Evrim Yazgin
Cosmos science journalist
Ancient rock walls, high mounds and ditches discovered in Sāmoa point to the origins of social hierarchy in Polynesian society.
A study published in the journal PLOS One links dramatic population growth and rich agricultural land in some areas with the beginnings of land and social status division in Sāmoa.
Fieldwork at the site in the dense jungle of the Falefa Valley on ‘Upolu island was based on plane-mounted LiDAR (Light Detection and Ranging). This mapping technology uses laser pulses to measure distances through thick foliage to create a topographic map.
“This technology has been used for the past 15 to 20 years around the Pacific, and the great thing it can do is strip away even a dense jungle environment,” says lead researcher Ethan Cochrane from the University of Auckland in New Zealand.
“This is one of the first times it’s been used in Sāmoa, so all these impressive rock walls, platforms and mounds, which date back between 600 and 900 years, can be seen in precise detail.”
Using the LiDAR-created map as a guide, the archaeologists were able to find the site.
“These structures up close are incredible pieces of architecture. Some were family dwellings made from stone and earth, just like you see today in some Sāmoan villages, others would have been civic construction projects or ceremonial projects. Some are what are called ‘star mounds’, as high as 2 metres,” Cochrane adds.
It’s not the first time such structures have been found in Sāmoa, but it’s the first time their construction has been associated with the ‘collective action problem.’
This is when individuals in a society would be better off cooperating, but cannot due to competing interests.
“We’ve figured out that this building of stuff – kilometre-long rock walls that limit access to land, ditches for irrigation to create a productive wetland agricultural system – is a response to a massive population rise in Sāmoa that we know happened around that time,” Cochrane explains.
“In this instance, sharing resources with everyone would mean less for everyone, so the problem becomes, ‘when does it become advantageous for individuals to contribute to collective defence at a cost to themselves and to exclude other groups from access to the group’s resources?’”
Soil samples confirm that the walls protected access to more fertile land and valuable resources. The team suggest that increases in population may have been the catalyst for the development of the Sāmoan chiefly system which is present across Polynesian society.
Cochrane suggests that similar pressures might have seen the emergence of hierarchy in early societies worldwide.
“We’ve often wondered why hierarchical societies arose across the planet over millennia, when around 20,000 years ago, most human societies were more equitable and there were fewer positions of status and power among hunter gatherers,” Cochrane adds.
