On the horizon

Big hunters down under

Australian paleontologists have uncovered a wealth of new fossils that shed light on the demise of some of the continent's most remarkable animals some 40,000 years ago. The new finds help rule out changing climate as a leading trigger for their extinction, the team says, leaving open the likelihood that humans played a significant role.

Prior to humans arriving, Australia's "megafauna" included 10-foot-tall, 400-pound kangaroos and wombatlike animals that were more than six feet tall at the shoulders and weighed two tons. Researchers are still puzzling over why such creatures vanished.

Scientists found the fossils in caves beneath south-central Australia's Nullarbor Plains. The fossils – many of them whole skeletons – are so well preserved that the researchers say it is unprecedented in Australia. Among the finds: Eight new species of kangaroo, including two tree kangaroos. The diversity of the group, which the team dates to roughly 200,000 to 400,000 years ago, suggests that the region had more varied plant life than it does today. But several lines of evidence suggest that the region was dry, even then. This renders untenable the notion that these megafauna were vulnerable to arid conditions, the team says. Many of the species vanished by the time humans arrived or soon after. The report appears in Thursday's issue of the journal Nature.

In the 18th century, master paint mixer Heinrich Diesbach stumbled upon the color Prussian blue. Today, a team of French chemists might say: Thanks for the memory.

In the quest for more compact memory storage, researchers at the University of Paris have tweaked Diesbach's formula a bit and found that, when tickled with light, the pigment becomes magnetic and remains so until heated. Then it reverts to its nonmagnetic state. This ability to switch between two states is how memory devices store information. The team was able to image the modified compound and found that when red light struck it, the atoms in Prussian blue realigned in ways that led to the material becoming magnetic.

At this stage, the work is exploratory, and the material must be chilled to minus 238 degrees F. before red light magnetizes it. But it indicates the range of materials researchers are exploring as they try to shrink memory devices without sacrificing capacity. The work appeared in the journal Angewandte Chemie International Edition.

How does little Nemo determine his social standing in a school of fish? If scientists at Stanford University in California are correct, he uses logical inference, just as humans do.

The team found that tropical freshwater fish known as burtoni can figure out a pecking order among several potential rivals for food or mates, and rank them by observing how they fight other fish.

The team set up chambered tanks. It let one fish observe other fish fighting from a central cubicle. The scientists matched the pugilists so that the loser of the first bout would dominate the entrant in the second bout. Likewise for rounds two, three, and four. The team ensured that the lone spectator hadn't seen any of the fighters before, then repeated the experiment with eight other "observers."

Once the combatants had recovered, each observer swam in a three-compartment tank that let it move near either of the pair of former fighters. In nearly every case, the observer swam first to the weaker of the two former combatants and stayed with it the longest. The work appears in Thursday's issue of the journal Nature.