Did humans devastate Easter Island on arrival?

19:00 09 March 2006
NewScientist.com news service
Bob Holmes

The first humans may have arrived on Easter Island several centuries later than previously supposed, suggests a new study. If so, these Polynesian settlers must have begun destroying the island's forests almost immediately after their arrival.

Easter Island has often been cited as the classic example of a human-induced ecological catastrophe. The island – one of the most remote places on Earth – was once richly forested, but settlers cut the forests, partly to use the wood in construction of the massive stone statues and temples for which the island is famous. When Dutch sailors arrived in 1722, they found a starving population on a barren island.

Archaeologists had thought that humans first arrived at the island around 800 AD, based on radiocarbon dating of kitchen scraps and cooking fires. Since the first signs of severe deforestation do not appear until the 13th century, this suggests the Easter Islanders lived several centuries without serious impact on their environment.

Not so, says Terry Hunt, an archaeologist at the University of Hawaii at Manoa. Hunt and Carl Lipo of California State University at Long Beach, US, radiocarbon-dated charcoal from the earliest human traces in a new excavation on the island. The site, Anakena, is Easter Island's only sandy beach and has long been regarded as the likeliest spot for first colonists to settle. To their surprise, the wood dated no earlier than 1200 AD – several hundred years more recent than they had expected.
Chop chop

"I got those results back and I was sceptical," says Hunt. "I thought, something's wrong with these." When repeated samples yielded the same date, he and Lipo re-examined the existing evidence. After throwing out any studies that lacked replicate samples or had other methodological problems, the 11 studies that remained all pointed to the same date – roughly 1200 AD.

Such a late arrival date means that the new inhabitants of Easter Island must have begun hacking down trees almost immediately, building the gigantic monuments and stone heads that make the island so distinctive, says Hunt.

And the new civilisation's ecological footprint must have been heavy from the start. "There isn't a period of ecological stability. There was almost immediate impact," says Hunt. "It isn't a two-part story any more. There's really just one chapter."
Broader context

Not everyone is convinced, however. A first arrival on Easter Island around 900 AD would fit well with Polynesians' first arrival on the nearest neighbouring islands of Mangareva, Henderson and Pitcairn, says Patrick Kirch, an archaeologist at the University of California at Berkeley, US.

Kirch thinks Hunt and Lipo may have been too free in discarding studies for minor methodological problems, thus rejecting valid dates in this range. "For me, they don't make a convincing argument that we can eliminate the earlier dates, especially in light of the broader regional context," he says.

And their new excavation may have simply sampled a relatively young settlement while missing nearby, older sites. To resolve the issue, researchers will need to date charcoal from many more excavations to see what pattern emerges. "Then we may be able to say we have the answer," says Kirch.

Journal reference: Science (DOI: 10.1126/science.1121879)

http://www.newscientist.com/channel/being-human/dn8825.html

I still think we dont REALLY know whats up with this island-Az