Polynesian voyaging driven by resource shortages

 A lot of the research into Polynesian voyaging looks at how it was accomplished and when, but less work has been done on why.

Why would groups of individuals, living in Pacific paradise islands, expend enormous treasure and energy to build great canoes and outfit massive voyaging missions?

The answers are coming.

This blog first looked into the issue in 2007.

That article reviewed a paper that suggested that sea level changes between 4,000 and 6,000 years ago, which created resource shortages, could have launched the Polynesians eastward into the Pacific from the islands near Asia.

And now, there’s new research that suggests a second period of resource shortages 1,000 years ago drove the final exploration phase—the one that led to the inhabitation of Hawai’i, Tahiti, the Marquesas, the Cooks, and eventually Rapa Nui and Aotearoa.

The suggestion is that a huge, multi-century central Pacific drought, from about AD 900 to 1200 drove settled populations out of the central Pacific and led them to locate new homelands that could feed expanding populations.

A team of Hawai’i, United Kingdom and New Zealand researchers in 2020 published a paper saying the signs of that drought can still be located in lake sediments in the Pacific Islands.

Their work answers that nagging question about Pacific voyaging: Why? Why would islanders in rich environments expend vast resources to build and provision voyaging canoes, and then sail into the uncharted ocean?

The paper’s authors are David A. Sear, Melinda S. Allen, Jonathan D. Hassall, Ashley E. Maloney, Peter G. Langdon, Alex E. Morrison, Andrew C. G. Henderson, Helen Mackay, Ian W. Croudace, Charlotte Clarke, Julian P. Sachs, Georgiana Macdonald, Richard C. Chiverrell, Melanie J. Leng, L. M. Cisneros-Dozal, Thierry Fonville, and Emma Pearson. Morrison is a senior archaeologist with Honolulu’s International Archaeology, LLC.

Their research paper, “Human settlement of East Polynesia earlier, incremental, and coincident with prolonged South Pacific drought,” was published in 2020 in the Proceedings of the National Academy of Sciences.

That prolonged drought was detected in sediments in Efate in Vanuatu, ‘Upolu in Samoa, and Atiu in the Southern Cook Islands. Other data from Tahiti and Kiribati also supports the drought hypothesis. It lasted from about AD 900 to AD 1200.

Their suggestion is that exploratory voyagers sailed out initially around 900, that they located islands and brought that information home, but that actual colonization took place generations later.

But once again, the message is that Polynesians voyaged because they had do.

© Jan TenBruggencate 2024

Biological control for Coconut Rhinoceros Beetles?

 Researchers across the world are looking for some kind of bug or disease that can control the coconut rhinoceros beetle, (CRB).

Beetle infestations elsewhere were controlled a few decades ago with the release of a biocontrol virus called Oryctes rhinoceros nudivirus. But in Hawai’i we have a new strain of CRB that seems to be resistant to that virus.

Hawai’i’s biotype of the beetle, also found in Guam and some other Pacific areas, is called CRB-G (clade 1.)

As scientists scramble to look for predators, parasites or disease that might help, research is now focusing on a fungus called Metarhizium, which, when it is effective, kills the CRB beetle larvae and then covers the beetle larva with white fuzzy hairs that later turn green.

There is still more work to be done, but “biopesticides containing Metarhizium spp. are the strongest candidates for inundative biological control against the emerging CRB threat,” said this paper, which will be published in the November 2024 issue of the journal Fungal Biology.

 (Adult CRB, image courtesy Hawaii Department of Agriculture)

That work is being done by researchers from Papua New Guinea, the Solomon Islands, Colombia, and New Zealand, and was funded by the New Zealand Ministry of Foreign Affairs and Trade.  The lead author of that paper is biocontrol researcher Laura Villamizar of AgResearch Ltd. in New Zealand.

One particular isolate of one species of the fungus, Metarhizium majus, appeared to kill CRB (S and G haplotypes) larvae within three to four weeks of application.

“Under field conditions, this isolate demonstrated its ability to infect CRB, dispersal up to 100 m from treated artificial breeding sites, and persistence in soil for at least four months,” the authors said.

That’s all good, but it is early research, and before a biocontrol can be released into a new environment, work needs to be done on what the unwanted impacts might be…like, does this fungus also attack the larvae of valued pollinating insects? 

 

 (Larval CRB, image courtesy Hawaii Department of Agriculture)

Meanwhile, we are approaching the infestation with conventional means.

This giant horned beetle is devastating Hawaiian coconut palms and threatens many other species. Entire coastal palm landscapes on O’ahu, where the beetle was first spotted in 2013, have been destroyed. The creature is actively spreading on other islands, having been identified on Kaua’i, Maui and Hawai’i islands.

The website of Coconut Rhinoceros Beetle Response has extensive information on the threat.

https://www.crbhawaii.org/

The beetle is known commonly as CRB, and science calls it Oryctes rhinoceros. The armored adult is up to two inches long and bores into the hearts of palms to feed on their forming leaves. The beetle larvae are the size of your thumb, and feed on decomposing plant debris—characteristically in compost and debris piles.

In addition to coconuts, they will go after other palms, including the threatened native loulu fan palms, as well as bananas, hala, kalo and sugar cane. Even some hardwood trees have been targeted.

Infected coconut palms are easily recognized by the jagged vee-shaped cuts in their fronds, caused by the feeding beetles when the fronds are still forming.

