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Dying Tasmanian devils turn to teen pregnancies
TASMANIAN DEPARTMENT OF PRIMARY INDUSTRIES/AP/PA
IN WHAT seems like a desperate bid to survive, Tasmanian devils are showing precocious sexual behaviour in populations that have been devastated by the fatal devil facial tumour disease. Menna Jones of the University of Tasmania in Hobart monitored the age at which females produced their first litter in five populations of Tasmanian devils before and after the disease had become established. Female Tasmanian devils usually breed at 2, 3 and 4 years old, with up to four pups per litter, then die at 5 years old. The team found that where the disease is established, life expectancy falls to 2 to 3 years. In some of these groups, up to 80 per cent of females bred at 1 year old compared with less than 10 per cent before the cancer appeared (Proceedings of the National Academy of Sciences, DOI: 10.1073/pnas.0711236105). “We found a sixteenfold increase in precocious breeding. They are fitting in an extra litter when they are teenagers,” says Jones. The trigger for early breeding is unknown, but Jones suggests that it could be increased food supplies as a result of reduced competition from older individuals. Devil facial tumour disease is a communicable cancer spread by biting that was first reported in 1996. By 2007 it had spread across more than half the animal’s range in Tasmania, leading some experts to predict that the disease could make the animal extinct in the wild within 25 years.
www.newscientist.com
Babies boost their working memory just as adults do EVER suffer from memory overload? It’s a common problem because adults can only hold three things in their working memories at a time. We expand this pitiful capacity by grouping things into hierarchical categories – we remember phone numbers in clusters of numerals, for instance. You might think we learn this technique as we mature. Not a bit of it. Babies also remember only three things at a time, and they get past the limitation by categorising. Lisa Feigenson and colleagues
at Johns Hopkins University in Baltimore, Maryland, showed 14month-old babies four toys, then hid them in a box where the baby could retrieve them, hiding one in a secret compartment out of reach. When the researchers showed a baby two cats and two cars, then placed them in the box with one out of reach, the baby retrieved the three toys then kept looking, remembering there was one left. But with toys the babies were less familiar with and couldn’t categorise – shrimps and tanks – they didn’t look for the fourth toy.
However, if the researchers helped the babies group these toys – either by initially presenting the shrimps and tanks, or even identical toy balls, in spatially separate groups, or naming them with different nonsense words – then the babies remembered when there were more than three and kept looking (Proceedings of the National Academy of Sciences, DOI: 10.1073pnas.0709884105) “This shows for the first time that babies use the same mental organisation as adults,” says Feigenson.
Asteroid attraction kept Mars magnetic
of an orbiting asteroid may have powered a dynamo by pulling on the fluid in Mars’s core. The team’s lab and model simulations showed that an asteroid orbiting 75,000 kilometres above Mars could have maintained a dynamo for 400 million years, before the rock crashed into the planet and switched it off (Journal of Geophysical Research, DOI: 10.1029/2007JE002982). Some researchers are sceptical. While an asteroid might have had enough energy to churn fluid in the planet’s core, much more energy is needed to set up the dynamo to begin with, according to David Stevenson of the California Institute of Technology in Pasadena. “It would be like looking at a boulder on top of a hill without asking what it took to get it there,” he says.
NASA/ROYMER RESSMEYER/CORBIS
Dying devils turn to teen pregancies
There’s no ‘p’ in climate change WE MIGHT soon be feeling the effects of climate change inside as well as all around us. Kidney stones are expected to strike around 2.25 million more Americans by 2050, as temperature rises cause more people to become dehydrated. These excruciatingly expelled calcium deposits are caused by low urine volume. About 13 per cent of men and 7 per cent of women in the US develop kidney stones during their lives, but those rates are much higher in an area of the south with high temperatures, nicknamed the kidney-stone belt. Tom Brikowski of the University of Texas, Dallas, and his colleagues used the most up-to-date model of climate change, and population trends to predict how the prevalence of kidney stones may change in the US. California, Texas, Florida and the north-east will see the most new cases, and while the team hasn’t yet modelled data for the rest of the world, people in Asia and Eastern Europe could also be in for a painful future, Brikowski says (Proceedings of the National Academy of Sciences, DOI: 10.1073/pnas.0709652105). Drinking more water is one way of combating the problem.
