DNA Testing Companies: What They Can and Cannot Reveal about Your Ancestry

With the advent of consumer genetic testing, family secrets are becoming increasingly harder to keep under wraps. There are fewer and fewer skeletons remain safely locked in the closet. For encouraged by genetic companies' promise to shed light on dark moments in their histories, people have started spitting in a tube and sending away their DNA samples with boundless enthusiasm. 

Around 30 million of them have taken a genetic ancestry test so far, and their appetite to determine their consanguinity with others or track down their ancestry seems only be whetted by the improvements that genetic companies demonstrate in their DNA research. Last year, the number of tests taken by people surpassed sales of all previous years combined, and 2019 promises to be equally busy for genetic companies. More and more people seem willing to uncover new information about themselves, their relatives, and their distant ancestors. 

If you share the desire to learn more about your roots, you can turn to one of the companies that provide different genealogy and heritage DNA tests. Some of them are voted to be better than others and provide more precise information than their competitors. But before you choose one of these companies, there are several factors you need to know about the genetic testing so that you do not entertain false expectations about the information that you can receive.

Indeed, often people become disappointed in test results not so much because they find out unpalatable truth about their family members but because they simply have wrong understanding of what these tests can or cannot tell them about their heritage. Even though the science has remarkably advanced, the information genetic testing companies present to people is often only general and approximate. Genetic testing companies simply cannot provide the degree of exactness that people expect from them when they send them their saliva or buccal swab. 

There has been much confusion about the DNA results received by siblings, for example. The internet is full of stories about siblings that get different reports from genetic testing companies. When this happens, people either start suspecting their parents of infidelity to each other or simply criticize the company for incompetence. What they fail to understand, however, is that DNA tests tell how much of their ancestors' DNA people inherited. They also do not realize that siblings can inherit different pieces of DNA. Indeed, even though their ancestors are exactly the same, siblings can inherit from them a dissimilar DNA makeup.

If, say, you have a Chinese ancestor, you may inherit his or her DNA, of which any genetic company will surely inform you. But your brother might not inherit any piece of DNA from your Chinese forefather and will receive a report where will be no mention of his Chinese ancestry. The difference in your and your brother's genetic reports is not the reason to suspect that he was adopted or sired by a different father. Chances are that your Chinese ancestor merely did not leave a trace in your brother's DNA but managed to pass his genetic code to you. It is useful to remember in this regard that genes are always passed on unequally to further generations. 

When they send the samples of their DNA to genetic testing companies, people also imagine that their genetic reports will determine an exact ratio of different ethnicities in their blood. They expect, too, that once these ethnicities are established, researches will tell them with unerring precision where their ancestors were located. But genetic tests have no means to provide such information. The problem is that our ancestors were nomads, wandering through vast geographical territories and mixing with each other. Due to this mobility, contemporary scientists cannot distinguish a population of one region from a population of another region. 

What further minimizes the reliability of scientific conclusions about our roots is that companies analyze people's genetic makeup by comparing their DNA to the samples of the individuals living today rather than to the samples of former generations. In other words, scientists draw the map of the ancient world by analyzing our present population and applying to this analysis their knowledge of earlier migrations. It well may be that the conclusions they draw about the locations of ancient people are justifiable. But people should always bear in mind, when they are told that their ancestors lived on the territory of the modern-day Italy, for example, that researches are only guessing and may be seriously erring about their ancestors' geographical location.

Even if researchers are correct in identifying particular ancestors in people's families, they do not indicate from which side - paternal or maternal - these ancestors came down to them. The information people receive is, therefore, highly general, since genetic tests rely mostly on autosomal DNA, which carries information inherited from both parents.

Suppose you read in your report that you have some Indian ancestry. Having done the autosomal test that studies a mixture of your genes inherited from your father and mother, you will have no way to know from which side your Indian ancestor descended to you. Each of your parent can have a full-blown Indian forefather. If you want to dig deeper and find out who is responsible for the genes passed on to you from your Indian ancestor, both of your parents would need to take the DNA test. Without additional tests, your knowledge of your roots will remain vague and incomplete, though often even your parents' DNA tests would not shed the brighter light on your ancestry.    

There are other expectations that people have and that DNA testing companies cannot fulfil. It is thus useful not to trust their advertisements unconditionally and learn what the genetic science can or cannot tell you about your genes before you set out to find the truth about your distant or recent past.