What happened to the people of Easter Island is one of history's most enduring mysteries. We know the island's population was devastated but we don't know why – though recent research suggests there was more to it than just "ecocide" (exhaustion of resources). Yet another mystery is how big the population was to begin with.

When the Dutch arrived on Easter Island in 1722, they estimated a population size of 1,500 to 3,000 people. Even then, they expressed bewilderment at how such a tiny population could create the giant stone statues that the island is famous for. 

But current ethnographic and archeological evidence suggests the population wasn't always as small as it was when the Europeans found it, and just last week a group of academics gave us the best estimate so far. Based on the island's farming potential, they calculated a peak population size of 17,500. The results were published in Frontiers in Ecology and Evolution.

"Despite its almost complete isolation, the inhabitants of Easter Island created a complicated social structure and these amazing works of art before a dramatic change occurred," said lead author Dr Cedric Puleston, from the Department of Anthropology at the University of California, Davis, in a statement.

"We've tried to solve one piece of the puzzle – to figure out the maximum population size before it fell. It appears the island could have supported 17,500 people at its peak, which represents the upper end of the range of previous estimates."

As Puleston pointed out, "If the population fell from 17,500 to the small number that missionaries counted many years after European contact, it presents a very different picture from the maximum population of 3,000 or less that some have suggested."

The team discovered that 19 percent of the island could have been used to grow sweet potatoes, the Islanders' primary food crop. By looking at birth and death rates and how they are affected by food availability, the researchers worked out how many people could have survived on the island.

"The result is a wide range of possible maximum population sizes, but to get the smallest values you have to assume the worst of everything," explained Puleston. 

"If we compare our agriculture estimates with other Polynesian Islands, a population of 17,500 people on this size of island is entirely reasonable."

This discovery takes us one step closer to unraveling the mystery of Easter Island.

"As an extremely unusual case, in both its cultural achievements and its ecological transformation, Easter Island is remarkable and important. It retains an air of mystery, but it's a real place and has a real history lived by real people. Dispelling that mystery brings us closer to understanding the nature of humanity," said Puleston.