A renowned scientist has made a sensational claim that almost 100 years ago, a human-chimp hybrid was created in a lab in the US - before later being killed by panicked doctors.
Evolutionary psychologist Gordon Gallup claims his former university professor confirmed that a successful 'humanzee' experiment occurred in Orange Park, Florida in the 1920s.
It would mean that a female chimp was artificially inseminated with human sperm, before successfully falling pregnant with a half-human, half ape child.
Gallup told The Sun: "They inseminated a female chimpanzee with human semen from an undisclosed donor and claimed not only that pregnancy occurred, but the pregnancy went full term and resulted in a live birth.
"But in a matter of days, or a few weeks, they began to consider the moral and ethical considerations and the infant was euthanised."
Gallup is adamant that the man who told him about the experiment is a credible scientist, who worked at Yerkes before the research centre was relocated to Emory University in Atlanta, Georgia, in 1930.
The earliest and most notable example of human-ape hybridisation is the work of Russian scientist Ilya Ivanovich Ivanov, who conducted a series of famous experiments in the 1920s.
He inseminated female chimpanzees with human sperm, but none of the animals ever fell pregnant.
Ivanov also set up several controversial experiments involving ape sperm and human volunteers, but his project was halted and never resumed.
More recently, in 1958, Oliver the chimpanzee was touted as a humanzee, due to his unusually human-like appearance.
He was able to walk upright, instead of on his knuckles, and was bald with freckles and a protruding nose, which only added to the speculation.
But in 1996, a DNA test revealed that Oliver had 48 chromosomes - the number of a normal chimpanzee.
It was claimed that he he 47 - the number in between a chimp's 48 and a human's 46 chromosomes.
Oliver died in 2012, at the age of 55.
Gallup claims that it's not only possible to crossbreed humans with chimpanzees, but with all the great apes, including gorillas and orangutan.
He added: "Humans and all three of the great apes species are all descended from a single common ape-like ancestry.
“I’ve also coined what would be the appropriate terms to refer to human-gorilla hybrids and human-orangutan hybrids which would be a ‘hurilla’ and a 'hurang'."
But while he admits it would be "fascinating" to see a real-life example of a humanzee, Gallup is unsure whether the costs of such a bizarre and controversial biological experiment would outweigh the benefits.