- Email: [email protected]
Good news you may want to forget
Good news you Chicken-loving Polynesians made it to South America may want to forget
PUNCHSTOCK
www.newscientist.com
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
the University of Auckland in New Zealand and her colleagues carbon dated the bones. “When we got the date I was gobsmacked,” says MatisooSmith. 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
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. D. BEREHULAK/GETTY
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.”
Waves go faster as world warms 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 preindustrial 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.
The frozen north dried African skies 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.
9 June 2007 | NewScientist | 23
PUNCHSTOCK
www.newscientist.com
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
the University of Auckland in New Zealand and her colleagues carbon dated the bones. “When we got the date I was gobsmacked,” says MatisooSmith. 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
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. D. BEREHULAK/GETTY
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.”
Waves go faster as world warms 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 preindustrial 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.
The frozen north dried African skies 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.
9 June 2007 | NewScientist | 23