Raising Beast People; Science Is Blurring the Line between Humans and Animals
Silver, Lee M., Newsweek International
Byline: Lee M. Silver (Silver is a professor at Princeton's Department of Molecular Biology and the Woodrow Wilson School of Public and International Affairs. He is also the author of "Challenging Nature: The Clash of Science and Spirituality at the New Frontiers of Life." He has no financial interests in or consulting arrangements with any biotechnology or pharmaceutical company.)
High up on the bluffs overlooking the Pacific Ocean in southern California, strange animals scurry about in their cages. They eat, drink, copulate and occasionally try to run away from human hands that enter their confined quarters. If you didn't know better, you would think they were ordinary mice. But these particular animals contain a hidden component not present in their naturally conceived cousins. Inside their brains are living human neurons that help them to see, hear and think.
Fred Gage, a biologist at the Salk Institute, has created these part-human animals to understand how human neurons degrade or die in people suffering from neurodegenerative diseases such as Parkinson's and Alzheimer's. Studying and perturbing brain cells in their natural environment--which is to say, inside a functioning brain--provide the best hope for developing therapies to prevent or overcome disease symptoms. But experimentation on human brains is obviously unacceptable, and so scientists are hoping that animals with a small percentage of human brain cells will provide a substitute for human subjects.
Many people, however, are deeply disturbed by this research. U.S. President George W. Bush believes that scientists like Gage have stepped across a moral line that must be defended, even at the cost of biomedical progress. In his 2006 State of the Union address, he implored Congress to "pass legislation to prohibit the most egregious abuses of medical research [including] creating human-animal hybrids," because "human life is a gift from our Creator" that should never be "devalued." Bush has already set back progress on research on stem cells, which are harvested from days-old embryos, by putting restrictions on their use. Now he and other leaders may be girding to attack the next promising area of biological research.
Scientists call these part-human animals chimeras, after the creature in Greek mythology with the head of a lion, the torso of a goat and a tail sprouting the head of a venomous snake. The Greeks considered the chimera a monster because it violated a perceived "natural order" in which each species is a separate and unique category. So profound was this violation thought to be that thinkers over the millenniums have assumed such creatures could not possibly exist in reality. This conventional wisdom was shattered in March 1984, when an animal unlike any other ever born, or seen, adorned the cover of Nature, the international journal of science. Danish embryologist Steen Willadsen had mixed cells from the embryos of a sheep and a goat in a petri dish and created a "geep"--a mosaic animal with the head of a goat and the woolly upper torso of a sheep. The geep wasn't much more than a biological curiosity. In the past few years, however, explosive advances in stem-cell biology have provided scientists with the ability to create human-animal chimeras--a development that could potentially revolutionize biomedical analysis and therapy.
This progress raises a simple question: how far should scientists be allowed to go down the chimera path? Unfortunately, there is no simple answer. On one side are the potential benefits to biomedical research and human health. On the other, there's our deep-seated abhorrence to the idea of combining humans and animals--and the weird possibility that the animals we create for purposes of experimentation could wind up falling under our definition of persons, with all the rights that follow.
Efforts to create human replacement organs are probably the least controversial use of chimeras. …