Island's History in DNA / Micronesian population shows influence of 19th-Century western sailors

TALK ABOUT a long-lasting signature: Whaling crews who

visited the remote and tiny Pacific island of Kosrae almost two centuries ago

are still evident there-in genetic terms.

Analysis of the present-day islanders' genes show that once the sailors

rowed themselves ashore, commingling-as it were-with the island's people, the

Caucasian Y chromosome entered the Micronesian population and stayed there.

Today, as much as 10 generations later, about half of the island's males stem

from those Caucasian lineages, some of them American, scientists report.

According to molecular geneticist Jeffrey Friedman, when the first

westerners arrived in 1824, their visit wasn't much of a blessing. By the end

of the century, the original population of 2,000 to 3,000 Micronesians had been

decimated by diseases, and fewer than 300 still occupied the beautiful island.

By then, about 100 Caucasians, mostly men, had married into the population.

"Our data seems to support the idea that half of the genes are Caucasian,

and the rest are Micronesian," Friedman said during a recent meeting on human

origins held at the Cold Spring Harbor Laboratory.

Among the Caucasian visitors, Friedman told his audience, was one sailor

known as "the pirate," who was especially adept at fathering children.

Today, the population of Kosrae has grown to about 7,000 people, and the

island is now one of the Federated States of Micronesia. According to Friedman,

the local economy is growing as the tourist industry expands, catering

especially to scuba diving enthusiasts from Australia.

Friedman's interest in Kosrae stems from his longtime research into the

genetic basis of obesity. In fact, Friedman and his colleagues at The

Rockefeller University in Manhattan discovered the gene that makes leptin, a

potent agent that the body uses for weight control. Their discovery opened the

door to a better understanding of mammalian control of body fat. The complex

problem of obesity is what drew Friedman to the tiny island, Kosrae. Being

grossly overweight is a major problem for people who live there, in part as a

consequence of eating a fat-rich diet, and perhaps also because they are

genetically pre-disposed to obesity.

The diet problem is obvious. Because of a long-standing agreement with the

U.S. government for the use of territorial waters, the people of Kosrae receive

a constant supply of U.S. food. But Friedman said most of what they get is

Spam, other meats, fats, and an inordinate number of turkey tails.

"The turkey tails are a real delicacy there," Friedman said. Even though

turkey tails are not much favored in the United States, the people of Kosrae

have learned to love them, in spite of the gristle and a large amount of fat

they contain.

Because a fatty diet is combined with a propensity for weight gain,

Friedman said, "obesity is rampant" among the islanders. Compared to the United

States, where the average body mass index is 25, the average on Kosrae is 30.

Anything much above 25 is considered unhealthy, overweight, if not obese.

Researchers have speculated for years that some native populations-the Pima

Indians of Arizona are the best-known example-carry a so-called "thrifty gene"

which allows them to store energy as fat, a defensive mechanism to see them

through lean times. The problem for such people is that the "lean times" have

disappeared, while their fat-storage ability keeps on working overtime.

So the combined result of a rich diet and extra-efficient use of food

becomes a huge excess of body fat. And along with the fat come all of the

complications that accompany obesity, including heart disease, high blood

pressure and diabetes.

In an effort to sort out what's going on-and maybe even find the "thrifty

gene"-Friedman spent a week on Kosrae in 1994, in collaboration with the

island's department of public health. Together, they did physical examinations

and took blood samples from 2,200 people.

Next spring he's going again, flying first to Hawaii, then catching the

long island-hopping flight that stops in Micronesia and other island groups

before going on to Guam. Once he gets to Kosrae, Friedman hopes to continue the

genetic screening program, adding 2,000 more people to the study.

He emphasized that all of the people who participate are fully informed

about what's going on and are asked to sign consent forms in both languages,

Kosraen and English. It's important, he said, that the people of Kosrae are

aware of the results and how the data will be used in research.

"Next time around, we're going to stay a longer time," Friedman said,

because there is so much to be done. He finds the people in dire need of

greater health care resources. "They don't really have any access to medicine,"

he said.

Based on the research done so far, Friedman said, the evidence suggests the

thrifty gene resides on human chromosome 1. The new research may help narrow

the search further.

In addition, the combined studies of all the people sampled should paint a

bigger picture, helping the research team identify which parts of the

islanders' genomes came from Caucasians and which were already there with the

original Micronesians.

Knowing which genes came from which sources may also allow the scientists

develop analytical tools for use in other situations, letting them track

disease genes through the intricate puzzle known as the human genome.