DNA is “not love,” notes a woman in “The Lost Family,” a new book about consumer genetic testing. Disappointed to learn that a man she thought was her half brother wasn’t after all, she was underscoring that reality as revealed by DNA may not match reality as actually experienced in families. This idea surfaces repeatedly in Libby Copeland’s well-researched exploration of the consequences — intended and otherwise — of Americans’ increasingly common practice of sending saliva samples to companies like 23andMe and AncestryDNA. The growing and assertively marketed industry then gives customers information about their background and allows them to find relatives by comparing their DNA with that of others in the companies’ databases.For many, the results help flesh out family trees they already recognize. Others, including people adopted as children or conceived with donor sperm, can resolve longstanding questions about their birth parents. But some receive shocking surprises, like an “NPE,” shorthand for “non-paternity event” or “not the parent expected” — revelations that one’s mother or father is not who the person thought they were. “The Lost Family” explains the rise of the consumer genetics industry and how “search angels” — citizen-scientist genetic genealogy experts — devote hours to helping “seekers” solve DNA mysteries.Copeland reiterates a few central questions throughout the book: “How much of your sense of yourself should scientists and algorithms be allowed to dictate?”; “What makes us who we are?”; and “Is it always better to know the truth?” Of course, the answers are up to the individual reader and will vary based on things like family dynamics and how earthshaking the consequences of knowing might be. Copeland’s balanced treatment of the subject allows readers to reach their own conclusions and shows them many of the factors they might consider as they do.There’s a section on the pros and cons of companies’ ability to share consumer genetic information with researchers and pharmaceutical companies — which could lead to better medical treatments, but also to a host of privacy issues. For instance, genetic ancestry databases to solve cold criminal cases, a practice that’s taken off since it helped identify the notorious Golden State Killer.Copeland also discusses the slipperiness of genetic ethnicity estimates, which are much less precise than the matching of individual family members. A test result might categorize someone as 37 percent Scandinavian or Irish, but as companies’ reference databases expand and their algorithms sharpen, such estimates could shrink or grow. The databases are also lopsided, containing more samples from people with European backgrounds than those with African or Latin American ancestry.The book describes the controversial history, and future potential, for genetic information to be misguidedly conflated with racial and ethnic categories, even though science has documented more genetic differences within distinct population groups than between them. Attempts to twist genetic information to draw boundaries between groups have seeded societal toxicities like eugenics and white nationalism. And even people lacking nefarious motivation can blunder by linking genes and heritage too closely, Copeland writes. She cites the criticism of Elizabeth Warren’s assertion that her 2018 DNA test suggesting she likely had at least one Native American ancestor six to 10 generations ago supported Warren’s longstanding belief, based on her family’s stories, that she was part Cherokee and Delaware Indian.“The Lost Family” intersperses expository sections with an intermittent narrative of the step-by-step journey of Alice Collins Plebuch, a woman who is thrown for a loop when AncestryDNA results contradict her impression that her forebears were Irish, English and Scottish. Readers might find the unfurling of Plebuch’s story a bit too attenuated, but her eventual discovery illustrates the hidden history that genetic testing can uncover.Copeland drops in stories of other people who ferreted out family secrets. For some, like the man who learned his grandfather was African-American, not Italian, the information adds richness and context to their lives. For others, like the woman who received a letter from a lawyer asking her to stop contacting her biological father, or the woman whose half siblings wanted nothing to do with her, the denouement can be painful.“DNA testing reveals a truth that is black andwhite, even if the circumstances are gray, and then, everybody has to grapple with it,” Copeland writes. Still, she says that anecdotes suggest most people are glad they unearthed the facts, even if the consequences were difficult. Hopefully, that’s true because, the book contends, so many Americans are sending spit samples to DNA databanks that many genetic nuggets will inevitably be surfaced — whether people want to keep them buried or not.