The Yuck Factor

Imagine an ape that laughs like Phyllis Diller. Imagine a sheep with human arms growing from its body, a fantasy – for now -- on the edge of stem cell research.

Such creatures are called chimeras, a word derived from the monstrous beast of Greek mythology -- part lion, part serpent and part goat.

Author Jamie Shreeve wrote about the 2005 versions of chimeras in the New York Sunday Times Magazine. Some of his examples are located here in the west, such as experiments involving implantation of human stem cells in sheep.

Esmail Zanjani, a hematologist in the College of Agriculture, Biotechnology and Natural Resources at the University of Nevada at Reno, says he has sheep with livers that are 40 percent humanized. Shreeve, in discussing the ethics of such situations, asks the rhetorical question, “What if, instead of internal human organs, Zanjani's sheep sported recognizably human parts on the outside -- human limbs or genitals, for instance, ready for transplant should the need arise?”

Shreeve's article also discusses experiments by Irving Weissman in California. “Several years ago, Weissman and his colleagues at Stanford and at StemCells Inc., a private company he helped to found, transplanted human neural stem cells into the brains of newborn mice.” Weissman is now considering the possibility of making a mouse brain composed entirely of human neurons.

Taking it a step further, Shreeve wrote about possibilities involving primates. '''One could imagine that if you took a human embryonic midbrain and spliced it into a developing chimpanzee, you could get a chimp with many of our automatic vocalizations,''' says Terrence Deacon, a biological anthropologist at the University of California at Berkeley and a member of the Johns Hopkins committee. 'It wouldn't be able to talk. But it might laugh or sob, instead of pant-hoot.'''

Which brings us to the possibility of an ape that laughs like Phyllis Diller” and what some in the stem cell field call “the yuck factor.”

Recommended reading, especially for those of us less versed in the science of stem cells.