It’s tempting: Take a DNA test and find out where your ancestors are from… and maybe connect with some long-lost relatives. It’s certainly quick and easy. Just run a cotton swab along your cheek or spit into a container and send if off in the mail. But does it work?

Yes. And no.  Genetics has come a long way in terms of accuracy (and falling prices). But it is still an inexact science. 

Consider the case of the identical twins who recently took DNA tests. Since twins have virtually identical DNA, you’d think they would get the same results. But no, according to an investigation by the Canadian Broadcasting Corporation, which reported that their test results varied widely. The conclusion: Across the industry, estimates of where an individual’s ancestors lived can differ significantly from company to company. 

Part of the problem is that for the most part, our ancestors didn’t stay put. As they moved around, leaving their genetic imprints wherever they procreated, they made it increasingly difficult for geneticists to distinguish one region’s population from another’s.

The good news

Even if the results aren’t always perfectly accurate, DNA tests can be interesting – and pretty much on target. Stories abound about adoptees finding their birth families and others successfully determining their ancestral origins – often with a surprise or two, which is part of the fun.

According to a reporter for Science News, 23andMe and AncestryDNA “were the most fun to use.” But her conclusion was that if you’re really interested in tracing your ancestry, consider DNA tests as a fun place to start. They can “kick-start a genealogy hunt, but combing through marriage certificates, military rolls, census records, immigration documents, old photographs and other records — which can provide — is what really tells me who my ancestors were,” the reporter wrote.

The scoop on DNA health testing

The same science reporter sent off samples to several testing companies to see what she could find out about her health. Her conclusion: “Overall, none of these genetic testing companies give you complete information about your health and genetics. Veritas may give you the most bang for your health care dollar, but its report is definitely not as user-friendly as 23andMe’s.”

If you’re interested in DNA testing for health purposes, it’s always a good idea to a genetic counselor to explore your options. Then, if the testing produces something to worry about, it’s time to talk to a doctor. Also, keep in mind that testing for health is more expensive.

About those twins and their funky results

Discrepancies in DNA testing don’t mean genetic science is a fraud. They just show that science still has a way to go. Think of it this way: The companies that provide ancestry information are precise in their ability to read customers’ DNA. The challenges come in how they choose to interpret that information. As an example, the tests are looking for evidence that you have common ancestors with people in the certain reference group. But the reference group each company uses can be different. That’s why one company’s ancestry results might look a bit different from another’s.

Another limitation: These reference groups are largely based on people who are self-reporting their ancestry. These people may be pretty confident that they know where their families come from, but it’s not a perfect measure. For example, until recently 23andMe was limited to matching people to only three broad regions in sub-Saharan Africa. That is a huge area with a lot of geographic and ethnic diversity. Why was 23andme limited? Because there aren’t as many African people in its geographic data. 

What’s more, the computer programs have to make some guesses about how far back in time your ancestors in a particular place lived. This also is imperfect, with a range of error. 

The bottom line? If you’re curious, have fun with it

Since the ancestry focused genetic tests usually cost from $60 to $100, you’re not going to be out a ton of money. Just remember, you are who you are, no matter what the tests say.