Scientists injected human brain cells into mouse foetuses, creating a strain of mice that were approximately 1% human. A team headed by a distinguished molecular biologist, Irving Weissman, at Stanford University is considering a follow-up that would produce mice whose brains are 100% human. Weissman says that he would keep a tight rein on the mice, and if they showed any signs of humanness he would kill them. Hardly reassuring.
The first chimeric experiment occurred many years ago when scientists in Edinburgh fused a sheep and goat embryo - two unrelated animal species that are incapable of mating and producing a hybrid offspring. The resulting creature, called a geep, was born with the head of a goat and the body of a sheep.
What if human stem cells - the primordial cells that turn into the body's 200 or so cell types - were to be injected into an animal embryo and spread throughout the animal's body into every organ? Some human cells could migrate to the testes and ovaries where they could grow into human sperm and eggs. If two of the chimeric mice were to mate, they could potentially conceive a human embryo. If the human embryo were to be removed and implanted in a human womb, the resulting human baby's biological parents would have been mice.
Are we on the cusp of a biological renaissance, or sowing the seeds of our destruction?
Firstly, how come I never saw a picture of the geep? All that stuff with ears on the back of mice, and they had a sheep with the head of a goat! Secondly, how will this guy tell if the mice are showing signs of humanness? If they have 100% human brain won't they automatically be showing human behaviour?
The popular but underrated cartoon Pinky and the Brain may well have been based on this guy's research...
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