Scientists come one step closer to growing human organs in genetically modified animals by successfully creating a human-pig hybrid.

In this recent breakthrough, scientists have managed to grow embryos that are 0.001% human and the rest pig.

Scientist achieved this creation by injecting a pig embryo with human stem cells, then implanting the embryo back into the sow for one month.

The new embryos have been titled ‘chimeras’, after the lion-goat-serpent monster of Greek mythology, and have been described as ‘exciting’ by fellow researchers.

Although inefficient, with most embryos failing to develop to the 28 day stage, this is a revolutionary step.

Professor Juan Carlos Izpisua Belmonte


The reason for the inefficiency was explained by Professor Juan Carlos Izpisua Belmonte of the Salk Institute: ‘Humans and pigs are separated by a long time in evolution’.

The key failing is the disparity in gestation periods between pigs and humans.

Professor Belmonte provides an analogy: ‘it is like a freeway with one car going much faster than another – you’re more likely to have an accident’.

In the long term, cows will host human organs as both cows and human pregnancies last nine months.

Progress had already been documented on the subject of growing organs in one species to be used in another.

Studies saw rats genetically modified in order not to grow a pancreas – the organ responsible for controlling blood sugar levels.

Mouse stem cells were injected into the modified rat embryos and in the absence of a rat pancreas, a mouse pancreas grew.

Despite the research being legal, scientists are aware of the controversy surrounding these experiments.

Professor Belmonte understands concerns: ‘One possibility is to let these animals be born, but that is not something we should allow to happen at this point.

‘Not everything that science can do we should do, we are not living in a niche in lab, we live with other people - and society needs to decide what can be done.’