Collapse: How Societies Choose to Fail or Succeed (24 page)

When their number climbed from the original band of 27 settlers in 1790 to 194 descendants in the year 1856, that population overtaxed Pitcairn's agri
cultural potential, and much of the population had to be evacuated by the
British government to distant Norfolk Island.

The remaining habitable island of Southeast Polynesia, Henderson, is
the largest (14 square miles) but is also the most remote (100 miles northeast of Pitcairn, 400 miles east of Mangareva) and the most marginal for
human existence. Unlike Mangareva or Pitcairn, Henderson is not volcanic
but is in effect a coral reef that geological processes thrust up 100 feet above
sea level. Hence Henderson is devoid of basalt or other rocks suitable for
tool-making. That's a severe limitation for a society of stone tool makers. An additional severe limitation for any humans is that Henderson has no
streams or reliable freshwater sources, because the island consists of porous
limestone. At best, for a few days after the unpredictable arrivals of rain, wa
ter drips from the roofs of caves, and puddles of water can be found on the
ground. There is also a freshwater spring that bubbles up in the ocean about 20 feet offshore. During Marshall Weisler's months on Henderson, he found
obtaining drinking water even with modern tarpaulins to catch the rain a
constant effort, and most of his cooking and all of his washing and bathing
had to be carried out with saltwater.

Even soil on Henderson is confined to small pockets between the lime
stone. The island's tallest trees are only about 50 feet high and not big
enough to fashion into canoe hulls. The resulting stunted forest and thick undergrowth are so dense that they require a machete to penetrate them.
Henderson's beaches are narrow and confined to the north end; its south
coast consists of vertical cliffs where it is impossible to land a boat; and the
south end of the island is a makatea landscape thrown into alternating rows
of razor-sharp limestone ridges and fissures. That south end has been
reached only three times by groups of Europeans, one of them Weisler's group. It took Weisler, wearing hiking boots, five hours to cover the five miles from Henderson's north coast to its south coast
—where he promptly
discovered a rock shelter formerly occupied by barefoot Polynesians.

Offsetting these fearsome disadvantages, Henderson does have attrac
tions. In the reef and shallow waters nearby live lobsters, crabs, octopus, and
a limited variety of fish and shellfish
—unfortunately, not including black-
lipped pearl oyster. On Henderson is Southeast Polynesia's sole known tur
tle nesting beach, where green turtles come ashore to lay eggs between
January and March of each year. Henderson formerly supported at least 17
species of breeding seabirds, including petrel colonies possibly as large as

millions of birds, whose adults and chicks would have been easy to catch on
the nest
—enough for a population of a hundred people each to eat one bird
every day of the year without endangering the colonies' survival. The island
was also home to nine species of resident land birds, five of them flightless or weak fliers and hence easy to catch, including three species of large pi
geons that would have been especially delectable.

All those features would have made Henderson a great place for an after
noon picnic ashore, or for a short vacation to glut yourself on seafood and birds and turtles
—but a risky and marginal home in which to try to eke out
a permanent existence. Weisler's excavations nevertheless showed, to the
surprise of anyone who has seen or heard of Henderson, that the island did evidently support a permanent tiny population, possibly comprising a few
dozen people who went to extreme effort in order to survive. Proof of their
former presence is provided by 98 human bones and teeth representing at
least 10 adults (both men and women, some of them over 40 years old), six
teenaged boys and girls, and four children in the age range of 5 to 10 years.
The children's bones in particular suggest a resident population; modern Pitcairn Islanders usually don't take young children when they visit Hen
derson to collect wood or seafood.

