Thank you, George Lopez! I am beyond delighted that George Lopez has decided to get on the genetic genealogy band wagon. DNA tests to learn about one's roots have been available for about a decade, but most are still unaware of this, so I applaud his decision to boldly ask celebrity guests who come on Lopez Tonight to open wide and swab. Not surprisingly, most demur, but to date, Larry David, Jessica Alba, and Lopez himself have all scraped the inside of their cheeks to take a peek into their pasts, and each time, awareness of DNA testing for purposes other than solving crimes and identifying baby-daddies grows.

If you haven't caught any of the genetic reveals, here's Lopez learning about his own results from his Mariah Carey. She wasn't keen to participate, but as another person "of mixed lineage," was game to be the one to introduce him to his past.

For those who are new to genetic genealogy, I should point out that there is no magic, instant roots DNA test. In fact, there are a handful of different kinds of tests. The one being used on Lopez Tonight is autosomal. Most genealogical DNA tests can only shed light on a single branch of your family tree, but autosomal ones offer a broader picture, providing some sense of your overall heritage. Typically, such tests break your heritage into continental chunks, telling you roughly what percentage African, Asian, European and (sometimes) Native American you are.

For a variety of reasons, results of autosomal tests should be taken as an indication, not an absolute. First, percentages being presented are those calculated to be the most likely; they are not definitive! Remember confidence ranges from your high school or college stats classes? Plus or minus X percent? These come into play. Three percent Asian, for instance, might just be statistical noise. Similarly, eight percent African might really be eight percent African, but it could also be, say, 11 percent or two percent when the whole range of possibility is taken into account.

Also, we have so many ancestors that the genetic echoes of any one ancestor get washed out over time, so someone taking an autosomal test hoping to find proof of that Cherokee princess so many families claim is apt to be disappointed. Even setting aside the fact that there's no such thing as a Cherokee princess (more on that and other popular myths another time), many of us who do actually sport some Native American ancestry had it introduced into the family centuries ago - probably too long ago to show up in results today. In most of us, our ancestral pool of the last four or five generations will essentially out-shout earlier genetic contributions.

Finally, these tests are based on genetic variations called SNPs (Single Nucleotide Polymorphisms), and according to genetic genealogy expert, Dr. Ann Turner, "There are virtually no SNPs that are one hundred percent informative for ancestry - always found in one continent and never in another." [Full disclosure: Dr. Turner and I are co-authors of Trace Your Roots with DNA.] The ideal would be to have SNPs that are only found in those of African heritage, for instance, but it's a little more complicated than that. Autosomal tests offered today are based on dense, genome-wide scans which allow us to investigate combinations of multiple SNPs - and that leads to my one quibble with what Lopez Tonight is doing. They're using outdated testing (based on individual SNPs).

While the particular test the show is using was once the best (and for a long time, the only) available for ancestral purposes, newer ones based on far more thorough scans are considerably more accurate. To put it into perspective, taking this kind of test today is a bit like listening to music on a cassette player instead of an mp3 player. Those of us who like to play with DNA are scratching our heads about why a 2005 product is being used when it's practically 2010.

When Larry David responded as if his 37 percent Native American results were a joke, his instincts were correct. The best known quirk of the test Lopez Tonight is using is its problem distinguishing between Asian and Native American (understandable, given that if you go back far enough, Native Americans originate from Asia), but a lesser known quirk is its tendency to assign Native American percentages to many of Iberian, Italian and Ashkenazi heritage - and Larry David is Ashkenazi. Sorry to burst any "imagine that!" bubbles, but more sophisticated testing would likely produce significantly different results.

So George, are you really 55 percent European, 32 percent Native American, nine percent Asian and four percent African? Maybe, but I have my doubts. This same test pegged me as eight percent Native American and six percent African, which is curious, given that I'm half-Irish/half-Slavic and most of my family has only been in America for three or four generations. More current testing identified me as one hundred percent European - admittedly blander, but certainly more credible for someone of my ancestry.

I truly am grateful to Lopez Tonight for shining a spotlight on genetic genealogy and I hope the show will continue to encourage its guests to take DNA tests, but please, call me so I can save you some serious backpedaling down the road! I'll even spring for your retesting, George!