as Pelasgians, too. This circumstance might explain the links that the Philistine from Palestine had with Crete (viz. the “Book of Amos”, etc.). The introduction of the Greek-Mycenaean language in Crete from approximately 1425 B.C. might explain the disappearance of the substantive Keftiu (Cretans) in the Egyptians inscriptions as well as its substitution with the generic indication “Populations from the Sea and Islands”, in order to define them as Greek-Mycenaean speaking. It is commonly accepted that Pheleset settled, as Philistines, into the land that is still today called Palestine from them. Their presence is demonstrated by the local production of Mycenaean III C ceramics (1200-1050 B.C.), which is, however, common to the other Sea Populations too.
The legendary Pelasgian (therefore, “Philistine”) foundation of some localities in the Italian peninsula (Adria, Pisa, Saturnia, Sutri, Agylla/Cerveteri, Palo/Alsium and perhaps also Pirgy/Santa Severa and Metapontum) it is still waiting for a demonstration. Nevertheless, Pelasgians could have left clues such as the manufacture of III C Mycenaean ceramics at the Delta of the River Po (Frattesina and Fondo Paviani), at Termitito (MT) and Broglio di Trebisacce (CS). It is worth to mention also the presence of imported ceramics on the Tolfa Mounts (Monte Rovello, San Giovenale, Luni sul Mignone). One cannot exclude a small Philistine migration into Sardinia, already reached by the Cretans/Minoans in previous age as documented by the style of the ingots of Sardinian copper as well as their marking with letters of the Minoan alphabet. Indeed, a limited percentage of the Sardinian miniaturized bronze statuettes, “bronzetti”, (approximately 15%) has plumed cap. Even the depiction of the hero Sardus Pater has a plumed cap.

2) The origin of Shardanas, mercenaries for excellence, is uncertain. Still to verify is the hypothesis concerning their origin from the city and hinterland of Sardi (Western Anatolia/Lydia). According to Garbini, the force balance within the Sea Populations assigned to the Shardanas the northern Palestinian territory. Later on, Shardanas might have leagued with the Israelites, constituting the tribe of Zabulon, one of the twelve Biblical tribes.
The Shardanas horned headgear, corsage and sword are identical for style to those of the chieftains of Sardinian tribes, as depicted in the local miniaturized bronze statuettes. This undoubtedly indicates Sardinia as their final landing-place, after a period of stay (variable from some decades until to a pair of centuries) in Palestine.
Warriors with the same hat and armament are indicated as navy invaders on Corsican menhirs. This fact documents the emigration of a consistent part of Shardanas into Sardinia. It is also to mention the homonymy of two denominations: Shardana (the oriental population) and Sardinia (the Island of Tyrrhenian Sea). Local made Mycenean III c ceramics have been recovered at Sarroch (CA).

3) The archaeologists are carrying to light possibly Sheklesh villages in the Syrian-Palestinian corridor, at Dor and Tell Zeror. A subsequent Sheklesh emigration to Sicily, parallel to the Shardanas one to Sardinia, and the identification of this population with the Sicels would be proved by the recovery at Monte Dessueri (SR) of amphoras which are identical to those from the necropolis (11th century) of Azor, near Jaffa. In the same period (1050-850 B.C.), the civilization of Cassibile or Pantalica II (SR) blossomed in Eastern Sicily. In the island, the Mycenaean and Cypriot presence is attested during the previous century by the fortified coastal village of Thapsos (SR), that seems to have been destroyed just about 1200 B.C., and the spread of the Pantalica I culture (1270-1050 B.C.), with III C Mycenean ceramics.
The Eastern Mediterranean origin of Sicels contrasts with some traditions that indicate them as immigrants into Sicily from Central-southern Italy (from Latium). It cannot be excluded, however, that some isolate groups of Sicels, arriving from Orient, may have reached the peninsular coasts too (as Pelasgians did). It might have caused the misunderstanding of a presumed emigration from the Italian continent to Sicily. The historians asserting this point, in fact, claim the “Sicel” foundation of some Latium cities (Fescennium, Faleria - before the Pelasgians conquer- Coenina, Crustumerium and Antemnae). The Sheklesh might have forged the bronze tripod, cauldron and wheel discovered in fragments at Piediluco (TR). They might also have made some 12th century “Aegean-oriental” potshards recovered at Campo of Santa Susanna (RI) and III C Mycenaean ceramics unearthed at Termitito (MT) and Broglio di Trebisacce (CS).

4) The Tyrsh (Teresh, or Tursha), plumed cap represented, might to be identified with a Semite population from the hinterland of Tarsus (Cilicia). They were partially Mycaeneanized, too. Biblical and ancient historical Greek narrations (Herodotus at first) indicate them as colonizers
of a mythical western land: the legendary Tarshish or Tartessos, rich in silver mines and flowed by the homonymous river.
This land fits Western Sardinia well, being the centre of the richest silver deposit of the Mediterranean See (Argentiera/SS). Here there are the Tirso River and, in archaic ages, the Semitic colony of Tharros. Herodotus narrates that the population of Tyrsenos, after having emigrated from Lydia (Asia Minor) due to famine and “passed many populations”, finally arrived to a land flowed by a sea that, from their name, was called Tyrrhenian Sea.
As mentioned above, a small percentage (approximately 15%) of Sardinian mignon bronze statuettes wears the Tyrsh plumed cap.
The plumed cap is worn also by the Sardus Pater and Baal, the main Phoenicians God. Therefore, it cannot be excluded a substantial identity of the Tyrsh/Tyrsenos/Tartessos with the first Phoenician settlers of South-Western Sardinia, preceding the Carthaginian conquest.

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Several clues convey to assert that there was no discontinuity between the Mycenaean frequentation of Italian coasts and seas, the stabilization of consisting nuclei of Sea Populations into Sardinia, Sicily and some peninsular localities, and the subsequent Phoenician and Greek colonisations. According to this point of view, also the external solution of the Etruscan riddle might be not so far.