American Scientist

This roundup summarizes some notable recent items about scientific research, selected from news reports compiled in Sigma Xi’s free electronic newsletters.

Closing in on Early Life

The diversity of life may have evolved from a single-celled ancestor—but whence the original self-replicating cell? One theory has it that the versatile RNA molecule was the original replicator that led to higher levels of metabolism. But today, cells use both DNA and proteins to build new RNA. If RNA were the founding molecule, it would have to replicate without help. And indeed it can, say scientists who created a system of two RNA enzymes that copied one another—and evolved—in a test tube. The pair increased in abundance 100 million fold in just 30 hours, with no signs of burning out. Now, to get the works into a cell.

Lincoln, T. A., and G. F. Joyce. Self-sustained replication of an RNA enzyme. Science (published online January 8)

Mirror Shade-glasses

The brownsnout spookfish (Dolichopteryx longipes) haunts murky ocean waters hundreds of meters deep. In this dusky setting, it and other species evolved upward-facing eyes that soak in light from above. But that leaves a dangerous blind spot to the sides and below. In some fish, extensions from the main eyes help fill the visual void by detecting, but not focusing, reflections and bioluminescence from other directions. But the spookfish has even more impressive optics, recently discovered in the first study of a live specimen. Its downward eye-extensions do focus light—using a crystalline mirror, something never before found in a vertebrate eye. Because mirrors absorb less light than lenses, the spookfish’s “extra eyes” not only see in focus, they do so without wasting photons in the light-starved scene.

Wagner, H., et al. A novel vertebrate eye using both refractive and reflective optics. Current Biology (published online December 24)

Impact Diamonds

At the end of the Pleistocene, there was a catastrophe on Earth. It caused more than a millennium of global cooling, disappearance of the North American Clovis culture, and extinction of mammoths and other mammals. In 2008, a team of scientists controversially invoked the impact of a fragmented comet to explain these phenomena. The notion gains strength this year with the documentation across North America of nanodiamonds in sediment that dates just prior to the mass extinction. Nanodiamonds—nanometer-sized particles of diamond dust—may form in the pressure of an impact or arrive on Earth clinging to extraterrestrial bodies.

Kennett, D. J., et al. Nanodiamonds in the Younger Dryas boundary sediment layer. Science 323:94 (January 2)

Pouting Pooches

A sense of fairness informs decisions among cooperating humans, chimpanzees, capuchin monkeys—and now dogs. When experimenters worked with a pair of dogs, rewarding one, but not the other, for performing a “hand shake,” the uncompensated dog eventually refused to participate. And it wasn’t just the lack of bread and sausage: Control dogs working alone without treats still did the trick 50 percent more often than shortchanged dogs who witnessed their partners rewarded. A similar sense of justice is likely to occur in other species that engage in group hunting or other collaborative behaviors.

Range, F., et al. The absence of reward induces inequity aversion in dogs. Proceedings of the National Academy of Sciences 106:340–345 (January 6)

First Aid in the Chalcolithic

More than 5,000 years ago, a 46-year-old man now known as Ötzi the Tyrolean Ice Man perished in the Alps, probably from head trauma and an arrow wound. Now, in an intestinal analysis of the ice mummy, researchers have found six species of moss in Ötzi’s gut. He probably ingested the plants accidentally with drinking water, or when he used them to wrap food and bandage wounds. One species, a Sphagnum moss, has antimicrobial properties and was a likely wound dressing that Ötzi could only have obtained in boggy areas far from his final resting place. Either he set out with a first aid kit of moss, or he hiked some 60 kilometers in the final few days of his life.

Dickinson, J. H., et al. Six mosses from the Tyrolean Iceman’s alimentary tract and their significance for his ethnobotany and the events of his last days. Vegetation History and Archaeobotany 18: 13–22 (January)

Graphene is Growing

Graphene, a single layer of carbon atoms arranged in a neat honeycomb pattern, conducts electrons with remarkable speed. The bendy, stretchy material may eventually replace silicon as a semiconductor in solar cells and electronics, and could drive new flexible electronic gadgets. So far, it has been impossible to make enough high-quality graphene—but methods are catching up to imagination. It is now possible to produce square centimeters of graphene using carbon-containing vapors to deposit the film on a thin nickel base, then dissolving the nickel. Warning: Computers may start to bounce back when punched in frustration.

Kim, K. S., et al. Large-scale pattern growth of graphene films for stretchable transparent electrodes. Nature (published online January 14)

A Game of Cat and Rabbit

Macquarie Island, located halfway between Australia and Antarctica, is a World Heritage site. It was once a haven for penguins, petrels and other seabirds. But introduced domestic cats and rabbits have ravaged the island for decades: Rabbit-control efforts in the 1960s forced the cats to eat seabirds, so ecologists then targeted the cats. Cat control, in turn, has allowed the rabbit population to explode since the late 1990s. Despite a virus introduced to help control rabbits, the animals’ population has increased by about 4,000 per year. The resulting overgrazing and erosion spell even bigger trouble than cats for Macquarie’s beleaguered seabirds.

Bergstrom, D. M., et al. Indirect effects of invasive species removal devastate World Heritage Island. Journal of Applied Ecology 46:73–81 (January)