- Email: [email protected]
A little aspirin may prevent bowel cancer
IN BRIEF
jimmy westlake colorado mountain college
AN ASTEROID that is the source of an annual meteor shower may owe its weird crumbliness to intense cooking by the sun. Most meteor showers are thought to come from comets, whose icy surfaces vaporise easily during close encounters with the sun. Dust that is liberated in the process burns up in Earth’s atmosphere, creating “shooting stars”. However, the debris stream responsible for the annual Geminid shower in December follows the orbit of a 5-kilometre-wide object called 3200 Phaethon, which appears to be an asteroid. So how does the rocky body cast off so much material without any ice to vaporise? A clue came in June 2009, when NASA’s STEREO-A spacecraft watched the asteroid double in brightness at its closest point to the sun, which lies just 14 per cent of Earth’s distance from the star. Now David Jewitt and Jing Li, both at the University of California, Los Angeles, say the asteroid’s sunward face should have reached a searing 480 to 780 °C at that point. That is hot enough to make its rocks expand and crack, generating dust that reflected sunlight and caused the asteroid to brighten (The Astronomical Journal, in press).
20 | NewScientist | 25 September 2010
City-dwelling helped us evolve resistance to disease LIVING in a crowded city doesn’t sound like a recipe for good health, but it may have helped our ancestors protect their descendants from disease. Some people carry a genetic sequence, or allele, that provides immunity to leprosy and tuberculosis. Mark Thomas at University College London wondered whether this genetic immunity could have been gained when people began living in close proximity. Poor sanitation would have meant that disease was rife in ancient cities, but exposure to
the pathogens would have led to resistance developing, which the inhabitants would have passed on to their descendants. To test this idea, Thomas and colleagues analysed the DNA of people living in 12 regions in Europe, Asia and Africa. For each area, they combed the historical and anthropological records to work out when people first started living in close-knit groups. They found that the longer cities in the region had been established, the more likely it was that the current inhabitants carried the
immunity allele (Evolution, DOI: 10.1111/j.1558-5646.2010.01132.x). It had been thought that the allele became prevalent when cattle were first domesticated, as cows carry a strain of TB that humans can catch. But the team found a stronger correlation between the allele and urbanisation than with the onset of cattle farming. Thomas describes population dynamics as “an underplayed feature of our history” and thinks resistance to other diseases could also have evolved in this way. pete turner/getty
Strange source of shooting stars
For new stories every day, visit www.NewScientist.com/news
A mini aspirin a day keeps cancer away A LITTLE aspirin might just go as far as a lot when it comes to preventing bowel cancer – with fewer side effects. So says a five-year retrospective study led by Malcolm Dunlop of the University of Edinburgh, UK, that compared the aspirin habits of 2800 people with cancer and 3000 without. The team found that the risk of getting cancer was 25 per cent lower in those who had been taking 75 milligrams of the drug daily compared with those who had not (Gut, DOI: 10.1136/ gut.2009. 2030 00). If everyone in the UK was taking a low dose of aspirin in 2007, the latest year for which data on bowel cancer incidence data is available, it would have prevented 16 cases per 100,000. This small reduction in risk is comparable to that from earlier studies in which the doses were much higher. Andrew Chan of Harvard Medical School in Boston is not convinced: “I still believe that lower doses are not as effective as higher ones.” His 20-year follow-ups on 80,000 women and 50,000 men showed that daily doses of 325 milligrams worked best for preventing bowel cancer.
Fewer trees below, less ice up top AGGRESSIVE tree-felling on mount Kilimanjaro could be partly to blame for its vanishing ice cap. The ice on Kilimanjaro’s summit has shrunk to just 15 per cent of its extent in 1912, leading campaigners to hold it up as a symbol of climate change. But other factors are also at play. For instance, the air at the summit is getting drier, reducing the snowfall that replenishes the ice and reflects solar radiation. Now Nicholas Pepin from the University of Portsmouth, UK, and colleagues say deforestation could be an important part of the puzzle.
