American Scientist

This roundup of notable recent items about scientific research, culled from news reports, was compiled from free electronic newsletters produced by Sigma Xi.

The Solar System Loses One of Its Planets

The International Astronomical Union stripped Pluto of its status as a planet, reclassifying it as a "dwarf planet" under historic new guidelines. The newly adopted scheme also includes a third category of objects, "small solar system bodies" such as asteroids and comets. The decision was reached after days of debate among 2,500 astronomers at the union's general assembly—a debate that is not yet over. The list of astronomers in disagreement with the assembly's decision includes Alan Stern of the Southwest Research Institute, who calls the decision "sloppy science," and Harvard professor Owen Gingerich, chair of the definition committee, who implied that the decision was hijacked in a "revolt" by one subgroup.

http://www.washingtonpost.com/wp-dyn/content/article/2006/08/24/AR2006082400109.html

Gene May Explain Boost in Brain Power

Researchers have found a clue as to why human mental capacities are so much greater than those of chimpanzees. A gene that has undergone significant change in the human line since the two species split some 5 million years ago may partly account for the accelerated evolution of our brains. Although the investigators do not know exactly what the RNA product of this gene does, they believe it is active at a key time and place in embryonic development when the brain is growing at its fastest pace.

Pollard, K. S. et al. An RNA gene expressed during cortical development evolved rapidly in humans. Nature 443:167–172 (September 14)

Ozone Hole May Soon Shrink in Size

David Hofman and Susan Solomon, two scientists who had helped alert the world to the existence of a menacing hole in the stratospheric ozone layer above Antarctica, recently reported that this worrisome feature of the atmosphere appears to have stopped widening. After the hole was discovered in 1986, international agreements were reached to end the use of ozone-depleting chemicals (chlorofluorocarbons, or CFCs), and these measures may allow the hole to "heal" completely sometime over the next century.

http://news.bbc.co.uk/2/hi/science/nature/5276994.stm

Dark Matter Really Does Exist

After studying data from a long-ago collision of two giant clusters of galaxies, some astronomers claim that they have found proof that subatomic dark matter actually does exist and plays a central role in creating and defining gravity throughout the universe. For decades, scientists have theorized that much of the universe is made up of nearly undetectable dark matter and dark energy. Others prefer alternative interpretations. This latest finding will no doubt influence an active debate among physicists and cosmologists.

Clowe, D. et al. A direct empirical proof of the existence of dark matter. The Astrophysical Journal 648:L109–L113 (September 10)

Not a Newfound Human Species

A new study casts serious doubt on the proposal that the ancient bones of a diminutive hominid found two years ago on the Indonesian island of Flores represent those of an entirely new species of ancestral human. Scientists from Indonesia, Australia and the United States conducted a comprehensive analysis based on their own firsthand examination of the available bones, which include a single mostly complete skull. The evidence, they report, suggests that the enigmatic skull belonged to a pygmy human who suffered from a developmental abnormality.

Jacob, T. et al. Pygmoid Australomelanesian Homo sapiens skeletal remains from Liang Bua, Flores: Population affinities and pathological abnormalities. Proceedings of the National Academy of Sciences of the U.S.A. 103:13421–13426 (September 5)

Many Dinosaurs Yet to Be Discovered

Two-thirds of the world's fossil dinosaurs may still await discovery, according to a new statistical analysis. Paleontologists had identified 285 dinosaur genera between the early 1800s and 1990, but that number has since jumped to 527, an increase of 85 percent. This observation implies that the current fossil boom will likely continue, particularly as new lands are explored. The authors of the new study estimate the total number of "recoverable" genera at 1,844. They predict that 400 new varieties will be discovered in the next 30 years as paleontologists explore fossiliferous beds of appropriate age in China, Argentina and elsewhere in the world. The pace of new dinosaur discoveries should level off finally sometime in the 22nd century.

Wang, S. C., and P. Dodson. Estimating the diversity of dinosaurs. Proceedings of the National Academy of Sciences of the U.S.A. 103:13601–13605 (September 12)

First Tree Genome Sequenced

An international team of researchers has sequenced a tree genome. The four-year effort was the first of its kind. The black cottonwood, a variety of poplar, was chosen because it has relatively little DNA. It is hoped that sequencing trees can help the forestry industry to improve its products, including alternative fuels such as bioethanol. It may also be possible to engineer trees that can capture greater-than-normal amounts of carbon dioxide from the atmosphere.

Tuskan, G. A. et al. The genome of black cottonwood, Populus trichocarpa(Torr. & Gray). Science 313:1596–1604 (September 15)