In the past 10 years, advances in genetic science have begun to reveal secrets to our identity that we never before knew. Now, through a simple swab of the cheek or basic blood test, we can learn about thousands of years of our genetic history, the genes behind our physical traits and even our propensity for certain diseases.
But unlike some other scientific advances, many of these new technologies are headed straight for the consumer market, pitched by companies such as Knome, 23andMe, Family Tree DNA and deCode. The promise, proponents say, is that widespread genome mapping will result in better, more-personalized medical care.
Some tests let users learn about their ancestry through their mitochondrial DNA, prompting some surprising -- and often shocking -- discoveries that have changed their personal identities. (In the most well-known case, Henry Louis Gates Jr., a prominent Harvard professor...