American Scientist

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

Listening to Balzac

A new analysis of clinical-trials data suggests that antidepressant drugs are a lot less effective than most people think. Indeed, the study indicates that they work better than placebo treatment only for the most severely depressed patients. But wait—the results are even more depressing than that: The relative value of these drugs for the severely depressed arises only because such patients do not respond very much to placebo treatment, not because anti-depressant drugs are inherently more effective with this population.

Kirsch, I., B. J. Deacon, T. B. Huedo-Medina, A. Scoboria, T. J. Moore and B. T. Johnson. Initial severity and antidepressant benefits: A meta-analysis of data submitted to the Food and Drug Administration. PLOS Medicine 5(2):e45 (February)

Oh the Things You Can Find

"My goodness! My gracious!" they shouted. "It's new! It's something outrageous! An elephant-shrew!"

Although the elephant-shrew may seem like an invention of Dr. Suess, it is, in fact, a real animal. And a species of this genus (Rhynchocyon) has just caught the attention of the scientific community. The other three species of Rhynchocyon were first described in the 19th century, so finding a fourth species now comes as a pleasant surprise, one that well demonstrates the biological richness of the Udzungwa Mountains of Tanzania, where this creature first appeared in camera-trap images in 2005.

Rovero, F., G. B. Rathbun, A. Perkin, T. Jones, D. O. Ribble, C. Leonard, R. R. Mwakisoma and N. Doggart. A new species of giant sengi or elephant-shrew (genus Rhynchocyon) highlights the exceptional biodiversity of the Udzungwa Mountains of Tanzania. Journal of Zoology 274:126-133 (February)

What a Long, Strange Trip It's Been

A group of physicists has proposed that the first stars to form after the Big Bang may have been nothing like those decorating the night sky today. These investigators suggest that the early universe may have been populated by huge "dark stars," which contained hydrogen and helium but were powered by the annihilation of dark matter instead of by nuclear fusion. Their moniker notwithstanding, such bodies may have been luminous and thus might one day be detected in sensitive telescopic surveys looking into deep space and past times.

Spolyar, D., K. Freese and P. Gondolo. Dark matter and the first stars: A new phase of stellar evolution. Physical Review Letters 100:051101 (February 4)

The Sound of the Furry

The fossil record of bats extends back 50 million years. But until now it has been unclear whether bats evolved their echolocation abilities before or after having taken to the air. A new fossil find from the Green River Formation of Wyoming suggests that flight came first. This primitive bat species,Onychonycteris finneyi, has wing elements similar to other bats, but its cochlea is smaller than that seen in extant echolocating bats.

Simmons, N. B., K. L. Seymour, J. Habersetzer and G. F. Gunnell. Primitive Early Eocene bat from Wyoming and the evolution of flight and echolocation. Nature 451:818-821 (February 14)

Plucked from the Past

Paleontologists who study the evolution of flight in birds (rather than bats) have been struggling to fill in gaps in their knowledge of how feathers developed over time. What they know about ancient forms has come mostly from fossilized impressions left in fine-grained sediments. But far more detail is now available from a stunning recent find—a set of seven Cretaceous-age feathers encased in amber (fossilized tree sap). It's unclear, though, whether these plumes, which come from an amber deposit in western France, represent an early bird or a non-avian dinosaur.

Perrichot, V., L. Marion, D. Néraudeau, R. Vullo and P. Tafforeau. The early evolution of feathers: Fossil evidence from Cretaceous amber of France. Proceedings of the Royal Society, Biological Sciences. (Published online February 19)

Enough to Give You the Bio-Willies

A new study suggests that when land is put into cultivation to produce biofuels, so much carbon is released from the soil that the net effect is to boost carbon dioxide in the atmosphere for many decades, perhaps even centuries. For example, conversion of central grassland in the United States to the production of corn ethanol produces a carbon debt that is calculated to last 93 years. And the conversion of tropical rainforest to agricultural land to produce soybean biodiesel creates more than three centuries of carbon debt. So, ironically enough, biofuels produced on converted lands end up putting more carbon dioxide into the atmosphere for long periods than would using the equivalent amount of fossil fuel. Oops.

Fargione, J., J. Hill, D. Tilman, S. Polasky and P. Hawthorne. Land clearing and the biofuel carbon debt. Science 319:1235-1238 (February 29)

Into Each Rain Some Life Must Fall

It has been known for decades that cells wafted into the atmosphere can serve as the nucleation sites for the ice crystals that form inside clouds—crystals that eventually fall to the ground as rain or snow. But some recent work has helped to quantify just how common this phenomenon is. The investigators gauged that frequency by examining samples of freshly fallen snow collected from various sites around the world. DNA-containing cells proved to be ubiquitous, although they constituted less than 1 percent of the total number of particles found in the snows tested.

Christner, B. C., C. E. Morris, C. M. Foreman, R. Cai and D. C. Sands. Ubiquity of biological ice nucleators in snowfall. Science 319:1214 (February 29)