Random Samples

Science  18 Aug 2006:
Vol. 313, Issue 5789, pp. 897


    Clay samples (above) drawn from a set of interconnected caves west of Sydney, Australia, suggest that the caverns may be 340 million years old, making them the most ancient accessible ones anywhere in the world. If the result holds up, the Jenolan Caves would be more than 200 million years older than the current record holder.

    Although dating caves can offer insights into geological history, it's also exceedingly difficult to accomplish. In part that's because the materials inside caves, and the stone from which they're made up, often predate the cave itself by millions of years. To date the Jenolan caves, which are a popular tourist destination, geologist Armstrong Osborne of the University of Sydney and his colleagues turned to clay considered a remnant of volcanic ash that helped the caves take shape, they write in the Australian Journal of Earth Sciences.

    The researchers estimated the age of the clay samples by comparing levels of radioactive potassium, which decays over time, to those of argon gas, which appears as the potassium decays. “The implication … that the caves formed by alteration of volcanic ash” is “entirely possible,” says Paul Renne, director of the Berkeley Geochronology Center at the University of California, Berkeley. Still, he's not convinced the clay didn't erode from preexisting rocks, although Osborne insists that's not the case.



    A veterinary anesthetic also favored as a rave drug is offering a glimmer of hope for treating depression.

    Ketamine, or “Special K” to clubgoers, improved the mood of 12 of the 17 depressed volunteers who received a single injection of it, Carlos Zarate, a psychopharmacologist at the U.S. National Institute of Mental Health in Bethesda, Maryland, and his colleagues report in this month's Archives of General Psychiatry. A placebo offered to the same group helped much less. The antidepressant effect lasted up to a week, but most exciting to pharmacologists was that ketamine started working in just 2 hours; typical antidepressants can take up to 2 months to kick in. Because suicidal behaviors are associated with the first days of standard therapy, that difference could prove critical.

    The study adds to mounting evidence that the brain's glutamate signaling system, controlled in part by the receptor hit by ketamine, is a specific target for depression therapies, says John Krystal, a psychopharmacologist at Yale University: “The glutamate story as it has emerged is very promising.”


    All out. In a major effort, divers killed this invasive alga before it spread out of control. CREDIT: RACHEL WOODFIELD, MERKEL & ASSOCIATES; INSET: GREIG PETERS

    There's not much good news about invasive species these days, so biologists were thrilled last month to declare victory in a 6-year, $7 million battle to rid the coastal waters of southern California of an exotic alga. “It's quite an achievement,” says ecologist Daniel Simberloff of the University of Tennessee, Knoxville, who was not involved in the effort.

    The enemy was Caulerpa taxifolia, a tropical species that has run rampant in the Mediterranean Sea, causing problems for commercial fishing, recreational diving, and pleasure boating. After it was discovered in two lagoons near San Diego in 2000, divers repeatedly searched every square meter of the murky waters (Science, 22 March 2002, p. 2201). They covered patches of Caulerpa with tarps weighted by sandbags and pumped in chlorine.

    Quarterly surveys have come up empty-handed since 2002. “We can say with 99.9% confidence that the Caulerpa is gone, so we declared success,” says Robert Hoffman of the National Marine Fisheries Service in Long Beach. “It feels great,” adds team member Lars Anderson of the U.S. Department of Agriculture in Davis, California. “We just hope we never see it again.”


    Police in the German city of Dresden are hunting for a rapist, and they're ready to collect DNA from up to 100,000 men to catch him. German police netted a killer in Cloppenburg in 1998 after 18,000 men were tested, but the Dresden effort could become the largest DNA dragnet ever performed in a criminal investigation.

    Dresden police devised the plan after finding identical genetic blueprints from sperm in two rape cases since last September. More than 3000 men so far have submitted to saliva swabs. Participation is voluntary, but the police acknowledge that those who refuse will be scrutinized, according to German media reports.

    “I think the strategy is worth it,” says Michael Brand, director of the Biotechnology Center at the Technical University in Dresden, even at its maximum cost of $3.5 million. The Dresden police have said publicly that after testing for a match, they will discard DNA from all men who do not have a serious criminal record, as the law requires.

    But “even if privacy is protected, to ask for DNA under threat of special scrutiny for those who do not cooperate may be coercive,” says Peter Lipton, a philosopher at the University of Cambridge, U.K. “Is this justified?”