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Alive! We survived a post Toba winter
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Dougal Waters/Getty
THE fastest thing in the universe has come to a complete stop for a record-breaking minute. At full pelt, light would travel about 18 million kilometres in that time – that’s more than 20 round trips to the moon. Light was first stopped in 2001 for a fraction of a second. Earlier this year, researchers kept it still for a record 16 seconds using cold atoms. To break the minute barrier, George Heinze and colleagues at the University of Darmstadt, Germany, fired a control laser at an opaque crystal, sending its atoms into a quantum superposition of two states. This made it transparent to a narrow range of frequencies. Heinze’s team then halted a second beam that entered the crystal by switching off the first laser and hence the transparency. The storage time depends on the crystal’s superposition. A magnetic field extends it but complicates the control laser configuration. Heinze’s team used an algorithm to “breed” combinations of magnet and laser, leading them to one that trapped light for a minute (Physical Review Letters, doi.org/m86). They used the trap to store and then retrieve an image consisting of three stripes. The feat could enable a quantum repeater, which would stop and then re-emit photons used in secure communications, to preserve their quantum state over long distances.
Would-be fathers, your sperm clock is ticking IT’S not just women who have to worry about their ticking reproductive clock. Men’s sperm quality seems to deteriorate after the age of 35. The proportion of sperm carrying an X chromosome also seems to increase, meaning older dads are more likely to have daughters. It has been controversial whether the quality and quantity of a man’s sperm deteriorates with age. “However, there is fairly convincing epidemiological evidence that older men do find it harder to conceive a child –
regardless of female age – and as men get older their partners are at increased risk of miscarriage,” says Allan Pacey, a fertility specialist at the University of Sheffield, UK. There is also a slightly increased risk of older men fathering children with genetic disorders. To investigate, Bronte Stone at Reproductive Technology Laboratories in Los Angeles and his colleagues analysed sperm samples from 5081 men aged between 16 and 72. They found a deterioration in sperm quality and quantity after age 35. Some
previous studies had suggested that the decline doesn’t start until around five years later (Fertility and Sterility, doi.org/m85). “Whether it’s 35 or 40, the message from this and other papers is that men should be aware of age-related changes in their reproductive system and if they wish to become fathers they shouldn’t leave it too late,” Pacey says. The study also found a decrease in the ratio of Y to X-bearing sperm once men hit 55, though it is not clear why. Paulo Ricardo de Oliveira Roth
Light stopped for a whole minute
Alive! We survived a post Toba winter NO ARK required. Animals survived the flood of lava that erupted from the Toba supervolcano about 74,000 years ago just fine on their own, a new genetic analysis shows. The finding casts doubt on the theory that humans were almost wiped out around that time by a “volcanic winter” – an idea that comes from genetic data showing that the population rapidly expanded just after that time, as if it had recently collapsed. If Toba caused such a collapse, humans would not have been the only ones affected, reasoned Geoffrey Hayes of Northwestern University in Chicago. His team examined the DNA of 19 mammal species from every continent looking for a similar genetic pattern. It showed up in seven of them, but only coincided with Toba in two – the Siberian roe deer and Chinese black snub-nosed monkey. The results are not proof: Toba might still have devastated the human population, Hayes says, but it is another piece of evidence against it. The work was presented at the Society for Molecular Biology and Evolution meeting in Chicago this month.
Tiny heir of the sabre-toothed cats COULD this little guy be the best living representative of the extinct sabre-toothed cats? If so, the South American short-tailed opossum could help us understand how the iconic predators used their teeth. Despite being just 10 centimetres long, the short-tailed opossum is aggressive and will attack larger mammals. Ernesto Blanco at the University of the Republic in Montevideo, Uruguay, and colleagues made skull measurements on four of the opossums, along with 40 other South American marsupial predators. They then compared the results with
corresponding data on the skulls of extinct sabre-toothed animals. The opossums’ canines are much larger relatively than those of the other living animals in the study, and their jaws open unusually wide. Their bite is relatively weak, as modelling suggests was true of sabre-toothed cats. Blanco suggests opossums may be evolving along similar lines. He adds that their large teeth probably evolved to attract mates (Journal of Zoology, doi.org/m89). The clouded leopard has also been touted as a living analogue of the cats, but is little studied as it is so rare.
