The process would not be legal in many countries and would involve using DNA extracted from fossils.

George Church, a genetics professor of Harvard School of Medicine, said that the process was possible and that far from being brutal and primitive, Neanderthals were intelligent beings.

They are believed to be one of the ancestors of modern man and became extinct 33,000 years ago. He added that altering the human genome could also provide the answers to curing diseases such as cancer and HIV, and hold the key to living to 120.