Science
Notebook

Monday, June 11, 2007

Arrow Felled Otzi the Iceman

Otzi, the 5,000-year-old frozen hunter found in a melting glacier by hikers in the Italian Alps, died from blood loss, shock and a heart attack caused by an arrowhead that severed an artery beneath his left collarbone. The arrow was pulled out, causing additional internal bleeding.

European researchers, who used the kind of three-dimensional computer imaging common in hospitals to avoid invasive procedures, said they have settled the debate about whether Otzi died from a fall, from freezing in the high mountains or from a wound. According to the analysis published in the Journal of Archaeological Science, the chances of surviving an arrow wound like Otzi's would be only about 40 percent today.

The frozen remains were found in 1991 and quickly became an international sensation. The cold preserved the man's body and the clothing he was wearing, which was made of deer and goat hides and included a bearskin hat and boots stuffed with straw. He carried a copper ax and flints to make fire.

Otzi is believed to have been a hunter or warrior who was killed in a fight with rivals. An analysis of four blood samples found previously on his clothes and weapons established that the blood came from four other individuals, suggesting that Otzi may have been in a spirited fight.

The high-resolution computer tomography used to examine his internal wound is frequently used in hospitals but is rarely used by archaeologists.

-- Marc Kaufman

Why Behavior Varies in Species

Some squirrels are timid, and others will snatch popcorn from your hand. One bird spoils for a fight around the birdbath, and another turns away from confrontation.

Such differences in behavior among individuals of the same species are evidence that animals have personalities, some scientists believe. Last week, two researchers from the University of Groningen in the Netherlands and another from Stockholm University argued in the British journal Nature that personality differences in animals are a reflection of evolutionary strategy.

They said that personality is shaped by the animal's timetable for reproduction. Using complex mathematical simulations, the researchers considered two theoretical individuals, each of whom lives for two years and can reproduce at the end of each year. The animals' environments vary in the quality of resources. One animal spends lots of time exploring to find the best food and habitat, investing in future reproductive success. The other explores more superficially and quickly, a strategy that emphasizes current reproduction.

The simulation showed that the thorough explorer, who expects to have a good chance to reproduce later, would behave in a more risk-averse way. The superficial explorer, living more for the moment, would behave more boldly.

Superficial explorers "evolve high levels of aggression in both games, whereas thorough explorers evolve to be consistently non-aggressive," the researchers wrote. The central principle in the shaping of animal personalities, they write, is that "the more an individual has to lose, the more risk averse it should be."

-- Christopher Lee

Low Testosterone, Shorter Lives

Men who have lower levels of testosterone may be at greater risk of dying early, according to new research.

A study of nearly 800 California men ages 50 to 91 found that those with the lowest testosterone levels had a 33 percent greater risk of death during the next 18 years than the men with higher levels.

"The new study is only the second report linking deficiency of this sex hormone with increased death from all causes over time and the first to do so in relatively healthy men," said Gail Laughlin of the University of California at San Diego School of Medicine, who presented the findings last week at a meeting of the Endocrine Society.

Testosterone levels tend to decline with age but vary widely, with many older men still having levels typically found in younger men. Low levels in the study were considered those at the lower limit of normal for young men.

The men in the study with low levels also tended to have more signs of inflammation, which has been associated with a variety of health problems.

Although the study might support the idea that taking testosterone supplements may benefit some men, the researchers cautioned against jumping to that conclusion. Lifestyle changes, such as losing weight and exercising, may work just as well and be safer.

"We are excited about these findings, which have important implications, but we are not ready to say that men should go out and get testosterone to prolong their lives," said Elizabeth Barrett-Connor, who helped conduct the research.

-- Rob Stein