Creating Chimeras--Stuart A. Newman on interspecies human-animal hybrids ethics biotech science moral experiment

A cell biologist talks about the reality of part-human, part-animal creatures, and why his 'humanzee' patent was rejected.

BY: Interview with Dr. Stuart A. Newman

Reprinted from the May 2005 issue of Science & Theology News. Used with permission.

Eight years ago, Dr. Stuart A. Newman, a professor of cell biology and anatomy at New York Medical College, applied for a patent on a humanzee, a hypothetical creature that would be half-human and half-chimpanzee. After much delay, his application was rejected by the U.S. Patent and Trademark Office. In truth, Newman now says, he was only trying to make the point that we have not thought long enough - or well enough - about the biotech future that quickly is becoming our present reality.

Science & Theology News' web editor Matt Donnelly asked Newman about chimeras, humanzees and whether religious people should be concerned about a proliferation of human-animal mixtures.

What is a chimera?

To biologists, a chimera is an animal that is part one kind, part another, at the cell or tissue level. This distinguishes it from a hybrid, which is a blend of two species in every cell of its body. An example of a hybrid is a mule, which is the offspring of a male donkey and female horse. Since a mule results from a fertilization event, each of its cells contains equal amounts of horse and donkey DNA.

How can one create a chimera?

A chimera can result from one of several types of procedures other than fertilization:

Grafting tissues from one species into another at a mature stage of development. Such "xenografting," which would include transfer of pig brain or heart tissue into Parkinson's or cardiac patients, does not alter the species identity of the host, but incurs the risk of passing new viruses to the recipient, or even causing new viruses to be created.

Grafting tissues from one species of animal into the late-stage embryo of another. While this technique can lead to extensive replacement of a specific tissue system of the recipient (it has been used, for example, to produce mice with a human immune system for AIDS research), like (i) it does not alter the species type of the host (although mice with brains consisting entirely of human cells could be produced by this method).

Mixing cells from two or more embryos (or embryonic stem cells) of different species at early stages of development and allowing the chimeric embryos to develop to later stages, or to full term. Unlike (i) and (ii), this "embryo chimera" technique can produce an animal of uncertain species identity, since every organ can potentially have any proportion of cells of the different species types. "Geeps" were first produced in this fashion in the 1980s from goat and sheep embryos.

Most people - other than committed animal rights advocates - will accept the chimeras of (i), and (ii) if the recipient embryo is not human. Many people are disquieted by the embryo chimeras of (iii), even if applied only to nonhuman animals. Most people would have a problem with (iii) if human embryo cells are part of the mixture.

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The Peril and Promise of Mix-and-Match Biotech

A cell biologist talks about the reality of part-human, part-animal creatures, and why his 'humanzee' patent was rejected.

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