While the latest discoveries in genetic science show that variations among ethnic groups are, essentially, only skin deep, there are subtle differences. Medical researchers think different chromosomal notes in the human genome symphony will soon help save lives through what is being called personalized medicine.
Evolution has helped humans adapt to their surroundings. Some in Africa carry a mutation for blood cells that increases resistance to malaria but also makes people more susceptible to sickle cell anemia. Many adults from ethnic groups that did not domesticate dairy animals early on - a geographically diverse group including Japanese, many African groups and Ashkenazi Jews - lack an enzyme to digest milk. But the condition is rare among Scandinavians and Bedouins, both traditionally dependent on milk from their herds.
Physicians say they are acutely aware of how people respond differently to medication. Some people metabolize drugs faster than others - and that can critically affect dosage.
In North America, patients who have suffered a heart attack and are prescribed the blood-thinning drug Warfarin usually receive a daily dose of 10 to 15 milligrams. But Japanese doctors say that is too much for their patients. Here, they are more likely to get between one and 10 milligrams of the medication.
Two patients with the exact same condition, age and body weight may respond completely differently to drugs. Dr. Norihiro Kato, head of gene diagnostics and therapeutics at the Japan International Medical Center, says this leads to a dangerous and costly trial-and-error method of medication.
"Yeah, this can kind of phenomena is very famous and most of the clinicians know that. It is not economical," he said. "I mean redundant prescription is currently required."
Researchers say the reason for many differences appears to be genetic. Scientists at the Japanese research institute Riken and Tokyo University have discovered four genes they say will allow doctors to more accurately prescribe drugs that keep blood from clotting.
The researchers in Japan are part of what is called the International HapMap Project, which includes scientists and agencies in Britain, Canada, China, Nigeria and the United States. It collects DNA samples and analyzes chromosomal locations, known as loci, to identify and catalog genetic similarities and differences in human beings.
Dr. Yusuke Nakamura is the director of Tokyo University's Human Genome Center and head of the HapMap project for Japan.
"We basically examined more than one million loci, which are likely to show the differences, among the individuals, among the races," he said. "Also those differences basically reflect the difference among the ethnic groups or among races."
Sixty-six Japanese hospitals are participating in the project. At the Human Genome Center, samples of DNA from 115,000 people are kept in what is called a biobank. The number eventually will nearly triple, allowing custom-made treatment for the people who gave the samples.
In Fukuoka, Japan, scientists at Kyushu University's Research Center for Genetic Information analyze samples taken from Japanese donors, while teams in Beijing, Shanghai and Hong Kong delve into the DNA of ethnic Han Chinese.
Kenshi Hayashi, professor of genome analysis at Kyushu University, says their discoveries will be significant for medicine in Asia. "We found that the two ethnic groups are very close," he said. "So [I'm] almost certain that one drug that is effective in Chinese should be also effective in Japanese."
A commercial device, invented by a team led by Dr. Nakamura in Tokyo, goes on the market next year and will allow doctors to check genes to determine how a patient is likely to respond to an individual drug. The test will take an hour and a half, and cost about $50.
Dr. Nakamura says such equipment in the future will test a range of drugs at one time and be even more affordable. "Maybe 10 years later, 20 years later, we can examine a set of the genes associated with drug efficacy or drug adverse reactions," he added. "And that makes diagnosis much cheaper. Basically, the patient should keep their genetic information in the IC [integrated circuit] card and bring it to the hospital."
To some critics this research raises the specter of eugenics - weeding out genetic traits or types of people deemed inferior. Others fear that such tests could allow employers or governments to discriminate against some people because of a genetic tendency toward particular diseases.
Researchers say societies will need to set rules for how and when such testing is used.
Dr. Nakamura at Tokyo University thinks that fears about misuse of genetic research are overblown, pointing out that when it comes to DNA, no one is flawless. "We all have six or seven kinds of mutations related to the genetic diseases," he said. "So we should learn that nobody is perfect."
Some physicians predict that despite the concerns, their colleagues will embrace personalized medicine, seeing it as a kind of insurance policy against deadly medical errors.