On the horizon

Measuring wind potential

If only 20 percent of the Earth's "wind-power potential" were tapped, humanity could meet all of its electricity demand seven times over, according to a new study.

Two researchers at Stanford University's Department of Civil and Environmental Engineering set out to provide the first hard estimate of the number of sites with commercially exploitable wind flows. The team used data from more than 8,000 weather stations and balloon-sounding sites around the world to estimate the number of places that could host stands of turbines 260 feet tall and generate enough electricity to be cost-effective.

At least 13 percent of the sites had annual average wind speeds faster than 15 miles per hour at the height of a turbine blade's hub - enough to make a commercial go of wind power.

North America boasts the largest number of potential sites. Other areas with high potential include Tasmania, the southern tip of South America, and northern Europe. The two note that remote areas that lack weather observations could add to these numbers.

The duo acknowledges, but does not address, the environmental and other hurdles that would need to be cleared to realize wind power's full potential. Their results are set to appear in a future edition of the journal Geophysical Research-Atmospheres, published by the American Geophysical Union.

Born to sing

Canaries have long been prized as songsters. Now scientists are discovering that aspects of what canaries sing as adults are innate, not learned. More surprising, adult birds can switch from uncanary-like phrases learned as youth to more-structured adult phrasing, much as humans can rapidly switch from speaking French to English and back.

Biologists from the United States and Switzerland isolated male hatchlings, reared them in soundproof chambers, and exposed them to random or glissando tones that lacked distinct patterns in adult canary songs.

The tykes took up these tones and repeated them with ease - until they began to reach sexual maturity. At that point, the researchers found that the still-isolated birds rephrased the songs they'd learned into passages typical of adult birds reared in the wild.

As adults, many of the team's birds not only sang in the more natural patterns, but they also quickly switched between early songs and mature songs, much as a multilingual human switches languages. The team speculates that these similarities suggest common neural mechanisms for tapping and ordering "learned vocal units." The team reported its results in the current edition of the journal Science.

Man's first travels

Go North, early man - or was it South? Questions about the direction early humans took as they trekked out of Africa between 55,000 and 85,000 years ago have long lingered among anthropologists. Now, two teams working independently appear to strengthen the case for the southern route - across the Red Sea and along the Indian coast to Southeast Asia and Australia.

The alternate route, along the Nile, across the Sinai Peninsula, and up the Levant to the rest of the world, remains a possibility.

But researchers have had a tough time explaining why modern humans taking that route would end up in southern Australia thousands of years before they replaced Neanderthals in Europe.

The teams used maternal DNA sequences, known as mitochondrial DNA, as biological clocks. The samples were taken from indigenous people living in the Andaman Islands and on the Malaysian peninsula. The DNA taken from the modern Andamanese appear to have directly branched from the DNA of a "founder" population that arrived some 65,000 years ago.

DNA from the Malaysian group suggests that their forebears branched from other Asians 60,000 years ago. One team uses the data to infer that a population of several hundred individuals migrated east at up to 2.4 miles a year. They reported their results in the current edition of the journal Science.

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