Further evidence of human use is a huge buried midden, one of the
largest known from Southeast Polynesia, running for 300 yards in length
and 30 yards in width along the north-coast beach facing the only passage
through Henderson's fringing reef. Among the midden's garbage left behind
from generations of people feasting, and identified in small test pits exca
vated by Weisler and his colleagues, are enormous quantities of fish bones (14,751 fish bones in just two-thirds of a cubic yard of sand tested!), plus 42,213 bird bones comprising tens of thousands of bones of seabirds (espe
cially petrels, terns, and tropicbirds) and thousands of bones of land birds
(especially the flightless pigeons, rail, and sandpiper). When one extrapo
lates from the number of bones in Weisler's small test pits to the likely num
ber in the whole midden, one calculates that Henderson Islanders must
have disposed of the remains of tens of millions of fish and birds over the centuries. The oldest human-associated radiocarbon date on Henderson is from that midden, and the next-oldest date is from the turtle nesting beach
on the northeast coast, implying that people settled first in those areas where they could glut themselves on wild-caught food.

Where could people live on an island that is nothing more than an up
lifted coral reef covered with low trees? Henderson is unique among islands
inhabited or formerly inhabited by Polynesians in its almost-complete lack

of evidence for buildings, such as the usual houses and temples. There are
only three signs of any construction: a stone pavement and post holes in the
midden, suggesting the foundations of a house or shelter; one small low
wall for protection against the wind; and a few slabs of beach rock for a bur
ial vault. Instead, literally every cave and rock shelter near the coast and with a flat floor and accessible opening
—even small recesses only three
yards wide and two yards deep, barely large enough for a few people to seek
protection from the sun—contained debris testifying to former human
habitation. Weisler found 18 such shelters, of which 15 were on the heavily
used north, northeast, and northwest coasts near the only beaches, and the
other three (all of them very cramped) were on the eastern or southern
cliffs. Because Henderson is small enough that Weisler was able to survey
essentially the entire coast, the 18 caves and rock shelters, plus one shelter on the north beach, probably constitute all the "dwellings" of Henderson's
population.

Charcoal, piles of stones, and relict stands of crop plants showed that the
northeast part of the island had been burned and laboriously converted to
garden patches where crops could be planted in natural pockets of soil, ex
tended by piling surface stones into mounds. Among the Polynesian crops
and useful plants that were introduced intentionally by the settlers, and that
have been identified in Henderson archaeological sites or that still grow
wild on Henderson today, are coconuts, bananas, swamp taro, possibly taro
itself, several species of timber trees, candlenut trees whose nut husks are burned for illumination, hibiscus trees yielding fiber for making rope, and
the ti shrub. The latter's sugary roots serve usually just as an emergency
food supply elsewhere in Polynesia but were evidently a staple vegetable
food on Henderson. Ti leaves could be used to make clothing, house thatch
ing, and food wrappings. All of those sugary and starchy crops add up to a
high-carbohydrate diet, which may explain why the teeth and jaws of Hen
derson Islanders that Weisler found exhibit enough signs of periodontal
disease, tooth wear, and tooth loss to give nightmares to a dentist. Most of
the islanders' protein would have come from the wild birds and seafood, but
finds of a couple of pig bones show that they kept or brought pigs at least
occasionally.

Thus, Southeast Polynesia presented colonists with only a few potentially
labitable islands. Mangareva, the one capable of supporting the largest
copulation, was largely self-sufficient in the necessities for Polynesian life,

except for lacking high-quality stone. Of the other two islands, Pitcairn was
so small, Henderson so ecologically marginal, that each could support only
a tiny population unable to constitute a viable human society in the long
run. Both were also deficient in important resources
—Henderson so much
so that we moderns, who wouldn't dream of going there even for a weekend
without a full tool chest, drinking water, and food other than seafood, find it mind-boggling that Polynesians managed to survive there as residents.
But both Pitcairn and Henderson offered compensating attractions to Poly
nesians: high-quality stone on the former, abundant seafood and birds on
the latter.

