Easter Island, known as Rapa Nui in the native language, is a tiny speck of land smack in the middle of the South Pacific. For millions of years, the island was only inhabited by sea birds and dragonflies until a weary group of Polynesian seafarers — perhaps a single-family — disembarked from their double-hulled canoe on the island at around the year 1200 C.E.
From there on until contact with European settlers centuries later, the people of Easter Island lived in absolute isolation from the outside world. No one from Easter Island sailed back to the mainland, which is thousands of miles away, nor did anyone from the mainland come to visit.
Easter Island is famous for its 70-ton carved statues that dot its surface. But among academics, the story of Easter Island is often used to illustrate what happens when a society destroys itself by overexploiting its own resources. When the first people arrived on the 63-square-mile patch of land, the place was covered with as many as 15 million trees.
But the settlers, who were slash-and-burn farmers, burned down most of the woods to open up space for crops and gather building material. Within a couple of generations, the island reached an unsustainable number of people, about 3,000 to 4,000 people at its height, and too few trees. Some other generations later, there were barely any trees left at all. What was once a thriving community became a shadow of its former self, with the island’s inhabitants condemned to living marginal lives, their once mighty canoes reduced to fragments of driftwood.
In his best-selling book, Collapse, author Jared Diamond called Easter Island’s self-destructive behavior “ecocide”, and warned that the island’s fate could one day be our own on a planetary level.
However, there are also positive lessons that can be learned from such a uniquely isolated community. In a new study published today in the journal PLOS ONE, an international team of researchers explored how complex community patterns helped the islands survive for centuries.
“The cool thing about Easter Island is that it’s a great case study for what happens in absolute isolation,” said Carl Lipo, a professor of anthropology and environmental studies at Binghamton University. “From our best understanding, once people got to the island, that was it. They weren’t going anywhere else and there wasn’t anyone else coming in.”
Despite the island’s small size, measuring just 15 miles long and 7 miles wide, the Rapa Nui people were segregated into multiple clans that maintained both cultural and physical separation. Thanks to these independent sub-groups, the islanders preserved cultural diversity despite the small population size.
Strikingly, archaeological evidence shows stylistically distinct artifacts in communities only 500 meters apart. DNA and isotope analyses of the natives’ physical remains also showed that they didn’t stray too far from their homes.
This clan-separation of the inhabitants may have saved these small communities of cultural random drift. This phenomenon was originally proposed in genetics to describe a mechanism of evolution in which allele (gene variants) frequencies of a population change over generations due to chance rather than natural selection. Random drift, or genetic drift, happens in all populations but it is most impactful in small populations, such as an isolated patch of vegetation or a small community of people in the middle of the Pacific.
In time, random drift can uniformize a population’s genotype, the loss of some alleles (including beneficial ones), and the fixation, or rise to %100, percent frequency, of other alleles.
This concept also applies culturally. If a community of people is very small, over time specific cultural traits, such as specific words, customs, or techniques (i.e. making pottery, tool manufacturing, etc) can vanish because there’s no one left to pass down the information to subsequent generations.
“These things are potentially changing over time because of differences in how people are copying each other,” Robert DiNapoli, co-author of the study and an anthropologist at Binghamton University.
“Let’s say my dad died before he was able to teach me some important technology and he’s the only person who knew how to do it,” DiNapoli said. “That can have a negative impact in a small, isolated population, where they never will interact with another group of people who might give them those ideas back again.”
The researchers give several examples where isolation eventually wiped out populations. Indigenous people in Tasmania lost certain skills such as fishing techniques practiced by people on neighboring mainland Australia. Isolation is also blamed for the disappearance of populations on the “mystery islands” of the Pacific Ocean.
But the new study shows that while the number of people of a population is highly important when it comes to driving changes in the diversity of cultural traits over time, so is the structure of the population.
“Whereas if you have lots of different small subpopulations, you end up keeping more diversity, because it’s sequestered in these different subgroups,” DiNapoli said.
With the help of a computer model, the researchers simulated how the island’s distinctive clans affected the retention of cultural information and how they interacted with one another.
The results suggest that the greater the number of subgroups with limited interaction, the more likely it is that a population will retain potentially beneficial cultural information, a shield against random drift.
“Based on simulation modeling, it seems that population structure is super important for driving and retaining changes in cultural diversity,” DiNapoli said. “This could potentially be a really important factor for change in human history in general.”
Much of the cultural heritage of the Rapa Nui has been lost forever or was eradicated when Europeans arrived in greater numbers, following Captain James Cook’s first visit there in 1774. By 1877, only 111 natives were left alive after diseases brought by the new settlers destroyed the population, and these natives were taken away as slaves. Now, no one knows how to interpret rongorongo, a system of glyphs that the islanders may have used to record information.
Yet despite all their hardship and near-total obliteration, there are still some Rapa Nui cultural customs that have miraculously survived. These include songs, dances, and a cat’s cradle-type of string art used in oral storytelling.
Against all odds, the Rapa Nui culture lived on — and there may be highly important valuable lessons to be learned from all of this for future intrepid explorers. The dangerous journey to Easter Island in the early 1200s can be compared to a manned trip to Mars. On the Red Planet, humans that are there for good in order to colonize Mars will remain profoundly isolated, and so will their children’s children.
“They become this isolated Easter Island in the middle of space,” Lipo said. “What spatial structure on Mars would you need to maintain the information maximally in that community?”
