Human bones from a newborn, a child and four adults or teenagers who lived around 40,000 years ago show clear signs of cutting and of fractures to extract the marrow within, they say.
Just a few years after Charles Darwin first expounded his theory of evolution, Dupont published the results of his own research in his book "Man During the Stone Age".
But his discoveries remained in the archives of the museum (now called the Brussels Institute of Natural Sciences) for more than a century.
In the meantime, here's a definitive timeline of the couple's royal relationship.
Harry and Markle first made each other's acquaintance on a blind date in early July, 2016.
The bones in Goyet date from when Neanderthals were nearing the end of their time on earth before being replaced by Homo sapiens, with whom they also interbred.
Once regarded as primitive cavemen driven to extinction by smarter modern humans, studies have found that Neanderthals were actually sophisticated beings who took care of the bodies of the deceased and held burial rituals.
But there is a growing body of proof that they also ate their dead.
Neanderthal bone fragments Cases of Neanderthal cannibalism have been found until now only in Neanderthal populations in southern Europe in Spain, at El Sidron and Zafarraya, and in France, at Moula-Guercy and Les Pradelles.
"We were introduced actually by a mutual friend," Harry revealed during the couple's first sit-down interview with the BBC following their engagement announcement. News recently claimed Harry's friend Violet von Westenholz is the one who introduced them, but others have speculated it was fashion designer Mischa Nonoo.) Despite Prince Harry's global fame, Markle says she didn't have a lot of preconceived notions about who he was before they met.
"Because I’m from the States, you don’t grow up with the same understanding of the royal family," she explained during the BBC interview.
That was until 2004, when the institute's head of anthropology Patrick Semal discovered, hidden in amongst the drawers of what Dupont thought were human bones, a jaw tip that clearly belonged to a Neanderthal.