Letters from the September 3, 2005, issue of Science News

Pick of the crop

“Honey, We Shrank the Snow Lotus: Picking big plants reduces species’ height” (SN: 7/9/05, p. 20) suggests that the change is an evolutionary process. However, this and the other examples given are all more selective breeding than natural selection. In this case, organisms with undesirable characteristics (smaller size) are overrepresented during reproduction as the result of removing the larger organisms from the breeding population.

Robert Ardrey
Prescott, Ariz

The tale of the snow lotus certainly has aspects of selective breeding, but in this case, human influence makes a species less desirable to people rather than more so. And remember that “evolutionary process” is a broader term than “natural selection.” To quote the researchers in their study’s abstract, “Humans can unconsciously drive evolution… .”—S. Milius

Why wait?

I was very glad to read of the research done by Stefano Pluchino with adult-mouse stem cells (“Brain Power: Stem cells put a check on nerve disorders,” SN: 7/16/05, p. 36). I am, however, terribly disappointed with his comment that therapeutic trials in humans are 4 to 5 years away. As someone with multiple sclerosis and a scientific background, I see no reason why the timetable can’t be moved up.

Lauri Riley Dowling
Valley Glen, Calif

In our interview, Pluchino, of the San Raffaele Scientific Institute in Milan, Italy, suggested that researchers need 4 to 5 years to know whether adult neural stem cells will have anti-inflammatory effects in people, not that it will take 4 to 5 years before a human trial to determine that will start.—N. Moreira

Light reading

“Bright Future: New materials and devices bring white LEDs closer to home” (SN: 7/16/05, p. 43) makes a comparison: “A LED can last for up to 100,000 hours compared with the 1,000-hour lifetime of a typical lightbulb and the 10,000-hour lifetime of a typical fluorescent lightbulb.” This is misleading in comparing the maximum LED lifetime with typical bulb lifetimes. The typical lifetime of an LED depends on the application. LEDs for flashlights are often advertised at only 10,000 hours, yet there are long-life incandescent bulbs rated at 20,000 hours. Rating bulbs is complex.

Steve Wilson
Safety Harbor, Fla

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