The Petralona cave (Greek: Σπήλαιο Πετραλώνων) also Cave of the Red Stones (Greek: Σπήλαιο ” Κόκκινες Πέτρες “), a Karst formation – is located at 300 m (984 ft) above sea-level on the western foot of Mount Katsika, about 1 km (0.62 mi) east of the eponymous village, about 35 km (22 mi) south-east of Thessaloniki city on the Chalkidiki peninsula, Greece. The site came to public attention when in 1960 a fossilized archaic human skull was found. The cave had been discovered accidentally only a year earlier (1959) after erosion had left clefts in the rock. “Bejeweled” with impressive stalactite and stalagmite formations and holding an abundance of fossils, the cave soon attracted geologists and paleontologists. After decades of excavations the cave is open to the public and scientific work is documented and presented in an adjacent archaeological museum.

The cave’s most prominent fossil specimen, since known among paleoanthropologists as the “Petralona Skull”.

The on-site Anthropological Museum of Petralona displays a selection of the cave’s findings.

The cave was discovered accidentally in 1959 by Fillipos Chatzaridis, a local shepherd who was looking for a spring. In his effort to find a water source he found a small cleft on the slopes of Mount Katsika. Two men were lowered down and later described a large number of chambers and corridors, totaling 8 to 10 meters high with rich and beautiful formations of speleothems (stalactites and stalagmites).

The cave developed during the Mesozoic (Jurassic) limestone, its sediments are divided into several stratigraphic levels. “The rock formations resemble giant cactus, pink pearls, sturdy columns or delicate curtains, and in several places water ponds are fed by stalactite material. Covering an area of 10,400 m2 (112,000 sq ft), the length of the corridors is about 2,000 m (6,562 ft) and the temperature throughout the year remains stable at 17 ° C (± 1 º C).” The first research of 1959 was undertaken by the Greek speleologist Ioannis Petrocheilos. He found numerous bones of animals, many of them covered with cave coral.

The Petralona skull according to Aris Poulianos, head of the excavation team since 1965, was found by a villager, Christos Sariannidis, in 1960. It was sticking to the cave wall about 30 cm (12 in) above ground, held by sinter. Its lower jaw is missing and it was “encrusted by brown calcite soon after the death of the individual”

Poulanios (1981) estimated the age of the skull at around 700,000 years. He announced that “the date was based on analyses of the cave’s stratigraphy and the accumulated sediments”.

Poulianos concluded that the skull represented a previously unknown hominin genus, unrelated to Homo erectus, and even outside of Homo, introducing the genus name Archanthropus, and the trinomial Archanthropus europaeus petraloniensis for the Petralona skull itself. Independent paleanthropologists have tended to classify the skull as either Homo erectus, Homo heidelbergensis or Homo neanderthalensis.

Poulianos claims have been a continuing cause of controversy since, his conclusions being in conflict with mainstream models of the speciation of genus Homo and its early dispersal.

Poulianos complained that excavations on the site were delayed and/or had to be discontinued several times, first in 1967 and the following years in relation to the Greek coup d’état, and again in 1983, when the Ministry of Culture declined to re-issue the excavation concession until “in 1997 the Anthropological Association of Greece, after 15 years of trials, was justified by the Supreme Court and was ordered the continuation of its works in the cave.” Poulinaos repeatedly accused the Greek government of conspiring to suppress his discoveries, as in 2012 excavation rights were revoked again.

In 1981, the age of the Petralona skull deduced by Poulianos was investigated and the protocol published in the journal Nature. The scientists involved used electron spin resonance measurements of the calcite encrustation and of bone fragments, and dated the age of the skull to between 240,000 and 160,000 years old.

Poulianos dates the fossil stratigraphically, claiming an age of the relevant layer of about 670,000 years old, also based on electron spin resonance measurements. Other researchers point out, that contextual animal fossils “found with it are known elsewhere from approximately 350,000 years ago”.In 1987 researchers announced that the cranium cannot be older than 620,000 years, based on palaeo-magnetic and mineral magnetic studies of the cave’s sediments.

In 1992 an international team published its results of a uranium-series dating analysis of the small cavern, called “The Mausoleum”, where the skull was allegedly found and the sediments, named “Layer 10” by Poulianos. The results confirm earlier findings “that the whole of layer 10 represents a long time span, from about 160 ka to more than 350 ka”. The minimum age refers to the brown calcite layer, which covered and cemented the hominid skull to the wall. The fossil encrustation is insufficient to date it by alpha-spectrometric, uranium-series methods, yet its minimum age was concluded to be also 160.000 years.

Today, most academics who have analyzed the Petralona remains classify the hominid as Homo erectus. However, the Archanthropus of Petralona has also been classified as a Homo heidelbergensis, Neanderthal (Homo sapiens neanderthalensis) and as an early generic class of Homo sapiens. A. Poulianos, on the other hand, believes that the Petralona cranium is derived from an independent class of hominids unrelated to Homo erectus.

The skull of Petralona. Archaeological Museum of Thessaloniki.
Runnels and van Andel summarise the situation as follows: “The only known hominid fossil in Greece that may be relevant is the Petralona hominid, found by chance in 1960 in a deep cavern in the Chalkidiki. Controversy surrounds the interpretation of this cranium, and it has been variously classified as Homo erectus, as a classic Neanderthal (Homo neanderthalensis), and as an early representative of Homo sapiens in a generalized sense. The consensus among today’s paleoanthropologists is centered around the idea] that the cranium belongs to an archaic hominid distinguished from Homo erectus and both the classic Neanderthals and anatomically modern humans. Whatever the final classification may be, the cranium has been provisionally dated to ca. 200–400 thousand years old and it is thus possible that the Petralona hominid is a representative of the lineage responsible for the Thessalian Lower Paleolithic sites.”

The Anthropological Association of Greece has continued to announce new findings in the cave, such as 4 isolated teeth, then two 800,000 year old pre-human skeletons, and a great number of fossils of various species.

The fossils have been preserved at the Geology School of the Aristotle University of Thessaloniki since 1960.

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