Scientists, who are being called “Frankenstein scientists” are knowingly developing part human part animal chimeras. They want to implant human stem cells in an animal embryo to grow “specific” human organs. What could go wrong?
These bold and controversial plans are the culmination of more than three decades of research. These experiments have helped us understand some of the biggest mysteries of life, delineate the boundaries between species, and explore how a ragbag bunch of cells in the womb coalesce and grow into a living, breathing being.
With new plans to fund the projects, we are now reaching a critical point in this research. “Things are moving very fast in this field today,” says Janet Rossant at the Hospital for Sick Children in Toronto, and one of the early pioneers of chimera research. “It's going to open up a new understanding of biology.”
That is, provided we can resolve some knotty ethical issues first – questions that may permanently change our understanding of what it means to be human.
For millennia, chimeras were literally the stuff of legend. The term comes from Greek mythology, with Homer describing a strange hybrid “of immortal make, not human, lion-fronted and snake behind, a goat in the middle”. It was said to breathe fire as it roamed Lycia in Asia Minor.
In reality, chimeras in science are less impressive. The word describes any creature containing a fusion of genetically-distinct tissues. This can occur naturally, if twin embryos fuse soon after conception, with striking results.
Consider the “bilateral gynandromorphs“, in which one side of the body is male, the other female. These animals are essentially two non-identical twins joined down the centre. If the two sexes have wildly different markings – as is the case for many birds and insects – this can lead to a bizarre appearance, such as a northern cardinal that had grown bright red plumage on half of its body, while the rest was grey.
Most often, however, the cells mix to form a subtler mosaic across the whole body, and chimeras look and act like other individuals within the species. There is even a chance that you are one yourself. Studies suggest that at least 8% of non-identical twins have absorbed cells from their brother or sister.
The mixed bag of animals from Greek legends certainly cannot be found in nature. But this has not stopped scientists from trying to create their own hybrid chimeras in the lab.
Janet Rossant, then at Brock University, Canada, was one of the first to succeed. In 1980, she published a paper in the journal Science announcing a chimera that combined two mice species: an albino laboratory mouse (Mus musculus) and a Ryukyu mouse (Mus caroli), a wild species from east Asia.
Previous attempts to produce a hybrid “interspecific” chimera often ended in disappointment. The embryos simply failed to embed in the uterus, and those that did were deformed and stunted, and typically miscarried before they reached term.
As it turns out, scientists have been trying this for several years. This could be a great scientific breakthrough or it could be a cruel act of man. Just because you have the ability to play God, does it give you the right to? I think that's the question people should be asking.