Tundra Reveals Oldest DNA

Scientists from Denmark, England and Russia have detected DNA from plants that lived 300,000 to 400,000 years ago -- the oldest DNA ever found -- in core sediment samples from 100 feet deep in the Arctic tundra. The finds were especially surprising, they reported, because much of the DNA was not found in the remains of specific plants or animals, but was simply preserved in the frozen ground. That suggests that scientists need not be limited to studying fossil remains as they try to unravel the genetics of early evolution and discern what the ancient environment looked like.

Many of the ancient plant DNA samples, buried in frozen soil and Siberian ice in the region near today's Bering Straits, are from a gene involved in photosynthesis. Fragments were found from a variety of plants, including mosses, herbs, shrubs and trees.

Eske Willerslev of the University of Copenhagen and his team also found animal DNA sequences that appear to have come from woolly mammoths, steppe bison, reindeer, musk ox, lemmings, hares and horses. The fact that so many of those animals were large herbivores suggests that much of the DNA had once been part of the rather prodigious loads of dung the animals produced.

By dating various samples and comparing their prevalence, the researchers were able to determine how the landscape changed thousands of years ago -- documenting, for example, that the ratio of herbs to shrubs declined through the Pleistocene epoch and that sedges overtook grasses around the peak of the last glaciers, 22,000 to 16,000 years ago. Similar studies in New Zealand caves provided evidence of a number of extinct birds and other animals.

"This demonstrates that sedimentary genetic signals of plant and animal communities can be preserved for considerable periods, in both permafrost and temperate conditions," the scientists report in Science Express, the online version of the journal Science.

-- Rick Weiss

Consequences for Bullies

There's more evidence that childhood bullying can have serious consequences, for both the bullies and their targets.

Federal researchers, funded by the National Institute of Child Health and Human Development, analyzed the results of a survey of 15,686 students in grades 6 through 10 in public and private schools.

Children who either had bullied others or were bullied themselves were much more likely to engage in violent behavior, such as carrying a weapon, fighting and being injured in a fight, they found. Bullies, however, were more likely than their victims to engage in this behavior.

Of boys who said they had bullied others at least once a week in school, 52.2 percent had carried a weapon in the past month, 43.1 percent carried a weapon in school and 38.7 percent were in frequent fights. Among boys who said they were bullied, 36.4 percent had carried a weapon, 28.7 percent carried a weapon in school and 22.6 percent said they frequently had fights. Of boys who had never bullied others, only 13.4 percent carried a weapon, 7.9 percent carried a weapon in school and 8.3 percent often fought.

"Bullying should not be considered a normative aspect of youth development," the researchers wrote in the April issue of the Archives of Pediatric Adolescent Medicine, "but rather a marker for more serious violent behaviors, including weapon carrying, frequent fighting, and fight-related injury."

-- Rob Stein

Telescope Grounded Again

NASA's newest space telescope, a $1.2 billion infrared observatory 20 years in the making, has been grounded for another four months -- until mid-August, NASA announced Friday -- because of possible problems with a booster nozzle.

It will cost NASA about $30 million, or $2 million a week, to store the Space Infrared Telescope Facility, or SIRTF, in a pristine "clean room" at Cape Canaveral until after the launchings of two Mars rovers June 6 and June 25.

SIRTF, the fourth and final member of NASA's "Great Observatories" program, was scheduled for launch April 18. The flight was put on hold the week before because of concern about delamination in the carbon composite layers in one of the nine solid-fuel boosters strapped to the first stage of SIRTF's Delta 2 rocket.

NASA managers decided Friday to ground SIRTF until mid-August after determining it would not be possible to replace the suspect booster without risking a delay in the high-priority flight of the second Mars rover, which will depart from the same launch pad.

Boeing engineers now plan to "destack" SIRTF's Delta 2 and to begin assembling a new Delta 2 rocket for the Mars Exploration Rover mission. The boosters slated for use in the Mars mission have been given a clean bill of health.

SIRTF was delayed to mid-August to avoid any conflict in case of problems that might delay the second Mars launch.

-- William Harwood

Tundra in Siberia has produced DNA samples from plants that lived 300,000 to 400,000 years ago.