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The mysterious Moai statues of Easter Island have gazed inland for hundreds of years.

And now experts believe they have finally discovered how the Rapa Nui people placed distinctive 'hats' made of red stone on top of some of the figures' heads, more than 700 years ago.

They believe that the hats, or 'pukao', were rolled up ramps to reach the top of the figures which measure up to 40ft (12 metres) tall.

Mystery solved? Experts believe they have finally discovered how the Rapa Nui people placed distinctive hats made of red stone on top of some of the Easter Island figures' heads, more than 700 years ago

Despite the size of the statues, Sean Hixon an undergraduate student in archaeology and geology at the University of Oregon, believes the rolling of the bulky stones would have been relatively easy. 

'It seems like a relatively small number of people could have done it, either by levering or rolling,' he told the 80th Annual Meeting of the Society for American Archaeology.

This is despite the largest pukaos measuring six-and-a-half feet (two metres) in diameter and weighing 12 tonnes (1,890 stone).

Some 1,000 carved Moai line the perimeter of the 12 mile (25km) volcanic island, which is the most isolated inhabited landmass on Earth with just 6,000 residents. 

A tall order: Physicists believe that the pukao, or 'hats,' were rolled up ramps to reach the top of the figures (examples are pictured left and right), some of which measure up to 40 ft (12 metres) tall

Remote: Some 1,000 carved Moai line the perimeter of the 12 mile (25km) volcanic island, which is the most isolated inhabited landmass on Earth with just 6,000 residents

The island is half the size of the Isle of Wight, or twice the size of Manhattan, and lies 2,236 miles (3,600km) west of the South American mainland.

Since Europeans came to Easter Island, or Rapa Nui, in the 1700s, people have wondered how the vast carved stones were erected, complete with their 'hats'.

Some experts believe the stones were walked into place, while others have suggested that locals chopped down trees to roll the statues into position, unwittingly destroying the forests and causing their own demise through lack of natural resources.

An estimated 100 pukao have been discovered so far, either in place on the statues, or scattered nearby.

They are made from red volcanic rock called scoria and experts are divided as to what they may have been, with suggestions ranging from hairstyles to turbans and diadems.

Despite this, many agree that the red colour of the stone indicates that the pukao had ritual significance.

Mr Hixon's team used basic physics to model the force and torque required to place a pukao on a Moai's head, using different techniques.

These included rolling a 'hat' up a ramp, building a tower, using a pulley system and putting the 'hat' on the statue before raising the whole statue as one.

They concluded that the rounded oblong shape of the pukao means that it would have required relatively little energy to roll them up a ramp. 

A tour or the extremely remote but inhabited Easter Island

Standing guard: An estimated 100 pukao have been discovered so far, either in place on the statues or scattered nearby. This map shows the location of the 887 statues, which gaze inland across the island, with an average height of 13ft (four metres)

It may have been possible for less than 10 men to roll a 'hat' into place, because the oblong shape stopped it easily rolling down the ramp again, but was still a good shape for being hauled upwards.

Some of the statues have indentations which may have stopped them tipping over during placement of the pukao.

And a number of the 'hats also have vertical marks and ring-shaped indentations on their side, which may indicate that strips of wood were used to provide traction up the ramp.

However, while the team thinks ramps were the most likely method for the placing of the hats, their models revealed that any of the proposed methods for raising the pukao would have been possible - with enough manpower.

Erosion and damage have also scarred the sides of the pukao, meaning that analysis of marks and scratches is 'far from conclusive'. 

EASTER ISLAND STATUES MAY HAVE BEEN 'WALKED' INTO PLACE 

It is not known exactly how the vast Easter Island statues came to line the perimeter of the small island.

But in 2013, scientists claimed they may have been walked into position.

A team led by Archaeologists Carl Lipo from the University of California State University Long Beach, and Terry Hunt of the University of Hawaii claimed the statues' bases were carved so they could lean forward to make them easier to transport.

Walk the walk: A team of experts created a five-tonne replica of one of the statues and moved it into an upright position on a dirt path in Hawaii, to prove that the statues could have been 'walked' into place

The researchers illustrated the theory by creating a five-tonne replica of one of the statues and moving it into an upright position on a dirt path in Hawaii.

With just a few ropes, a team of 18 people could rock the statue back and forth, each time inching the statue on just a little bit more. The mode of transport would have taken about two weeks.

The bases would then have been flattened to stand the statues upright once they reached position.

Mr Lipo said the findings may help dismantle the traditional story line of Easter Island, or Rapa Nui, that a 'crazed maniacal group destroyed their environment,' by cutting down trees to transport gigantic statues.

Previous studies have suggested that a lost civilization chopped down trees on the island, laid the statues prone and rolled them into place using logs.