DNA Speaks

Besides its ability to settle paternity issues, DNA fingerprinting technology can also be used to help solve criminal cases, reveal the identity of corpses, track the progress of bone marrow transplant patients, and aid research on genetic relationships among and within ethnic groups.

These uses do not involve questions on whose child someone is, nor how valid a claim to a family's wealth or name is. However, their impact on humanity is likely even more profound.

Tracking transplants

DNA fingerprinting is used to track leukocyte count increases in leukemia patients who have received bone marrow transplants. In fact, this particular application is more commonplace than paternity testing.

Chen Pei-shan, a medical test technologist in Taipei Veterans General Hospital's Section of Transfusion Medicine, notes that the hospital's blood bank performs an average of more than 500 DNA fingerprinting procedures annually for bone marrow transplant patients, both those who just underwent the procedure and those whose long-term progress is being monitored. The DNA fingerprinting for bone marrow transplant patients generally only requires matching at nine DNA loci, making it far simpler than paternity testing, which uses 13 to 15 loci. If the result shows that the tested DNA is the marrow donor's genotype, this indicates that the transplant was successful. However, if a test shows a return to the patient's own genotype, the implication is that the transplant has failed or that the patient's leukemia has recurred.

It is also worth noting that paternity tests cannot be performed for marrow transplant recipients using blood samples, but rather must utilize cells from the mucous membrane in the oral cavity or from the hair. This is because the DNA present in the blood is from the donor.

In recent years, there have also been interesting developments in the application of DNA fingerprinting to tracing genealogies.

Based on his research on the Y chromosome, geneticist Chris Tyler-Smith of the UK's Wellcome Trust Sanger Institute has deduced that roughly 1.5 million people in north China and Mongolia are the descendants of the same man. After analysis, it is believed that this male ancestor was Giocangga, the paternal grandfather of Qing Dynasty founder Nurhaci. Scientists speculate that the numerous wives and concubines found in a Manchu royal court, as well as the regime's wide-ranging conquests, were helpful in spreading his genes.

In 2003, Tyler-Smith also co-authored a report entitled "The Genetic Legacy of the Mongols." From the finding that 8% of men in Central Asia and adjoining regions shared the same Y-chromosome segment, he and his colleagues surmised that these men too descended from a common ancestor. Matching this to the extent of the kingdom that Genghis Khan established in the 12th century and that spanned Europe and Asia, they concluded that Genghis Khan was an extraordinarily successful "procreator," with around 16 million direct patrineal descendants!

Although this research has proved controversial, with its accuracy as yet unconfirmed, it established a novel direction for research.

In addition, scientists studying human genetics at the UK's Oxford University have concluded after more than a decade of DNA research that most modern Europeans are actually distant relatives. 97% are descended from seven women who lived from 10,000 to 45,000 years ago. These seven ancient women consequently came to be known as Europe's "ancestral mothers." Scientists explain that for these women's mitochondrial DNA to be passed to on to generations living today, the seven not only had to survive to adulthood, but each had to give birth to at least two daughters.

Ancient relatives

Although scientists are sure of these findings, people living today feel very remote from ancient ancestors, making the scientists' claims lack immediacy. However, a recent discovery in the UK draws a connection between modern humans and the skeletal remains unearthed by archeologists.

When a scientist from Oxford's Weatherall Institute of Molecular Medicine was assisting in the production of a television program about archeology, he performed DNA fingerprinting on a 9000-year-old skeleton excavated from a cave, as well as on local residents. Unexpectedly, he found that the DNA from the skeleton matched that of a 42-year-old local history teacher, making them distant relatives.

An equally surprising discovery was made in a small town in Germany. While investigating a rape in which there were no clues except for semen left on the body of victim, the local police performed DNA tests on every man in the town. The results not only enabled them to apprehend the perpetrator, but also led to the discovery of a startling fact--15% of the fathers in the town were in fact raising children who were not their biological offspring.

As it happens, statistics compiled last year by a paternity testing center in Beijing showed that 15% of the tests resulted in paternity exclusion. In other words, 15% of fathers in Beijing were also unwittingly raising another man's child. Seen in this light, the number of such men may be roughly equal in Asian and Western societies, and the only substantive difference is people's attitude toward such an occurrence.

Scientists have found that all of humanity shares 99.9% of their DNA. Human and chimpanzee DNA differs by no more than 2%. However, such seemingly trivial disparities are enough to give every person a unique appearance, personality, and even destiny. And a series of dramas continue to unfold from the scripts encoded in DNA.