MAMMOTH UNDERTAKING

It's long been a popular presumption that the woolly mammoth was hunted to extinction by early humans. Or, at the very least, people were a major factor.

But a new genetic study of fossilized mitochondrial DNA suggests the woolly mammoth population was not a single homogenous group, but two separate populations, one of which died out 45,000 years before the first humans appeared in the region.

The two groups were closely related, a surprise, given the mammoths' wide range, from Western Europe to the Bering Strait in Siberia to North America.

Such genetic closeness, say researchers at Penn State University, may have been the mammoths' eventual undoing.

"The low genetic divergence of mammoth may have degraded the biological fitness of these animals in a time of changing environments and other challenges," said biologist Webb Miller.

Modern-day elephants in southern India face a similar problem. Genetic diversity is so low among surviving individuals that conservationists are struggling to maintain a thriving population.

VERBATIM

The surest sign that intelligent life exists elsewhere in the universe is that it has never tried to contact us.

- Bill Watterson, creator of the comic strip "Calvin and Hobbes"

BRAIN SWEAT

Add the same letter seven times (with appropriate spacing) to the following string of letters, then respace the result to form four related words. You don't need to rearrange the letters in the string.

L A V I L E S A P U L A S A R U M O Y X

BRAIN SWEAT ANSWER

The letter added is C, forming the words: CLAVICLE, SCAPULA, SACRUM and COCCYX, which are four bones.

PRIME NUMBERS

19,200 - Number of described bee species (2,000 more than estimated just eight years ago)

100 - Minimum number of artifacts left behind on the moon by American astronauts, including a spacesuit worn by Buzz Aldrin

10,596 - Number of endangered Kemp's Ridley sea turtle hatchlings that successfully scuttled off into the ocean from Texas beaches last year, a record

35 - Number of the turtle hatchlings expected to reach adulthood

4 - Change since 2001 in percentage of Americans who believe mankind is causing climate change

Sources: American Museum of Natural History; Smithsonian; U.S. National Park Service; Harris Interactive

'TRUE FACTS'

Researchers at Japan's Keio University say experiments have shown that pigeons are able to identify themselves in video images and discriminate between the work of certain painters, such as Van Gogh versus Chagall.

Scientists say the pigeon's visual abilities exceed those of an average 3-year-old child.

BLOGOSPHERE

Good math, bad math

scienceblogs.com/goodmath/

Blogger Mark Chu-Carroll is a software engineer at Google. In his spare time, he "finds fun in good math while squashing bad math and the fools who promote it." That means lots of talk about things like linear programming, which isn't going to mean much to the numerically challenged.

But Chu-Carroll also talks about figuring out mortgages, stupid grading tricks and bad gas math.

QUIRKS OF NATURE

The Joshua tree is a distinctive yucca plant found primarily in the Mojave Desert, but its novelty doesn't stop there. According to University of Idaho scientists, specimens in the eastern part of the tree's range have evolved shorter stylar canals - the part of the flower that receives pollen - than specimens to the west. The reason, scientists say, has to do with the plants' primary pollinator: a kind of moth. Moths in the east have shorter appendages than those in the west.

WHAT IS IT? ANSWER

A bucketful of grenadiers or, less euphemistically, rattails. These are deep-water fish found in most of the world's oceans. There are 383 known species, ranging in size from 4 inches to 5 feet. They are abundant and may represent up to 15 percent of the deep-sea fish population. The larger species are commercially fished.

PATENTLY ABSURD

You know that old visual metaphor about life being akin to grains of sand running through an hourglass? Well, this is the digital version.

The "life expectancy watch," patented in 2002, basically counts down to your predicted death. It works according to actuarial data on factors such as whether you smoke, exercise, eat too much or have a family history of disease.

The purchaser is supposed to answer a series of questions about health and lifestyle, plugging the results into the watch, which then calculates how many years, months, days, minutes and seconds its owner has remaining.

It's adjustable, though. If the owner does something healthy, like exercising, he can temporarily turn the watch off. Presumably that means if you forget to turn it back on, you'll live forever.

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