 (Adult CRB. Note the horn. For more info see https://dlnr.hawaii.gov/hisc/info/invasive-species-profiles/coconut-rhinoceros-beetle/. Image courtesy Hawaii Invasive Species Council.)

Control measures have include putting netting around the palms to block beetle entrance, and using insecticides. But for many palms and in many environments, neither is a feasible solution. (Some of the palms are too tall to realistically treat.) Furthermore, some insecticides can render the coconuts inedible.

Using attractants like pheromones in traps has been another approach. Here is a paper on the pheromone research done on the beetles. https://www.sciencedirect.com/science/article/pii/S0261219423002235

You will see pheromone-infused hanging insect traps at various locations around the affected islands.

 Here’s a trap system folks have used in Guam. https://www.youtube.com/watch?v=47ZQddcvFHk

There is a product called Palm Tree Weevil Killer, PTWK, which claims to be a non-toxic treatment that will kill beetles in the tree. We have not seen independent tests of this system and how well it works. Here are a couple of links: Link 1, Link 2. https://www.hawaiipalmguard.com/uploads/b/58101110-0675-11ef-8f26-0d8569411a43/d9f82fe0-1094-11ef-b96b-3ffeb1dc7cd9.pdf

https://www.alohatreesavers.com/our-product

© Jan TenBruggencate 2024

 

Voyaging: Nailing down when the first canoe pulled up on a Hawaiian beach.

 

Your grandfather might tell you otherwise, but it is increasingly clear that the first humans set foot in Hawai’i in the year AD 1000, give or take a few decades.

Archaeologists and other researchers have been honing on that period for a couple of decades as their tools have improved for determining the age of human-related activities and artifacts. Early, widely varying carbon-14 dates have been adjusted and refined, and several new technologies have been added to the tool kit.

This isn’t brand new information, but I still hear older Hawai’i people advocating for dates they remember being taught as little as 30 or 40 years ago.

Until and into the 1980s, the common assumption was that the Hawaiian Islands were first inhabited early in the first millennium after Christ, and a few folks still still argue for AD 500, 300 or occasionally even earlier.

In his seminal 1985 book Feathered Gods and Fishhooks, leading Pacific archaeologist Patrick Kirch reflected the wisdom of the period: “It is clear that colonization parties from the Marquesas were responsible for the settlement of Easter Island by about A.D. 400 and of Hawai’i by possibly by A.D. 300.”

But the science has improved much since then, and the errors of the early dating have been corrected. By the 2023 revision of Feathered Gods and Fishhooks, Kirch and Mark McCoy had moved the number to closer to 1000.

Why? Wrote the authors: “No one could have foreseen…the major technological advances that would come…the use of GPS and GIS in settlement archaeology, AMS radiocarbon dating and Bayesian modeling…high-precision dating of corals, stable isotope analysis of faunal remains or XRF geochemical analysis of stone artifacts.”

Professional archaeology now assumes there weren’t any humans in the eastern Pacific as early as CE 300 or 400. (Maybe a lost fisherman or an intrepid sailor who left no evidence.) It is more likely that Polynesian voyaging canoes around AD 900 began pushing—probably from the Samoa islands—into eastern Polynesia.

Why did those Polynesians voyage? There have been many theories, but one recent one is that they were driven out of their home islands by drought. David Sear and co-authors Melinda Allen, Jonathan Hassall and Emma Pearson said that drought may have lasted 200-400 years, certainly from before AD 900 to after 1100. 

Whether or not drought alone was enough to coerce people to abandon their homes, there’s an associated stressor. Population pressure would have been a big factor as expanding island families began outgrowing their small islands’ ability to feed them.

Science now generally presumes that on departure from the central Pacific islands, some of the eastern Pacific islands south of the Equator were populated first. Perhaps the Cook Islands, which are just to the southeast and downwind of Samoa. Then the nearby islands and finally then canoes came north to Hawai’i, east to Rapa Nui (Easter Island) and then west to Aotearoa (New Zealand.) The chronology could change with additional findings and new technologies.

But all of that voyaging may have occurred in a pulse of only a few generations. The voyaging canoes left Samoa around 900 and would have populated all those other islands within just a couple of hundred years.

“The archaeological and paleoenvironmental estimates of the colonization date show a striking convergence, indicating that initial settlement (of Hawai’i) occurred at A.D. 940–1130…and most probably between A.D. 1000 to 1100,” wrote pollen expert Stephen Athens and Timothy M. Rieth and Thomas S. Dye, in a 2017 article in the journal American Antiquity, entitled, “A Paleoenvironmental and Archaeological Model-Based Age Estimate for the Colonization of Hawai’i.” 

They cited updated radiocarbon dating and pollen from archaeological coring data.

One of the best resources for dating first human activity on Kaua’i was developed by David Burney and William “Pila” Kikuchi at Makauwahi Cave on the swampy south coast of the island. Their 2006 paper, based on flooded sediments in the cave floor, estimated first Polynesian activity at between AD 1039-1241. 

A lot of the earliest archaeological dates in Hawai'i are now settling in on that time period.

What is amazing, given the compressed period of Hawaiian occupation, is the extent of the great public works that were completed: the many hundreds of fishponds, the massive stone temples, the remarkable waterworks for flooded kalo fields and the vast dryland field agricultural systems.

© Jan TenBruggencate