Early in the morning of April 29, 1945, in the final days of World War II, with the Allies closing in on the Führerbunker in Berlin, Adolf Hitler and Eva Braun exchanged marriage vows in which they declared that they were of “pure Aryan descent and not infected with inheritable disease which would exclude them from marriage.”Hitler and Braun were not unique in having to declare it. The Nazis had decreed that all marrying couples must make this pronouncement to ensure the nation’s eugenicist ends.

Given Hitler’s extreme views on eugenics, what would he have done if he had had access to the genetic information that we have today? And what would his DNA tell us if the opportunity ever came to analyze it?

Hitler is one of the most studied men in history. Hundreds of television documentaries continue to pore over the details of his life. But until recently, another “text” has eluded us: his DNA.

In 2021, I was approached by Blink Films, a television production company, with an opportunity to study Hitler’s DNA purportedly from a bloodstained swatch of fabric from the sofa on which Hitler had killed himself. I’m a well-known forensic and ancient DNA specialist and they wanted me to oversee the genetics side of the project. But while the fabric certainly looked as though it could have been cut from the sofa on which Hitler killed himself and the provenance looked good, we needed to be sure.

Ordinarily, this identification would be done by comparing the DNA of a close relative of Hitler with the DNA from the bloodstain. But Hitler left no known living descendants.

There was, however, another route to confirm identification. The Y chromosome is a segment of our DNA inherited through the male line, from father to son. Some years ago, the journalist Jean-Paul Mulders and historian Marc Vermeeren traced distant male-line relatives of Hitler in Europe, obtained a DNA sample from one of them, and analyzed the Y chromosome. This data provided a Y-chromosome DNA profile that could be compared to any Y-chromosome profile generated from the bloodstain on the sofa fabric. It was a match.

The next thing to do was to see what the DNA could, and perhaps more importantly, couldn’t tell us.

Hitler’s health has long been the subject of debate. Without being able to examine him, numerous attempts have been made by medical professionals and historians alike to diagnose conditions Hitler may have suffered from. And there were certainly hints.

While Hitler had been imprisoned in Landsberg Prison in 1923–24, he underwent a medical examination which, according to a relatively recent finding in the records, indicated that he had right-sided cryptorchidism — an undescended testicle.

The results of the sequencing of Hitler’s genome were sent to experts who specialize in sexual-development disorders. Very quickly, they became interested in the fact that Hitler carried a deletion in one of his two copies of a crucial gene for sexual development, PROK2.

This deletion is associated with a condition known as congenital hypogonadotropic hypogonadism (CHH). A rare disorder, it is characterized by an individual’s inability to secret sufficient levels of the hormone GnRH, or if they do, the action is impaired.

As GnRH is vital for stimulating the production of sex hormones, this lack of function can result in the failure or underdevelopment of sexual organs and failed or delayed sexual maturation during puberty. While the resulting visible signs of the condition do vary, microphallus (an unusually small penis, also known as a micropenis) and cryptorchidism (undescended testes) are thus common in male infants with CHH.

This finding caused a bit of a stir during the study. While it’s not possible to tell precisely what Hitler’s genitalia looked like from his DNA, he carried a known disease-causing variant in one of his PROK2 genes that fit with those fragments of historical information about his genitalia.

The irony here, of course, is that Hitler and the Nazis were obsessed with mental and physical “defects” of a hereditary nature.

After the Second World War, the sheer scale and cruelty of Nazi eugenics led to an international revulsion that discredited eugenic ideology and led to its ultimate ethical collapse. But the ideas underlying eugenics, that some people are genetically better than others, have, worryingly, not gone away.

Your genetic make-up is only a small piece in the much larger puzzle that makes you who you are. Just as you are unique genetically, you have your own epigenetic tags, your own life experiences and influences, temporal, societal, and environmental, as well as the choices and decisions you yourself make in life — a specific constellation of factors that make you the person you are. And this, it must be said, is true of everyone, including Adolf Hitler.

Under his own laws, Hitler’s marriage would have been void. Certainly, poetic justice. If Hitler had been shown his own genetics presented under an anonymous name, he almost certainly would have sent himself to the gas chamber.

Turi King is a professor and director of the Centre for Evolution at the University of Bath and the author of “The Secrets of Our DNA: How Genetics Has Changed the World” (out Tuesday).