DNA from archaeological sites in

Polynesia, they found an identical

match with samples from Tonga

and American Samoa, and a near

identical match from Easter

Island (Proceedings of the National Academy of Sciences,

DOI: 10.1073/pnas.0703993104).

Because Easter Island is in

eastern Polynesia, it is a more

likely launch point for a voyage to

South America. The journey

would have taken less than two

weeks, which is within the range

for Polynesian voyages around

this time, says Matisoo-Smith.

the University of Auckland in

New Zealand and her colleagues

carbon dated the bones.

“When we got the date I was

gobsmacked,” says Matisoo-

Smith. The 50 chicken bones came

from at least five different birds

and date from between 1321 and

1407. While Columbus didn’t

arrive until 1492, the timescale for

the bones coincides with the

colonisation of the easternmost

islands of Polynesia, including

Pitcairn and Easter Island.

When the team compared the

Chilean chicken DNA with chicken

GIGANTIC ocean waves, spanning

hundreds of kilometres from

crest to crest, have been speeding

up thanks to global warming, a

new model suggests .

Geophysicists predict that as

the ocean surface warms, these

so-called planetary waves should

speed up. To test this idea, John

Fyfe and Oleg Saenko at the

University of Victoria in British

Columbia, Canada, modelled the

changes to ocean wave patterns

over the 20th and 21st centuries.

“We were really surprised at

how quickly the ocean responded

to temperature change,” Fyfe says.

According to the model, global

warming has already increased

the speed of the waves, but no

one noticed because satellites

have not been monitoring their

speeds for long enough, he says.

The model also shows that by the

end of the 21st century, the waves

will be a further 20 to 40 per cent

faster compared with pre-

industrial speeds (Geophysical Research Letters, vol 34, p L10706).

“We knew we’d see an effect,

but we didn’t think it would be

significant for at least another two

centuries,” Fyfe says. The faster

planetary waves will have an

effect on global weather, he adds.

Waves go faster

as world warms

WHEN ice ages held Europe in their

grip, Africa also felt the pinch –

though in a different way.

It has long been suspected that

there is a connection between the

west African monsoon and climate at

higher latitudes – especially over

geological timescales, says David Lea

at the University of California, Santa

Barbara. “But until now, there hasn’t

been enough supporting evidence.”

Now Lea, with team leader Syee

Weldeab and colleagues, has

reconstructed the most detailed

history of the monsoon yet, spanning

155,000 years and two ice ages.

The team analysed the amount of

barium in plankton shells found in an

ocean sediment core drilled beneath

the Gulf of Guinea. Barium is found

in freshwater run-off from the river

Niger, says Lea, and is a gauge of past

run-off levels and monsoon

intensities. When the northern

latitudes were frozen over, monsoon

rains were much weaker, only gaining

strength again when the temperatures

in the north increased, the team found.

They also discovered big swings in

monsoon activity over timescales as

small as 100 years, linked to rapid

climate change caused by changes in

ice sheet size (Science, vol 316, p 1303).

“Something that happens right up in

the poles can have a dramatic effect

on the climate in the tropics,” says Lea.

A NOTE to the forgetful: failing to

remember everything is a sign your

brain is working properly. So says a

study that found that the brain not

only chooses to reinforce memories it

deems most relevant, but actively

suppresses those that

are similar but less-used.

Brice Kuhl at Stanford University

in California and his colleagues used

functional magnetic resonance

imaging (fMRI) to measure the brain

activity of 20 healthy adults while

they performed a simple memory

test. Participants were given three

word pairs to memorise, two of

which were closely associated with

each other. After studying one of the

associated pairs for a second time,

subjects were asked to recall all three

pairs. On average, people were 15 per

cent worse at recalling the associated

pair they had seen once than they

were at recalling the unrelated pair.

The fMRI scans showed that

during the test, participants’ brains

were highly active in a region known

to handle competing memories and

another believed to induce memory

suppression. As the test was

repeated, the level of suppression

lessened, indicating the memory

adjustment had been made (Nature Neuroscience, DOI: 10.1038/nn1918).

“The process of forgetting serves

a good functional purpose,” says

Michael Anderson of the University of

Oregon in Eugene. “These guys have

clearly established the neurobiological

basis for this process.”

CHICKEN was on the menu in

the Americas at least 100 years

before Europeans arrived.

The birds were introduced by

Polynesians, according to an

analysis of chicken bones found

on the Arauco Peninsula in

south-central Chile.

It’s the first concrete evidence

that Polynesians voyaged as far as

South America, and also suggests

that they, not Europeans, were

responsible for introducing

chickens to the continent. Both

topics have been hotly debated.

Elizabeth Matisoo-Smith from

PUNC

HSTO

CK

D. B

EREH

ULAK

/GET

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Chicken-loving Polynesians made it to South AmericaGood news you may want to forget

The frozen north dried African skies

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