After a long journey, a group of settlers set foot on otherwise empty land. A vast expanse separates them from other human beings, cutting off all possibility of external contact. Their choices will make the difference between survival and death.
The people of Easter Island may have something to teach future Martian settlers.
Binghamton University anthropologists Carl Lipo and Robert DiNapoli explore how the complex community models of Rapa Nui – the indigenous name of the island and its inhabitants – have helped the isolated island survive since its 12th century settlement. in the 13th century until European contact.
Their results, “Population structure leads to cultural diversity in finite populations: a hypothesis for models of communities located in Rapa Nui (Easter Island, Chile)”, were recently published in the scientific journal PLOS ONE. Co-authors also include Mark Madsen of the Department of Anthropology at the University of Washington and Terry Hunt of Honors College and the School of Anthropology at the University of Arizona.
“What’s cool about Easter Island is that it’s a great case study of what happens in absolute isolation,” said Lipo, professor of anthropology and environmental studies. and associate dean of Harpur College. “To our best understanding, once people got to the island, that was it. They weren’t going anywhere else and there was no one else coming in.”
Shaped like a triangle, Easter Island is small: around 15 miles long and just over 7 miles wide at its thickest point. It is also one of the most remote inhabited places on the planet, over a thousand kilometers from the nearest inhabited neighbors.
But despite its small size, Rapa Nui had several clans and small communities that maintained both cultural and physical separation. Archaeological evidence shows stylistic differences in the creation of artifacts in communities only 500 meters away, for example. The physical remains of the inhabitants also show that they did not move away or marry far from their homes; this was discovered through DNA and isotope analyzes, as well as skeletal variations between communities.
These small communities may have been a cultural bulwark against a phenomenon known as random drift, according to their research.
The challenges of isolation
An idea that has its origins in genetics, Random Drift explores the appearance of traits in a population over time and how those traits can change. This also applies to cultural traits, words and customs specific to the ways of making pottery.
Some traits are passed on to future generations; others are not and subsequently disappear. New traits, practices or fashions emerge – pottery decorating, ways of making arrowheads, dress styles or slang – and also persist or fade over time.
“These things are potentially changing over time because of the differences in the way people copy themselves,” said DiNapoli, postdoctoral researcher in anthropology.
While cosmetic changes may not have a significant impact on the viability of a culture, other changes could. If a population is small and isolated enough, important technologies and survival strategies could be irrevocably lost.
“Let’s say my dad died before he could teach me any important technology and he’s the only person who knows how to do it,” DiNapoli said. “This can have a negative impact on a small, isolated population, where they will never interact with another group of people who might give them these ideas back.”
Researchers believe this is what happened in Tasmania, where indigenous peoples lost practices such as fishing practiced by neighboring populations on the Australian mainland. While these lost technologies might have been beneficial for survival, they disappeared because there were not enough people to pass them on and no contact with outsiders who could have reintroduced these ideas, experts believe.
There is evidence that isolation may have led to the disappearance of populations on the so-called “mystery islands” in the Pacific Ocean. Archaeological records show that previous inhabitants abandoned these islands or went extinct around the time when interaction with other islands disappeared.
“One guess is that as these places get really isolated, then it becomes too difficult to live there, for whatever reason,” Lipo explained.
In recent years, researchers have built different types of models to show which factors lead to changes in the diversity of cultural traits over time, DiNapoli explained. A major factor is demographics: the number of people in the population exchanging ideas. But the structure of this population is also important.
While it may seem counterintuitive, large populations where everyone interacts with each other may experience stronger cultural drift, DiNapoli said.
“Whereas if you have a lot of different small subpopulations, you end up keeping more diversity because it’s sequestered in these different subgroups,” he said.
Traditional populations tend to be extremely conservative and avoid change unless there is a good reason for it. After all, making bad decisions can have dire consequences.
“You really want to hang on to something that works,” Lipo said. “If you decide to take a risk, randomly plant crops elsewhere and it hasn’t worked, the game is over.”
Easter Island is often seen as a place where people made irrational decisions that led to their own demise, like cutting down all the trees to build giant statues. This is not the case – and not just on the front of the statue.
In contact with Europeans, Rapa Nui had an estimated total population of 3,000 to 4,000 individuals, divided into an unknown number of clans and communities. Most of these communities were probably the size of large families – perhaps several dozen individuals, living in a space that stretches several hundred meters.
Using computer modeling, Lipo and DiNapoli explored the impact of the island’s distinctive spatial patterns on the retention of cultural information. In their model, they located communities around ahu, or large platforms that were a center of ceremonial activity. They then configured the ways in which these communities could potentially interact, and what those interactions would have on the persistence of various cultural traits.
What they found is that the greater the number of subgroups with limited interaction, the more likely a population is to retain potentially beneficial cultural information – even when the total population is quite small.
“Based on the simulation modeling, it appears that the population structure is extremely important in driving and sustaining changes in cultural diversity,” DiNapoli said. “It could potentially be a really important driver of change in human history in general.”
Today and tomorrow
After contact with the Europeans, the disease passed through the Rapa Nui, who were also stolen as slaves. In 1877, the island’s population fell to just 111 individuals.
As a result, much of the Rapa Nui’s cultural knowledge was lost, including the ability to interpret rongorongo, a glyph system that may have recorded information. But other traditions survive, including songs, dances, the art of a cat’s cradle-type string used in oral storytelling – and the Rapa Nui language itself, which is still spoken by islanders. today.
“Granted, a lot was lost, but they had these mechanisms to value oral traditions and be able to pass them on,” Lipo said. “It’s incredible survival despite incredible odds. So much has been written on the negative side, and I think we haven’t started to appreciate the ingenuity of the people there yet.”
Imagine another group of intrepid explorers, heading to a new colony aboard their ships, 60 million kilometers from Earth. On Mars, these future settlers would be deeply isolated. They should solve their own problems and ensure their own survival, including the preservation of the necessary knowledge and technology.
“They become this isolated Easter Island in the middle of space,” Lipo said. “What spatial structure on Mars would you need to keep the most information in this community?”
Lessons from Easter Island can help them survive.