American Scientist

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

Ground Zero 1908?

On June 30, 1908, an immense explosion in the atmosphere leveled a huge tract of the Siberian wilderness and sent seismic and pressure waves careening around the world. Scientists have surmised that the "Tunguska event," as it is called, resulted from the impact of a small asteroid or comet with the Earth, the body exploding several kilometers above the ground where it released at least the energy of a 10-megaton nuclear bomb. This interpretation of the event is still a matter of debate, in part because no fragments of an extraterrestrial body have been found. But now a team of Italian investigators may have pinpointed where something solid hit the ground: a crater, which now holds a body of water called Lake Cheko.

Gasperini, L., et al. A possible impact crater for the 1908 Tunguska event. Terra Nova 19:245-251 (August)

I Love New York

New York City in part owes its reputation for callousness to a sad episode that took place there in the 1964: A young woman named Catherine ("Kitty") Genovese was brutally stabbed to death near her home in Queens while 38 people stood by, failing to come to her aid—or so the story goes. A recent investigation by three psychologists reveals this description of uncaring New Yorkers to be an urban myth. The investigators found that 38 people had not, in fact, witnessed the stabbing, that those who witnessed the crime did not see the murder taking place and that some people at the scene did indeed attempt to help. Start spreadin' the news. . .

Manning, R.,  M. Levine and A. Collins. The Kitty Genovese murder and the social psychology of helping: The parable of the 38 witnesses. American Psychologist 62:555-562 (September)

Marathon Mouse

The enzyme phosphoenolpyruvate carboxykinase is present in a variety of mammalian tissue types, including the kidney, liver, small intestine, colon, mammary gland, adrenal gland, lung and muscle. Biologists understand the role of this enzyme in the kidney and liver, but they have been perplexed by what exactly it does in these other tissues. To help solve that riddle, a team of investigators from Ohio created a transgenic mouse with the gene for this enzyme linked to a promoter that is active in skeletal muscle. In this way, they spawned a line of mice that produce much greater than normal amounts of this enzyme in their skeletal muscles. And the result is quite amazing. Whereas a normal mouse typically runs 200 meters when placed on a treadmill, the transgenic mouse they engineered can run a full 6 kilometers. This marathon mouse eats 60 percent more than normal mice, but it weighs half as much and has only 10 percent of the body fat. What's more, this transgenic phenom has an extended lifespan—and seemingly a good one at that. The team reported that transgenic mice that are as much as two and a half years old can run twice as fast as normal mice that are only six months to a year old. Eat your Wheaties, maybe, but don't forget your phosphoenolpyruvate carboxykinase.

Hakimi, P., et al. Overexpression of the cytosolic form of phosphoenolpyruvate carboxykinase (GTP) in skeletal muscle repatterns energy metabolism in the mouse. The Journal of Biological Chemistry 282:32844-32855 (November 9)

He Ain't Heavy, He's My Cousin

In evolutionary terms, people are quite closely related to other great apes. Our connection with monkeys and other primates is slightly more distant but still pretty clear. How primates are related to other taxonomic groupings has remained somewhat muddled, however. But an analysis of genomic data has now revealed that the closest living relatives to primates are colugos, also known as flying lemurs, which are squirrel-sized creatures that inhabit the rain forests of southeast Asia. The genetic evidence suggests that the divergence between the two groups took place during the Cretaceous period.

Janečka, J. E., et al. Molecular and genomic data identify the closest living relative of primates. Science 318:792-794 (November 2)

Thanks for the Lift

Although many people are familiar with Yellowstone's geysers and hot springs, few realize that the area underwent several cataclysmic eruptions not all that long ago—as geologists measure time. Some 640,000 years ago, a giant eruption left a volcanic crater (or in geologist lingo, a caldera), which measures about 50 kilometers across. Smaller eruptions took place in the region only 70,000 years ago. And the place hasn't exactly settled down yet. Geodetic measurements reveal that the Yellowstone caldera began a rapid episode of ground uplift in mid-2004, rising at rates of as much as 7 centimeters per year. Modeling suggests that molten rock is rising from deep within the Earth and filling a magma chamber that sits about 10 kilometers below the caldera.

Chang, W.-L., R. B. Smith, C. Wicks, J. M. Farrell and C. M. Puskas. Accelerated uplift and magmatic intrusion of the Yellowstone caldera, 2004 to 2006. Science 318:952-956 (November 9)

Why Did the Ungulate Cross the Road?

Many people's connection with large wild animals is limited to seeing these creatures browsing by the side of the highway. In some spots, particularly in protected natural areas, the abundance of such animals at the roadside is substantial, leading a person to think that more distant reaches of the forest must be awash in such fauna. In fact, the opposite may be true. It seem that some wild animals prefer to spend time close to people, roads and cars, precisely because predators are apt to avoid these locales. This dynamic is true at least for moose, which gravitate to roads so as to avoid run-ins with bears. Now, if they can avoid all the Jaguars, Cougars, Rams, Vipers and Impalas, they should be reasonably safe.

Berger, J. Fear, human shields and the redistribution of prey and predators in protected areas. Biology Letters 3:620-623 (December 22)