27 July 2013 | NewScientist | 19
Dougal Waters/Getty
THE fastest thing in the universe has come to a complete stop for a record-breaking minute. At full pelt, light would travel about 18 million kilometres in that time – that’s more than 20 round trips to the moon. Light was first stopped in 2001 for a fraction of a second. Earlier this year, researchers kept it still for a record 16 seconds using cold atoms. To break the minute barrier, George Heinze and colleagues at the University of Darmstadt, Germany, fired a control laser at an opaque crystal, sending its atoms into a quantum superposition of two states. This made it transparent to a narrow range of frequencies. Heinze’s team then halted a second beam that entered the crystal by switching off the first laser and hence the transparency. The storage time depends on the crystal’s superposition. A magnetic field extends it but complicates the control laser configuration. Heinze’s team used an algorithm to “breed” combinations of magnet and laser, leading them to one that trapped light for a minute (Physical Review Letters, doi.org/m86). They used the trap to store and then retrieve an image consisting of three stripes. The feat could enable a quantum repeater, which would stop and then re-emit photons used in secure communications, to preserve their quantum state over long distances.
Would-be fathers, your sperm clock is ticking IT’S not just women who have to worry about their ticking reproductive clock. Men’s sperm quality seems to deteriorate after the age of 35. The proportion of sperm carrying an X chromosome also seems to increase, meaning older dads are more likely to have daughters. It has been controversial whether the quality and quantity of a man’s sperm deteriorates with age. “However, there is fairly convincing epidemiological evidence that older men do find it harder to conceive a child –
regardless of female age – and as men get older their partners are at increased risk of miscarriage,” says Allan Pacey, a fertility specialist at the University of Sheffield, UK. There is also a slightly increased risk of older men fathering children with genetic disorders. To investigate, Bronte Stone at Reproductive Technology Laboratories in Los Angeles and his colleagues analysed sperm samples from 5081 men aged between 16 and 72. They found a deterioration in sperm quality and quantity after age 35. Some
previous studies had suggested that the decline doesn’t start until around five years later (Fertility and Sterility, doi.org/m85). “Whether it’s 35 or 40, the message from this and other papers is that men should be aware of age-related changes in their reproductive system and if they wish to become fathers they shouldn’t leave it too late,” Pacey says. The study also found a decrease in the ratio of Y to X-bearing sperm once men hit 55, though it is not clear why. Paulo Ricardo de Oliveira Roth
Light stopped for a whole minute
Alive! We survived a post Toba winter NO ARK required. Animals survived the flood of lava that erupted from the Toba supervolcano about 74,000 years ago just fine on their own, a new genetic analysis shows. The finding casts doubt on the theory that humans were almost wiped out around that time by a “volcanic winter” – an idea that comes from genetic data showing that the population rapidly expanded just after that time, as if it had recently collapsed. If Toba caused such a collapse, humans would not have been the only ones affected, reasoned Geoffrey Hayes of Northwestern University in Chicago. His team examined the DNA of 19 mammal species from every continent looking for a similar genetic pattern. It showed up in seven of them, but only coincided with Toba in two – the Siberian roe deer and Chinese black snub-nosed monkey. The results are not proof: Toba might still have devastated the human population, Hayes says, but it is another piece of evidence against it. The work was presented at the Society for Molecular Biology and Evolution meeting in Chicago this month.
Tiny heir of the sabre-toothed cats COULD this little guy be the best living representative of the extinct sabre-toothed cats? If so, the South American short-tailed opossum could help us understand how the iconic predators used their teeth. Despite being just 10 centimetres long, the short-tailed opossum is aggressive and will attack larger mammals. Ernesto Blanco at the University of the Republic in Montevideo, Uruguay, and colleagues made skull measurements on four of the opossums, along with 40 other South American marsupial predators. They then compared the results with
corresponding data on the skulls of extinct sabre-toothed animals. The opossums’ canines are much larger relatively than those of the other living animals in the study, and their jaws open unusually wide. Their bite is relatively weak, as modelling suggests was true of sabre-toothed cats. Blanco suggests opossums may be evolving along similar lines. He adds that their large teeth probably evolved to attract mates (Journal of Zoology, doi.org/m89). The clouded leopard has also been touted as a living analogue of the cats, but is little studied as it is so rare.
27 July 2013 | NewScientist | 19