How many lineages can an American have at most?

Brent Kennedy was born in the Appalachian Mountains in the 1950s. He always thought that, like everyone in his hometown Wise County, Virginia, he was descended from England, Scotland and Ireland. It was not until 1962 that he saw the movie Lawrence of Arabia that he found that his family was more like Arabs in the movie. Kennedy inherited his father's light blue eyes, but he also inherited his mother's black hair. In summer, his skin will be tanned.

Last year, in 65438+February, Kennedy spent 199 dollars to do a genetic test at DNA Print Genomics Inc in Sarasota, Florida, and finally got some answers. He is 45% of northwest European descent, 25% of Middle Eastern descent, 25% of Turkish-Greek descent and 5% of South Asian descent.

More than 654.38 million Americans have taken pedigree genetic tests provided by commercial laboratories. There are many celebrities among these people, such as talk show queen oprah winfrey and director Spike Lee. Are you Native American or African descent? Are you related to people with the same surname? By scraping cell samples from the mouth, genetic testing will answer a series of questions. The cheapest price for these tests is $95. Among them, the latest service was launched by the National Geographic Society in April this year. It can help you understand the history of ancestors' migration, and at the same time fund a five-year survey project aimed at depicting the migration route of modern humans.

The results of the experiment will bring emotional shock to many people, especially those who are adopted, descendants of slaves and others who know little about their ancestors. Of course, some people question its accuracy. Hank grilli, an ethicist and lawyer at Stanford Law School, said: "When genetics becomes a commodity for consumers, it is oversimplified and exaggerated." Although it is relatively simple to determine whether a person is African or Asian, it is much more difficult to be accurate, for example, whether he is African Ivory Coast or Asian Sri Lankan. As the genealogy database obtains more samples, the accuracy can be improved. However, on the global question of "who am I", many American immigrants and mixed-race children will be happy even if they only know a rough answer.

Special attraction to African-Americans

Behind the DNA test, many scientists hold the view that modern humans who evolved in Africa 65438+ ten thousand years ago are all over the world, during which genetic mutations occurred. The researchers tried to confirm the time and place of various mutations.

They tracked these mutations and compared them with the samples in the DNA marker database. These samples were selected from thousands of people with special geographical background. If individual mutations are consistent with these native populations, it is possible to establish some kind of connection.

Genetic testing is particularly attractive to African-Americans because most of them have no other way to trace their ancestors. The slave trade cut off their roots in Africa. From Hausa people in northern Nigeria to Ashanti people in Ghana, African Ancestry, a gene tracking company in Washington, hopes to re-establish the connection between them by telling customers whether their lineages match some of the hundreds of African ethnic groups.

For Juanita Thompson, a real estate agent in Arlington, Virginia, this test means a lot. Because her mother was adopted when she was a baby, she knew nothing about the family where she was born. "I always feel a sense of emptiness." Thompson, 6 1 year-old, said, "But the genetic test has taught me about my mother's family. This feeling is very good. "

Thompson was told that his mother's ancestors were Yoruba people in Ghana, Africa, and she was very satisfied. But it is this accuracy that has been criticized by critics. Bruce Jackson, a geneticist at the University of Massachusetts at Lowe, USA, is the director of the African-American Genetic Roots Project, a non-profit research aimed at finding out the genetic history of black Americans. He believes that it is still too early to classify ethnic groups. "Every ethnic group in Africa is mixed, and we haven't figured it out yet."

Rick Kittles, director of African-American science, defended the genetic test done by his company. He said that there are more than 20,000 gene samples in the database for comparison with customers' genes, which were selected from nearly 400 African ethnic groups. He also pointed out that only when the statistical probability exceeds 90%, the company will come to the conclusion that the bloodline is consistent. "I do the same thing as others. Just because my genetic testing is aimed at people of African descent, I am responsible. " Kittles said. He added that 3,000 people did the experiment and the price was $349.

Complete the genealogy

Another less controversial function of gene pedigree is to help people complete pedigree. Leo Little is a retired engineer in Austin, Texas, USA. Through the historical records of his family, he traced back to Thomas Little, and his great-grandfather was born in Alabama on 18 16. Then he said, "I hit a wall." Later, he found three distant relatives after genetic testing in genealogical DNA. Through family records, cousins trace their roots to 1680.

Although members of small families are willing to share genetic information, some people are worried about unauthorized sharing. Genetic testing companies said that they would keep the test results confidential, but at least one of them, DNA Mapping Gene Company, asked customers to sign a consent form, acknowledging that the test results "may lead to litigation".

Others complain that some of the most common tests only show the ancestors of one branch. For example, the Y chromosome tracks only one of the paternal lines (the father of the father's father, but the mother without the father). Similarly, mitochondrial DNA testing can only find out the maternal ancestors of mothers.

Of course, these defects in genetic testing have not stopped amateur genealogists like Charles Kirchner. The retired electrical engineer said that he spent about $3,000 testing the genes of himself and his nine distant cousins to confirm the connection between them that has been confirmed by family records. Is it worth it? "Of course. It's like a high-tech Bible entry. " Kirkner said. Tracing the roots with family records has exhausted the 60-year-old Kirkner. He said, "My only hope is genetic testing."