The Value of Being Anonymous

When faced with a threat, many people believe in the idea that there is “safety in numbers”. And in some situations, it makes sense that if you are trying to hide, it may be easier if you are in a group of 1000 as opposed to being in a group of just 10. However, when it comes to our DNA, pretty much the opposite can be true. With DNA, the bigger the numbers of individuals contributing to a collection (also known as a database), the easier it becomes to pick out one specific individual from the group.

This happens because we all share some of our DNA in common with other individuals, especially those that are members of our family. Brothers and sisters, for example, share (on average) about 50 percent of their DNA, and the same is true for parents and their children. If you have aunts or uncles, you will typically share about 25 percent of your genes with each of them. You will also share about half of that (12.5 percent) with any cousins (1st degree) you might have, and so on as you extend further out. In fact, if you know your ethnic makeup, you can think of all other members of that same group as members of your extended biological family. You will all share some of your DNA in common, but exactly how much depends on many factors. Regardless, all members of the same ethnic group will typically share more of their DNA than they would with a randomly chosen person that is not at all related.

Because of this, as you can imagine, if we want to track someone down using DNA, we begin simply looking in a database of  to find people that share some of their data in common. Shared data most likely means that individuals are related, and so the more that people contribute to a database, the more likely it is that we can find people related to each other. In other words, a database containing DNA from 100,000 people is much more likely to reveal closely related people than a database containing DNA from only 100. And, the more closely related people you find, the easier it becomes to narrow the search down to just one – that is, to you. According to one source, if just two percent of the people in a population put their DNA in a database, there is about a 99 percent likelihood that you will be able to find one particular person.

Just how big are the databases that are currently available? Some years ago, the government of Iceland decided to get  information from all of its people. Currently, about 150,000 Icelanders, about half the population, have their information in a database. A study recently published used information from 500,000 individuals with their DNA in the UK Biobank. Another study used information from 1.28 million people that put their information into companies that do consumer genetic testing.

These numbers are so large in part because many people want to be found using their DNA. It can be a great way to find long lost cousins or other members of your family, or just people that share the same ethnicity. However, if for example the information in a database is linked to information about your health status or risk for developing a disease, you may not want to be easily identified. This may make it more difficult for you to obtain medical insurance or a life insurance policy. However, you may also want to have this kind of information as long as you can keep it to yourself.

This basically leaves you with two choices: One, you can never put your DNA into a database, or two, you can put it into a database but do everything possible to ensure that you remain anonymous to everyone else to protect your identity. The choice is yours.

By David Haymer, Professor of Genetics, University of Hawaii

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