Archive for April 15th, 2013

Programming note

Monday, April 15th, 2013

The blog is on the move again. We’re switching to a new host with unlimited bandwidth because two bandwidth exceeded shutdowns in three months is more than I can tolerate. The data transfer will begin shortly. Any comments posted after the transfer has begun may be lost, so steel yourself.

Once the content has moved, DNS propagation might make the site unavailable for as long as 48 hours depending on where you are. In my experience, it has never taken anything close to that much time, but forewarned is forearmed and all that.

Whatever happens, don’t freak out. It’ll all be cool in the end. :cool:

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Digital imaging reveals history of moai carvings

Monday, April 15th, 2013

Researchers at the University of Southampton have used digital imaging to examine in greater detail the carvings on the back of Hoa Hakananai’a, an Easter Island statue in the British Museum. Eight feet high with the oversized head, prominent eyebrow ridge, long nose, longer ears and downturned mouth characteristic of the moai (meaning “statue” in the Rapa Nui language), this particular specimen some unusual features. Most of the moai — 834 out 887 — were carved out of tuff, a soft volcanic stone that is easily carved. This is one of only 13 that was made of hard basalt, a much more difficult material to carve, which suggests this statue was commissioned by someone of wealth and rank. Its body was once painted in red and white, but all the paint was lost during the long ocean voyage from Easter Island to England in 1868.

The back of the statue is covered in intricate ceremonial imagery connected to the birdman cult, a religion that grew on the island starting around 1400. Hoa Hakananai’a was made around 1000-1200 A.D., so those carvings were added hundreds of years later. By the 17th century with the culture under pressure from ecological disaster, the ascendance of the birdman seems to have come at the expense of the moai and the traditional ancestor worship that generated them. The monoliths began to be toppled. There were still some standing when Captain James Cook crew arrived in 1774 — a landscape painted by William Hodges, Cook’s artist, depicts several standing moai wearing their red stone hats — but only a few. The last report of upright statues came in 1838. When Hoa Hakananai’a was removed from Rapa Nui in 1868, there were none left standing.

In the transitional period between the moai and the birdman, at least some of the old statues were carved with symbolism from the upstart cult. The soft tuff statues were easily eroded, so little evidence remains on their bodies. The carvings on the basalt statues, therefore, are important sources of information about the profound cultural changes on Easter Island from the 15th century onward. Yet, they have not been thoroughly studied by archaeologists, not even Hoa Hakananai’a who has been sitting in the British Museum for 145 years.

Imaging technology can help bridge that knowledge gap. The University of Southampton researchers deployed photogrammetric modelling, wherein an object is photographed hundreds of times from different angles to create a composite digital model that can be viewed in 360 degrees, and reflectance transformation imaging which takes hundreds of high resolution pictures under different angled lights to illuminate details with light and shadow, a far more agile digital version of an analog archaeological practice done with flashlights and head tilts.

Using these techniques, Mike Pitts and the team made some fascinating discoveries, perhaps the most significant being the apparently simple recognition that a carved bird beak is short and round, not long and pointed as previously described: this allowed the two birdmen on the back to be marked as male and female, unlocking a narrative story to the whole composition relating to Easter Island’s unique birdman cult. They also realised that the statue is one of the few on Easter Island that did not stand on a platform beside the shore. It is now believed to have always stood in the ground, where it was found, on top of a 300 metre cliff.

Mike comments: “Study of the tapering base suggests that rather than being the result of thinning to make it fit into a pit, as often suggested, it is more likely part of the original boulder or outcrop from which it was carved. This may also explain why, as we now see it in the British Museum, it appears to lean slightly to the left – its uneven end resulted in its being incorrectly set into its 19th century plinth.”

There are several phases of carving on the back, separated by centuries. The carving around the waist of three bands is a maro, a symbolic loincloth which, along with the ring just above it, were part of the original design. Later, once it was half-buried in debris, four komari, inverted V shapes representing female genitalia, were carved from top to bottom on the back of the right ear.

Even later than that, the central story of the birdman — a male fledgling with an open beak reaching out of the nest while two birdmen with the head of a bird and human hands and feet stand watch on either side of him — was carved on the back. The human-bird hybrid on the right has a rounded beak, indicating femaleness. That suggests the two birdmen are actually the chick’s mom and dad. Underscoring the gendering of the birdmen, the female is on the side of the komari, while the male is flanked by a carving of a ceremonial dance paddle called an ‘ao, a symbol of male authority.

The digital imaging has also revealed a rounded shape near the bottom half of the female birdman which could be the egg the fledgling has just hatched from, and the remains of what may have been fingers around the statue’s navel that were later removed.

Creating digital models of such complex surfaces is a complex process. The project is ongoing, so the team hopes to reveal even more details as they continue to work on it.

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