Between September 2004 and July 2008, the team took hourly humidity and temperature readings at 10 elevations on the mountain. These revealed that daytime heating generates a flow of warm, moist air up the mountainside (Global and Planetary Change, DOI: 10.1016/ j.gloplacha.2010.08.001). Trees play an important role here by providing moisture through transpiration. Pepin suggests that extensive local deforestation in recent decades has likely reduced this flow of moisture, depleting the mountain’s icy hood.
jimmy westlake colorado mountain college
AN ASTEROID that is the source of an annual meteor shower may owe its weird crumbliness to intense cooking by the sun. Most meteor showers are thought to come from comets, whose icy surfaces vaporise easily during close encounters with the sun. Dust that is liberated in the process burns up in Earth’s atmosphere, creating “shooting stars”. However, the debris stream responsible for the annual Geminid shower in December follows the orbit of a 5-kilometre-wide object called 3200 Phaethon, which appears to be an asteroid. So how does the rocky body cast off so much material without any ice to vaporise? A clue came in June 2009, when NASA’s STEREO-A spacecraft watched the asteroid double in brightness at its closest point to the sun, which lies just 14 per cent of Earth’s distance from the star. Now David Jewitt and Jing Li, both at the University of California, Los Angeles, say the asteroid’s sunward face should have reached a searing 480 to 780 °C at that point. That is hot enough to make its rocks expand and crack, generating dust that reflected sunlight and caused the asteroid to brighten (The Astronomical Journal, in press).
20 | NewScientist | 25 September 2010
City-dwelling helped us evolve resistance to disease LIVING in a crowded city doesn’t sound like a recipe for good health, but it may have helped our ancestors protect their descendants from disease. Some people carry a genetic sequence, or allele, that provides immunity to leprosy and tuberculosis. Mark Thomas at University College London wondered whether this genetic immunity could have been gained when people began living in close proximity. Poor sanitation would have meant that disease was rife in ancient cities, but exposure to
the pathogens would have led to resistance developing, which the inhabitants would have passed on to their descendants. To test this idea, Thomas and colleagues analysed the DNA of people living in 12 regions in Europe, Asia and Africa. For each area, they combed the historical and anthropological records to work out when people first started living in close-knit groups. They found that the longer cities in the region had been established, the more likely it was that the current inhabitants carried the
immunity allele (Evolution, DOI: 10.1111/j.1558-5646.2010.01132.x). It had been thought that the allele became prevalent when cattle were first domesticated, as cows carry a strain of TB that humans can catch. But the team found a stronger correlation between the allele and urbanisation than with the onset of cattle farming. Thomas describes population dynamics as “an underplayed feature of our history” and thinks resistance to other diseases could also have evolved in this way. pete turner/getty
Strange source of shooting stars
For new stories every day, visit www.NewScientist.com/news
A mini aspirin a day keeps cancer away A LITTLE aspirin might just go as far as a lot when it comes to preventing bowel cancer – with fewer side effects. So says a five-year retrospective study led by Malcolm Dunlop of the University of Edinburgh, UK, that compared the aspirin habits of 2800 people with cancer and 3000 without. The team found that the risk of getting cancer was 25 per cent lower in those who had been taking 75 milligrams of the drug daily compared with those who had not (Gut, DOI: 10.1136/ gut.2009. 2030 00). If everyone in the UK was taking a low dose of aspirin in 2007, the latest year for which data on bowel cancer incidence data is available, it would have prevented 16 cases per 100,000. This small reduction in risk is comparable to that from earlier studies in which the doses were much higher. Andrew Chan of Harvard Medical School in Boston is not convinced: “I still believe that lower doses are not as effective as higher ones.” His 20-year follow-ups on 80,000 women and 50,000 men showed that daily doses of 325 milligrams worked best for preventing bowel cancer.
Fewer trees below, less ice up top AGGRESSIVE tree-felling on mount Kilimanjaro could be partly to blame for its vanishing ice cap. The ice on Kilimanjaro’s summit has shrunk to just 15 per cent of its extent in 1912, leading campaigners to hold it up as a symbol of climate change. But other factors are also at play. For instance, the air at the summit is getting drier, reducing the snowfall that replenishes the ice and reflects solar radiation. Now Nicholas Pepin from the University of Portsmouth, UK, and colleagues say deforestation could be an important part of the puzzle.
Between September 2004 and July 2008, the team took hourly humidity and temperature readings at 10 elevations on the mountain. These revealed that daytime heating generates a flow of warm, moist air up the mountainside (Global and Planetary Change, DOI: 10.1016/ j.gloplacha.2010.08.001). Trees play an important role here by providing moisture through transpiration. Pepin suggests that extensive local deforestation in recent decades has likely reduced this flow of moisture, depleting the mountain’s icy hood.