A famed Polish general who fought in the American Revolutionary war and became a protege of George Washington may have been intersex, researchers say.

Scientists first found that Casimir Pulaski's skeleton had female characteristics about 20 years ago, but were unable to prove it was definitely him.

But DNA testing has now confirmed the female skeleton contained in a metal box under the monument to the general in Georgia was indeed Mr Pulaski's.

The new evidence suggests that although Mr Pulaski identified and lived as a man, biologically, he did not fit into the binary definitions of male and female, a twist that helps explain why scientists could not previously identify his remains.

Their findings will be set out in a Smithsonian Channel documentary, called "America's Hidden Stories: The General Was Female?" on 8 April.

Richard III – the final act: Archaeologists release image of skull that might be that of a king Show all 2 1 /2 Richard III – the final act: Archaeologists release image of skull that might be that of a king Richard III – the final act: Archaeologists release image of skull that might be that of a king Richard-pa.jpg PA Richard III – the final act: Archaeologists release image of skull that might be that of a king king-richard2-reu.jpg Reuters

The discovery offers historical representation to people who are intersex, a group that has often been stigmatised and overlooked throughout history.

About one in 2,000 people is born with ambiguous genitalia, which can lead doctors to perform what advocates say are unnecessary and harmful surgeries, according to the Intersex Society of North America.

But intersex includes a variety of conditions, and many more people have subtler variations in sex anatomy, which may manifest later in life – or not at all.

Some estimates suggest that about 1.7 per cent of the population has intersex traits, making such characteristics about as common as having red hair.

Although Mr Pulaski’s role in history has long been embraced in areas with strong Polish and Catholic ties – his birthday is an Illinois state holiday and he is celebrated with an annual Polish pride parade in New York City – the new findings now also place him alongside the few historical figures who are known to have had intersex traits.

Kimberly Zieselman, executive director of interACT, an advocacy organisation for children with intersex traits, said Mr Pulaski’s life showed what can happen when intersex people are allowed to live as they were born, without early surgical intervention.

“What’s happening today is so wrong,” Ms Zieselman said. “You are erasing people like this person who went on, untouched, to be a war hero.”

“This is what can happen if kids are left alone – natural and healthy as they are,” she added.

Born in Poland in 1745, Mr Pulaski fought for his home country against the Russians before fleeing to France, where he met Benjamin Franklin.

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He came to the United States in 1777 to serve in Washington’s army and helped form the American calvary, which played a crucial role during the Revolutionary War. Some even credit Mr Pulaski with saving Washington’s life during the Battle of Brandywine.

In 1779, Mr Pulaski was mortally wounded in battle in Savannah. Some said he had been buried at a local plantation, and later, those remains were moved to a monument honouring him in a downtown square.

The remains were exhumed for testing in the 1990s, but an investigation was inconclusive.

The skeleton was about the right height and age for Mr Pulaski, who was most likely about 5ft 1in to 5ft 4in and died when he was 34.

It also showed injuries consistent with Mr Pulaski’s life, said Virginia Hutton Estabrook, an assistant professor of anthropology at Georgia Southern University who worked on the case.

But there was a big catch: “The skeleton looked very female,” she said.

The pelvic bones, a primary way of distinguishing sex in skeletons, indicated that the person had probably been a woman, and the body had other female characteristics, including a delicate face and rounded jaw line, Ms Estabrook said.

“To our great frustration, we were unable to solve the mystery,” Chuck Powell, a historian who was on the original investigation team, told the Associated Press in 2005, adding that some thought “we ought to stop here and declare it a female and walk away.”

But the mystery nagged at researchers, including Ms Estabrook and Mr Powell’s daughter, Lisa Powell, who more recently investigated the case with new technology.

A DNA test led to a breakthrough: The remains were a match with a relative of Mr Pulaski who died in the 1800s and whose own remains were exhumed for testing from a grave in Poland.

That raised a whole new question: How could researchers square the skeletal evidence with the documented evidence from Mr Pulaski’s life, which showed that he was baptised as a son, fought in battle as a man and displayed certain masculine traits, such as facial hair and male-pattern baldness?

Researchers concluded he must have had intersex traits. “That is the only way that these two things make sense together,” Ms Estabrook said.

That discovery does not change Mr Pulaski’s identity – “he was always a ‘he’ as far as his gender,” she said – but it does open up the possibility for further research into a hidden part of history.

According to Ms Estabrook, there have been other cases in which skeletons that appeared to be one sex were found with objects associated with the opposite sex.

In 2017, scholars announced that a famous Viking tomb in Sweden contained the remains of a woman, which in that case seemed to provide support for the theory that there were female Viking warriors.

“There are quite a few cases like this, and our go-to interpretation has not been intersex,” Ms Estabrook said.

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In Mr Pulaski’s case, Ms Zieselman said the discovery highlighted the intersex community’s fight against invisibility – first, by history, when it was common for people not to know they were intersex, and more recently, by surgeries that she said erase intersex traits and identity.

“Just imagine if Casimir Pulaski were born today,” Ms Zieselman said. He may have been raised as a girl, she said, making it unlikely that he would have joined the military and helped Washington.

“Arguably, if urologists had tried to ‘fix’ Pulaski’s body, the US could still be a British colony.”