It is far too late to completely protect your genetic privacy via personal abstention. A brief exploration into the mathematics of genetics explains why it has become possible to track down killers—but also anyone—through distant relatives.
“If somebody wanted to use the skills of forensic genealogists to try to track you down through a third cousin, they could,” said Jennifer King, a privacy scholar at Stanford University.
To understand how exposed your genes potentially are, consider an obscure unit of measurement—the centiMorgan, or cM.
It gauges genetic distance, specifically the length of identical segments of DNA that two people share due to descent from a common ancestor.
In general, people have about 6,800 cMs. A child inherits half their DNA—one set of chromosomes—from each biological parent. So child and parent will have around 3,400 cMs of DNA that match.
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Even with all these halvings, very distant relatives out to fifth cousins share so much identical DNA that a common ancestor is the only possible source.
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There is no such thing anymore as truly anonymous sperm or egg donors, unknown fathers, or closed adoptions. They are all examples of scenarios where secrets involving parentage are easily solved by the centiMorgans.