Weisler's archaeological excavations uncovered extensive evidence of
trade among all three islands, whereby each island's deficiencies were filled
by the other islands' surpluses. Trade objects, even those (such as ones of
stone) lacking organic carbon suitable for radiocarbon dating, can still be
dated by radiocarbon measurements on charcoal excavated from the same
archaeological layer. In that way, Weisler established that trade began at least
by the year
a.d.
1000, probably simultaneously with the first settlement by humans, and continued for many centuries. Numerous objects excavated at
Weisler's sites on Henderson could immediately be identified as imports be
cause they were made from materials foreign to Henderson: oyster shell
fishhooks and vegetable peelers, volcanic glass cutting tools, and basalt
adzes and oven stones.

Where did those imports come from? A reasonable guess is that the oys
ter shell for fishhooks came from Mangareva, because oysters are abundant there but absent on Pitcairn as well as on Henderson, and other islands with oyster beds are much more distant than Mangareva. A few oyster shell arti
facts have also been found on Pitcairn and are similarly presumed to have come from Mangareva. But it is a much more difficult problem to identify
origins of the volcanic stone artifacts found on Henderson, because both
Mangareva and Pitcairn, as well as many other distant Polynesian islands,
have volcanic sources.

Hence Weisler developed or adapted techniques for discriminating
among volcanic stones from different sources. Volcanoes spew out many
different types of lava, of which basalt (the category of volcanic stone occurring on Mangareva and Pitcairn) is defined by its chemical composition
and color. However, basalts from different islands, and often even from dif
ferent quarries on the same island, differ from each other in finer details of
chemical composition, such as their relative content of major elements (like
silicon and aluminum) and minor elements (like niobium and zirconium).

An even finer discriminating detail is that the element lead occurs naturally
as several isotopes (i.e., several forms differing slightly in atomic weight),
whose proportions also differ from one basalt source to another. To a geolo
gist, all these details of composition constitute a fingerprint that may allow
one to identify a stone tool as coming from one particular island or quarry.

Weisler analyzed the chemical composition and, with a colleague, the
lead isotope ratios in dozens of stone tools and stone fragments (possibly broken off in the course of preparing or repairing stone tools) that he had
excavated from dated layers of archaeological sites on Henderson. For com
parison, he analyzed volcanic rocks from quarries and rock outcroppings on Mangareva and Pitcairn, the most likely sources of rock imported to
Henderson. Just to be sure, he also analyzed volcanic rocks from Polynesian
islands that were much more distant and hence less likely to have served as sources of Henderson imports, including Hawaii, Easter, Marquesas, Soci
eties, and Samoa.

The conclusions emerging from these analyses were unequivocal. All an
alyzed pieces of volcanic glass found on Henderson originated at the Down Rope quarry on Pitcairn. That conclusion had already been suggested by vi
sual inspection of the pieces, even before chemical analysis, because Pitcairn
volcanic glass is colored so distinctively with black and gray patches. Most
of Henderson's basalt adzes, and its basalt flakes likely to have resulted from
adze-making, also originated from Pitcairn, but some came from Man
gareva. On Mangareva itself, although far fewer searches have been made
for stone artifacts than on Henderson, some adzes were also evidently made
from Pitcairn basalt, imported presumably because of its superiority to
Mangareva's own basalt. Conversely, of the vesicular basalt stones excavated
on Henderson, most came from Mangareva, but a minority were from Pit
cairn. Such stones were regularly used throughout Polynesia as oven stones,
to be heated in a fire for cooking, much like the charcoal bricks used in
modern barbecues. Many of those putative oven stones were found in cook
ing pits on Henderson and showed signs of having been heated, confirming
their surmised function.

In short, archaeological studies have now documented a former flour
ishing trade in raw materials and possibly also in finished tools: in oyster shell, from Mangareva to Pitcairn and Henderson; in volcanic glass, from Pitcairn to Henderson; and in basalt, from Pitcairn to Mangareva and Hen
derson, and from Mangareva to Henderson. In addition, Polynesia's pigs
and its bananas, taro, and other main crops are species that did not occur
on Polynesian islands before humans arrived. If Mangareva was settled be-