CAN you flip a planet’s magnetic field on and off like a light switch? An asteroid could have done just that to Mars 4 billion years ago. Mars once had a magnetic field, which may have been driven by a dynamo formed from the convection of material in the core, much like the Earth’s is today. Yet crater records suggest the Martian dynamo died quickly, over a few tens of thousands of years, something researchers struggle to explain. Now Jafar Arkani-Hamed of the University of Toronto, Canada, and colleagues say the gravitational tug
19 July 2008 | NewScientist | 17
IN WHAT seems like a desperate bid to survive, Tasmanian devils are showing precocious sexual behaviour in populations that have been devastated by the fatal devil facial tumour disease. Menna Jones of the University of Tasmania in Hobart monitored the age at which females produced their first litter in five populations of Tasmanian devils before and after the disease had become established. Female Tasmanian devils usually breed at 2, 3 and 4 years old, with up to four pups per litter, then die at 5 years old. The team found that where the disease is established, life expectancy falls to 2 to 3 years. In some of these groups, up to 80 per cent of females bred at 1 year old compared with less than 10 per cent before the cancer appeared (Proceedings of the National Academy of Sciences, DOI: 10.1073/pnas.0711236105). “We found a sixteenfold increase in precocious breeding. They are fitting in an extra litter when they are teenagers,” says Jones. The trigger for early breeding is unknown, but Jones suggests that it could be increased food supplies as a result of reduced competition from older individuals. Devil facial tumour disease is a communicable cancer spread by biting that was first reported in 1996. By 2007 it had spread across more than half the animal’s range in Tasmania, leading some experts to predict that the disease could make the animal extinct in the wild within 25 years.
www.newscientist.com
Babies boost their working memory just as adults do EVER suffer from memory overload? It’s a common problem because adults can only hold three things in their working memories at a time. We expand this pitiful capacity by grouping things into hierarchical categories – we remember phone numbers in clusters of numerals, for instance. You might think we learn this technique as we mature. Not a bit of it. Babies also remember only three things at a time, and they get past the limitation by categorising. Lisa Feigenson and colleagues
at Johns Hopkins University in Baltimore, Maryland, showed 14month-old babies four toys, then hid them in a box where the baby could retrieve them, hiding one in a secret compartment out of reach. When the researchers showed a baby two cats and two cars, then placed them in the box with one out of reach, the baby retrieved the three toys then kept looking, remembering there was one left. But with toys the babies were less familiar with and couldn’t categorise – shrimps and tanks – they didn’t look for the fourth toy.
However, if the researchers helped the babies group these toys – either by initially presenting the shrimps and tanks, or even identical toy balls, in spatially separate groups, or naming them with different nonsense words – then the babies remembered when there were more than three and kept looking (Proceedings of the National Academy of Sciences, DOI: 10.1073pnas.0709884105) “This shows for the first time that babies use the same mental organisation as adults,” says Feigenson.
Asteroid attraction kept Mars magnetic
of an orbiting asteroid may have powered a dynamo by pulling on the fluid in Mars’s core. The team’s lab and model simulations showed that an asteroid orbiting 75,000 kilometres above Mars could have maintained a dynamo for 400 million years, before the rock crashed into the planet and switched it off (Journal of Geophysical Research, DOI: 10.1029/2007JE002982). Some researchers are sceptical. While an asteroid might have had enough energy to churn fluid in the planet’s core, much more energy is needed to set up the dynamo to begin with, according to David Stevenson of the California Institute of Technology in Pasadena. “It would be like looking at a boulder on top of a hill without asking what it took to get it there,” he says.
NASA/ROYMER RESSMEYER/CORBIS
Dying devils turn to teen pregancies
There’s no ‘p’ in climate change WE MIGHT soon be feeling the effects of climate change inside as well as all around us. Kidney stones are expected to strike around 2.25 million more Americans by 2050, as temperature rises cause more people to become dehydrated. These excruciatingly expelled calcium deposits are caused by low urine volume. About 13 per cent of men and 7 per cent of women in the US develop kidney stones during their lives, but those rates are much higher in an area of the south with high temperatures, nicknamed the kidney-stone belt. Tom Brikowski of the University of Texas, Dallas, and his colleagues used the most up-to-date model of climate change, and population trends to predict how the prevalence of kidney stones may change in the US. California, Texas, Florida and the north-east will see the most new cases, and while the team hasn’t yet modelled data for the rest of the world, people in Asia and Eastern Europe could also be in for a painful future, Brikowski says (Proceedings of the National Academy of Sciences, DOI: 10.1073/pnas.0709652105). Drinking more water is one way of combating the problem.
CAN you flip a planet’s magnetic field on and off like a light switch? An asteroid could have done just that to Mars 4 billion years ago. Mars once had a magnetic field, which may have been driven by a dynamo formed from the convection of material in the core, much like the Earth’s is today. Yet crater records suggest the Martian dynamo died quickly, over a few tens of thousands of years, something researchers struggle to explain. Now Jafar Arkani-Hamed of the University of Toronto, Canada, and colleagues say the gravitational tug
19 July 2008 | NewScientist | 17