A test you take alone is never only about you.
Turi King is the geneticist who identified the bones found under a Leicester car park as Richard III. Her book runs from a single accidental discovery in a British lab in 1984 to the present, and it is a genuine history of a field rather than a tour of curiosities — though it has plenty of those too, from horsemeat to Dolly the sheep to dinosaur DNA that was not dinosaur DNA.
Your genome is shared property. You simply happen to be the one holding it. The Mdrn Urban
to the ethics of CRISPR.
DNA tells you what you are predisposed to. It does not tell you what will happen, and the gap between those two is where most of the trouble lives.
A king under a car park, identified by a distant cousin.
King led the genetic work that confirmed the remains found in Leicester in 2012 belonged to Richard III, who died in 1485. The method is worth understanding because it is the whole book in miniature: you cannot identify a skeleton from its DNA alone, only by matching it to somebody living. That meant tracing a maternal line down more than five centuries to living relatives and comparing mitochondrial DNA. Identification is always relational. There is no absolute reading of a genome, only a comparison, and the comparison requires somebody else.
The technique that freed a man before it convicted one.
The field starts with Alec Jeffreys — King’s own mentor — who in 1984 was looking at something else entirely when he noticed that certain repeating regions of DNA varied enough between individuals to act as an identifier. Within a few years it was in the courts, and the detail worth remembering is the order of events: in the first criminal case to use it, the technique cleared a young man who had already confessed, and only afterwards identified the actual killer. Forensic genetics arrived proving an innocent person innocent, which is the correct frame for everything that follows.
Four different inheritances, four different questions.
King is unusually good at explaining the machinery without diluting it. Mitochondrial DNA passes down the maternal line essentially unchanged, which makes it excellent for deep ancestry and useless for identifying an individual. The Y chromosome does the same along the paternal line, which is why it tracks surnames in many cultures. Autosomal DNA recombines every generation, which makes it the right tool for close relatedness and the wrong one for anything ancient. And the markers themselves — short tandem repeats for forensics, single-letter variants for traits and disease — answer different questions again. Most public confusion about DNA testing comes from applying one of these to a question that belongs to another.
Cold cases solved by somebody else’s curiosity.
The most consequential development of the last decade is forensic investigative genetic genealogy: rather than matching a crime-scene sample to a suspect, investigators match it to distant relatives in consumer ancestry databases and then build a family tree downward until only one candidate remains. It has resolved cases that were closed for forty years. It also means that the decision to spit in a tube is not an individual one. A cousin you have never met can make you findable, and nobody asked the rest of the family. King lays out both sides carefully, because this is a genuinely hard problem rather than a slogan.
Consent in genetics is structurally broken: the only person who can give it is never the only person affected.
The Mdrn UrbanIt is in your dinner and in the wildlife trade.
Some of the most enjoyable chapters have nothing to do with murder. Animal DNA testing is how the horsemeat scandal was exposed, and it is routine food-fraud enforcement now — the same logic that verifies what is in a beef product verifies what species a piece of timber or a shipment of fish really came from, which makes it a conservation tool as much as a consumer one. The same techniques settled the fate of the Romanovs and punctured a run of famous claims about ancient DNA, including the dinosaur sample that turned out to be contamination. The through-line is that genetics became infrastructure while the public was still thinking of it as a plot device.
Eugenics is not a closed chapter.
King does not treat the ethical material as an appendix, and the book is better for it. The history of eugenics sits in the middle of the discipline, not before it, and the questions it raised return in modern clothing every time a technology makes selection cheaper: embryo screening, predictive risk scores, CRISPR editing of a germ line that has not consented to anything. Her position on the individual question is clear and worth carrying — a predisposition is a probability, not a sentence, and the distance between a BRCA1 variant and an outcome is filled with medicine, environment and choice. The harder question is collective: who gets to decide which variations are worth preventing.
A predisposition is not a destiny.
That is the sentence King builds the whole book toward, and it cuts in two directions: it is a comfort to anyone holding a worrying result, and a warning to anyone tempted to treat a genome as a verdict on a person. The second use is the dangerous one, and it is the one history keeps repeating.
Summarised in my own words from The Secrets of Our DNA: How Genetics Has Changed the World by Professor Turi King (Penguin / Michael Joseph, 2025). Twelve chapters, fully referenced and indexed. Nothing here is medical advice.