Back on Rapa Nui - Sunday 11 August 2013

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I'm back on Rapa Nui - so I'm restarting this blog. Many people enjoyed the blog when we were on the island to begin the project, so perhaps you will enjoy a burst of new posts, and then sporadic posts describing what we found … and what we still don't know.

Mark Horrocks and I have arrived back to the island trying to settle a few loose ends. Our work to date has been fairly successful. Mark has taken the lead publishing many of our findings, highlighting his ability to identify microfossils showing which depths in our cores show fossil evidence of starch grains and photoliths, and therefore indicate arrival of polynesian crops. 

When combined with soil nitrogen studies (including nitrogen isotopes in the soil cores we sampled), the evidence in our lake and soil cores shows that polynesian agriculture was extensive. We have some questions to resolve about the timeline of agriculture, as we work toward publishing our findings.

I'd like to frame today's post by thinking about the long stream of researchers who have been attracted to the mysteries of Rapa Nui and Pacific migration. This area has a long and famous history. You'll remember that we focussed heavily on testing Jared Diamond's Collapse to design our project. 
Today, I'd like to focus on Thor Hyerdahl's Kon-Tiki. Hyerdahl is famous for sailing from Peru to Eastern Polynesia on balsawood raft, called Kon-Tiki and constructed using known South American techniques, to prove that it was possible for Polynesia to be settled from Peru. 

I've converged on Kon-Tiki as an example for two reasons. First, to help mark the march of time I found my Grandfather's 35 cent copy of Kon-Tiki (pictured) neatly on an old shelf of 1950's Reader's Digests. As I was finishing it on the way to Rapa Nui via Chile, I also noticed that movie called Kon-Tiki was also available on the plane - but it wasn't much good after reading the book. So Kon-Tiki is too much to pass up, and here's why.

Imagine being a researcher trying to understand Pacific migration at the time of Heyerdahl's adventure in 1947. Libby was just inventing radiocarbon dating. So scholarly evidence of the march of time relied on descriptive tools such as the passing of human generations in oral history, and the styles of artefacts such as pottery. With the help of radiocarbon dating and similar methods to precisely calibrate time in any location, Heyerdahl's fascinating idea of eastward migration has now clearly been overwritten by the archeological evidence of westward expansion. First, Western Polynesia was settled at the time of Lapita culture (3000 years ago), and then Eastern Polynesia (e.g., the Society Islands) and finally the far corners of the Polynesian Triangle - Hawaii, New Zealand and Rapa Nui. Recent work led by New Zealander Janet Wilmhurst has focused on compiling a large database and then using only the most reliable radiocarbon dates to identify the time of Polynesian settlements in Polynesia. She shows that all three corners of the Polynesian Triangle were settled right around 800 years ago. What a difference 60 years of research has made. The archaeology of Pacific migration is clear. However, some of the same mysteries that Heyerdahl sought to solve still remain. Evidence emerging from DNA and microfossils continue to provide tantalising evidence of east-west exchanges of people and agricultural organisms. Heyerdahl also argued that exchanges of art and culture accompanied the kumara (sweet potato) on an eastward course.

Certainly, Heyerdahl's thesis has been disproven if it is all or nothing. But the archeological understanding of westward migration leaves some mysteries, largely in the apparent dispersal of organisms between South America and Polynesia. As evidence of east-to-west exchange continues to emerge, perhaps we can solve some mysteries by taking a step back and looking somewhere between Kon-Tiki's script and today's headlines. The raft Kon-Tiki was able to steer eastward, but was unable to tack against the wind, even if someone fell overboard. In contrast, recent headlines remind us that the Polynesian double-hulled sailing waka technology has been revived, and now proven its ability to sail easily from New Zealand to the other corners of the Polynesian triangle. The remarkable reconstruction and demonstration of Polynesian sailing should remind us in 2013, much as Heyerdahl's voyage overturned the desks of academic naysayers in 1947, that Polynesian voyages of discovery and exploration were entirely feasible.

In other words, understanding Polynesian's true sailing ability may change our understanding of the evidence we're looking for, and our willingness as scientists to accept it. Brief visits won't leave much enduring archaeological evidence; and so far, there remains no verifiable scientific evidence of arrival and settlement in the corners of the Polynesian triangle substantially earlier than 1200 AD. But exploratory or trading waka visited a place, it is entirely sensible that they may leave organisms behind, and with observable fossil evidence through pollen, starch grains, or phytolyths. Do we see hints of this?

The goal of our project is to understand the dynamics and magnitude of "Collapse", if indeed a collapse occurred. To do so, we need to put evidence on a timescale and need to think about how to scientifically evaluate and further test evidence that could show the early arrival of organisms but not necessarily imply settlement. And so we are here again, thinking hard. As we attempt to draw our project to a close, it is very interesting to think about how much understanding can change over 60 years, as it has since Kon-Tiki was published in 1950.