The mathematics are inescapable. The higher the altitude, the less oxygen the air will hold, and the more difficult it is to breathe. Either the body adapts or the person dies.

For decades scientists accepted an "Andean man" model for acclimatization: The body at altitude will grow a higher concentration of oxygen-absorbing red blood cells to mop up scarcer oxygen from rarified air.

Add bigger lungs and deeper breathing, and equilibrium is re-established. The result is a blocky fellow with a washtub chest, like the musicians who play the panpipes and wooden flutes of Andean mountain music.

"Their lungs are 25 percent bigger than ours," said Case Western Reserve University anthropologist Cynthia Beall. "Andean highlanders are very distinctive."

Earlier this month, however, Beall and five colleagues reported on another distinctive people -- a community of Ethiopians who live at 11,650 feet, and whose blood, by several common measures, is exactly the same as if they lived at sea level.

"I'm flabbergasted; I don't see how they do it," said exercise physiologist David Martin of Georgia State University. "I'm left with a dozen questions. It's a fascinating kind of story."

And it is not just a curiosity. For Martin, a consultant for USA Track & Field, and others like him, the extraordinary success of African distance runners -- principally Ethiopians and Kenyans -- has been a source of wonder ever since barefooted Abebe Bikila won the 1960 Olympic marathon.

Is there a secret that others cannot possess?

"Efforts to find a genetic explanation have been dismal failures," said Dallas cardiologist Ben Levine, an expert in exercise medicine. "My personal opinion is that these successes are cultural. A distance runner in Ethiopia or Kenya is a national hero."

In an online article to be published in the Proceedings of the National Academy of Sciences, Beall's team reported on 300 people living in the Semien Mountains about 300 miles north of Addis Ababa.

Testing showed they had neither elevated red-cell concentrations nor low levels of oxygen saturation in their blood -- two key indicators of the Andean model.

"We were stunned," Beall said. "The Ethiopians are finding the same amount of oxygen we find, even though the amount of oxygen in the air they breathe is two-thirds of what we have at sea level."

Humans transport oxygen via hemoglobin, a protein in red blood cells that binds to oxygen molecules and moves them from the lungs to muscles and other tissues. At sea level, between 95 and 97 percent of the body's hemoglobin is saturated with oxygen during every breath.

At altitude, reduced oxygen logically means lower oxygen saturation. In the Andes, highlanders compensate by producing more red cells to create a heightened "hemoglobin concentration" -- a higher proportion of red cells in the blood. That way the blood has more hemoglobin to sponge up scarce oxygen.

Lowlanders need at least 10 days for this process to begin. In the meantime, however, they will acquire the other characteristic of high altitude survival -- deeper and more frequent breathing. The Andean barrel chest comes from being born and raised at altitude.

Scholars were satisfied with this explanation until studies in Tibet in the 1970s showed that highlanders there had both low hemoglobin concentrations and low oxygen saturation levels. In theory, the Tibetans should have been oxygen-starved.

"But they breathe faster, and there's also some evidence that they are better able to modulate blood flow," Beall said. "When they exercise, their blood flow increases more rapidly, so they may have a larger cardiac output. We don't really know."

The Himalayan research triggered a debate over a possible evolutionary explanation for high altitude adaptation.

The Andeans, whose lowland ancestors migrated from Asia perhaps 16,000 years ago, adjust to altitude essentially the same way as any lowlander would today -- and it is not a perfect solution.

"Creating more red cells is a pathological response," said Temple University anthropologist Charles Weitz. "If you have too many red cells, the blood's too thick, and it's like pumping oil. Eventually you have to move downhill."

Tibetans or their ancestors, however, have been in Asia for 1 million years or more -- time enough, some scholars theorize, to evolve a different approach.

From Mike:

This may well support my postural thesis as the Kenyans run like they were taking off from an airplane runway. Up, not forward, but UPward. I've always admired them as the best breathers. My vote would be posture, diet, lifestyle (including exercise), attitude. I suspect now that "PROGRESS" has discovered them that they will deteriorate rapidly.