Last month, Unknown Country reported the views of technology heavyweights such as Elon Musk that artificial intelligence could be the most significant threat to the future of mankind. Now Stephen Hawking has added his voice to their ever-increasing concerns regarding the outcome of creating intelligent machines.

“The primitive forms of artificial intelligence we already have proved very useful, " said Hawking. but the I think the development of true artificial intelligence could spell the end of the human race.”

“Humans limited by slow biological evolution cannot compete and will be superseded.”

Hawking maintains that “once humans develop artificial intelligence, it will take off on its own and redesign itself at an ever-increasing rate.”

With such dire warnings regarding the dangers of artificial intelligence being echoed around the world by eminent experts, it seems that science has branched out in a new, but equally disturbing direction.

Researchers at the University of Rochester Medical Centre in New York have now begun to inject mice with human brain cells with the result that they become much more intelligent than their fellow rodents. The injected cells, known as glial cells, began to grow and multiply, replacing the counterpart cells in the host brains and causing them to become more human-like.

The researchers wrote: "After a few months we start to see the glial progenator cells being replaced by the human cells.

"The mouse glial progenator cells either die off or flee to the outer regions of the brain.

"After a year almost all of the glial progenator cells have been replaced with human cells and so have most of the astrocytes. These have a natural regular turn over in the brain and are replaced by glial progenator cells that mature. So the human cells out compete and replace the mouse cells.

"This ultimately generates mice with humanised brain that supports the neurons."

The human cells, which were extracted from aborted foetuses, appeared to enhance the brains of the human-hybrid mice, who displayed improved cognitive function such as better memory recall.

"So we are not creating a human brain in the mice, but it seems to improve the efficiency of the mouse neural network that is already there. They do not get any additional capabilities that could be seen as human," commented the researchers.

"It can be suggested that we could try this technique in monkeys and apes but we are not trying to make animals more intelligent."

The project, which was led by Dr Steven Goldman and was published in the Journal of Neuroscience, is ostensibly being carried out to further studies for neurological conditions such as schizophrenia, but there are concerns that enhancing the intelligence of animals in this way could be very risky.

If the cells continue to multiply inside the host brains, do the animals become increasingly more intelligent? Could we be unwittingly creating a "Frankenstein’s monster?" Could the hybrid animals potentially become more intelligent than their creators?

While other academics were enthusiastic about the results of the amazing research, they were more guarded in their enthusiasm for its long-term potential and warned against putting cells into other types of animals.

Professor Wolfgang Endard, from Ludwig-Maximilians University Munich in Germany, said: ‘If you make animals more human-like, where do you stop?’