Animals with human DNA
It was one of the great comedy sketch moments from Not the Nine O'Clock News. Mel Smith is a scientist on a talk-show, sitting next to a gorilla (Rowan Atkinson in a costume) and begins explaining how he has taught him to speak.
Smith: "When I caught Gerald in '68 he was completely wild."
Gerald/Atkinson: "Wild. I was absolutely livid."
Funny, yes, and truly far-fetched, but experiments on animals that lead to possible human characteristics are something the Academy of Medical Sciences has spent nearly two years considering.
It looked at the vast and growing area of research involving the insertion of human DNA or cells into animals.
This sort of research has been going on for decades. It can involve a single gene being inserted in a mouse genome, or the transplantation of human cells or tissue into animals, creating what are known as chimaeras.
The point is to study human development and disease - anything from cancer, stroke or dementia to Down's syndrome.
People know that experimentation on animals takes place, but probably very few know much about this area. The academy commissioned a consortium led by the polling organisation Ipsos Mori to look at public opinion.
The public consultation showed strong support as long as people felt it would produce genuine benefits for medicine and that these would be widely available.
Most of this area of research involves mice, but rats, fruit flies and zebra fish are also used.
One of the key areas of potential concern outlined in the report is research involving the brain: "The predominant question is whether populating an animal's brain with human-derived cells could result in the production of an animal with human cognitive capacity" - areas such as consciousness, awareness and sentience and human-like behavioural capabilities.
The academy thinks if human brain stem cells were transplanted into a mouse in the womb, it would still probably end up acting like a mouse. But it is less certain about the potential consequences for a similar experiment with a larger animal, for example a sheep or pig.
Professor Martin Bobrow, who chaired the working group which compiled the report, suggested what he called the "Great Ape test". He said there is a consensus that experiments should not be carried out on Great Apes (chimpanzees, orangutans and gorillas). So if experiments to add human material gave a sheep or a pig the same level of cognitive ability as a gorilla, then it should probably not be allowed.
The academy is not suggesting that anyone wants to do this, but it says public discussion should occur now, long before scientists have the idea for unusual experiments.
So what else might make you feel uncomfortable? Animals with human physical features would be a step too far for many - bringing to mind HG Wells science fiction novel The Island of Dr Moreau.
And what about language? The report says: "Creating characteristics such as speech and behaviour in animals would be very complex." Considerable potential benefits would need to be justified before that was allowed.
After all, as one of the report authors said: "If you come home and your parrot says - 'who's a pretty boy?' - that's one thing. If you come home and your monkey says it, that's quite another."