A 12-METRE monolith, hacked out of limestone by stone-age humans some nine thousand years ago, has been found at the bottom of the Mediterranean.

The enormous stone totem, now split in two and sitting in the Sicilian Channel between Tunisia and Sicily, was hewed from a rocky outcrop some 300m away when the Mediterranean Sea was still a dry basin.

It’s now under 40m of water.

The new study, published in the Journal of Archaeological Science, says the area was submerged about 9350 years ago (give or take 200 years) when the last Ice Age retreated. Before that time the area was believed to be something of an archipelago, with a string of islands linking Europe to North Africa via a shallow sea.

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“It was cut and extracted as a single stone from the outer rectilinear ridge situated about 300 to the south, and then transported and possibly erected,” the study reads. ”From the size of the monolith, we may presume that it weighs about 15 tons.”

The researchers say the existence of the monolith — which features unusual holes drilled through its base — is forcing scholars to rethink the technological know-how of ‘primitive’ hunter gatherers.

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“This discovery provides evidence for a significant Mesolithic human activity in the Sicilian Channel region,” the research paper reads.

Sicily, now an island off Italy, is believed to have been settled between 17,000 and 27,000 years ago when there was a land bridge linking it to the Italian mainland.

Principal authors Emanuele Lodolo and Zvi Ben-Abraham say evidence the stone block was man-made and not a natural anomaly include its regular shape, and three similar-sized holes.

Manufacturing, moving and erecting a monolith of such size required careful cutting work, extraction techniques and transportation. Such skills had not been previously associated with such an ancient people, the study says.

“The discovery of the submerged site in the Sicilian Channel may significantly expand our knowledge of the earliest civilisations in the Mediterranean basin and our views on technological innovation and development achieved by the Mesolithic inhabitants.”

The nearby island of Malta is home to a series of mysterious megalithic temples. These have been tentatively dated to some 5600 years ago.

The oldest known structure is at Gobekli Tepe, in south-eastern Turkey. Carbon dating places the hewed stone structures — including 200 pillars weighing up to 20 tons — to be about 11,600 years old.