[Paleopsych] Natl Geog: Animal-Human Hybrids Spark Controversy

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Animal-Human Hybrids Spark Controversy
Maryann Mott
January 25, 2005

[I'm taking my annual Lenten break from forwarding articles again this 
year. It's a vice to spend so much time doing this. So I'll be off the air 
for forty days and forty nights from Ash Wednesday until Easter.]

    Scientists have begun blurring the line between human and animal by
    producing chimeras--a hybrid creature that's part human, part animal.

    Chinese scientists at the Shanghai Second Medical University in 2003
    successfully fused human cells with rabbit eggs. The embryos were
    reportedly the first human-animal chimeras successfully created. They
    were allowed to develop for several days in a laboratory dish before
    the scientists destroyed the embryos to harvest their stem cells.

    In Minnesota last year researchers at the Mayo Clinic created pigs
    with human blood flowing through their bodies.

    And at Stanford University in California an experiment might be done
    later this year to create mice with human brains.

    Scientists feel that, the more humanlike the animal, the better
    research model it makes for testing drugs or possibly growing "spare
    parts," such as livers, to transplant into humans.

    Watching how human cells mature and interact in a living creature may
    also lead to the discoveries of new medical treatments.

    But creating human-animal chimeras--named after a monster in Greek
    mythology that had a lion's head, goat's body, and serpent's tail--has
    raised troubling questions: What new subhuman combination should be
    produced and for what purpose? At what point would it be considered
    human? And what rights, if any, should it have?

    There are currently no U.S. federal laws that address these issues.

    Ethical Guidelines

    The National Academy of Sciences, which advises the U.S. government,
    has been studying the issue. In March it plans to present voluntary
    ethical guidelines for researchers.

    A chimera is a mixture of two or more species in one body. Not all are
    considered troubling, though.

    For example, faulty human heart valves are routinely replaced with
    ones taken from cows and pigs. The surgery--which makes the recipient
    a human-animal chimera--is widely accepted. And for years scientists
    have added human genes to bacteria and farm animals.

    What's caused the uproar is the mixing of human stem cells with
    embryonic animals to create new species.

    Biotechnology activist Jeremy Rifkin is opposed to crossing species
    boundaries, because he believes animals have the right to exist
    without being tampered with or crossed with another species.

    He concedes that these studies would lead to some medical
    breakthroughs. Still, they should not be done.

    "There are other ways to advance medicine and human health besides
    going out into the strange, brave new world of chimeric animals,"
    Rifkin said, adding that sophisticated computer models can substitute
    for experimentation on live animals.

    "One doesn't have to be religious or into animal rights to think this
    doesn't make sense," he continued. "It's the scientists who want to do
    this. They've now gone over the edge into the pathological domain."

    David Magnus, director of the Stanford Center for Biomedical Ethics at
    Stanford University, believes the real worry is whether or not
    chimeras will be put to uses that are problematic, risky, or

    Human Born to Mice Parents?

    For example, an experiment that would raise concerns, he said, is
    genetically engineering mice to produce human sperm and eggs, then
    doing in vitro fertilization to produce a child whose parents are a
    pair of mice.

    "Most people would find that problematic," Magnus said, "but those
    uses are bizarre and not, to the best of my knowledge, anything that
    anybody is remotely contemplating. Most uses of chimeras are actually
    much more relevant to practical concerns."

    Last year Canada passed the Assisted Human Reproduction Act, which
    bans chimeras. Specifically, it prohibits transferring a nonhuman cell
    into a human embryo and putting human cells into a nonhuman embryo.

    Cynthia Cohen is a member of Canada's Stem Cell Oversight Committee,
    which oversees research protocols to ensure they are in accordance
    with the new guidelines.

    She believes a ban should also be put into place in the U.S.

    Creating chimeras, she said, by mixing human and animal gametes
    (sperms and eggs) or transferring reproductive cells, diminishes human

    "It would deny that there is something distinctive and valuable about
    human beings that ought to be honored and protected," said Cohen, who
    is also the senior research fellow at Georgetown University's Kennedy
    Institute of Ethics in Washington, D.C.

    But, she noted, the wording on such a ban needs to be developed
    carefully. It shouldn't outlaw ethical and legitimate
    experiments--such as transferring a limited number of adult human stem
    cells into animal embryos in order to learn how they proliferate and
    grow during the prenatal period.

    Irv Weissman, director of Stanford University's Institute of
    Cancer/Stem Cell Biology and Medicine in California, is against a ban
    in the United States.

    "Anybody who puts their own moral guidance in the way of this
    biomedical science, where they want to impose their will--not just be
    part of an argument--if that leads to a ban or moratorium. ... they
    are stopping research that would save human lives," he said.

    Mice With Human Brains

    Weissman has already created mice with brains that are about one
    percent human.

    Later this year he may conduct another experiment where the mice have
    100 percent human brains. This would be done, he said, by injecting
    human neurons into the brains of embryonic mice.

    Before being born, the mice would be killed and dissected to see if
    the architecture of a human brain had formed. If it did, he'd look for
    traces of human cognitive behavior.

    Weissman said he's not a mad scientist trying to create a human in an
    animal body. He hopes the experiment leads to a better understanding
    of how the brain works, which would be useful in treating diseases
    like Alzheimer's or Parkinson's disease.

    The test has not yet begun. Weissman is waiting to read the National
    Academy's report, due out in March.

    William Cheshire, associate professor of neurology at the Mayo
    Clinic's Jacksonville, Florida, branch, feels that combining human and
    animal neurons is problematic.

    "This is unexplored biologic territory," he said. "Whatever moral
    threshold of human neural development we might choose to set as the
    limit for such an experiment, there would be a considerable risk of
    exceeding that limit before it could be recognized."

    Cheshire supports research that combines human and animal cells to
    study cellular function. As an undergraduate he participated in
    research that fused human and mouse cells.

    But where he draws the ethical line is on research that would destroy
    a human embryo to obtain cells, or research that would create an
    organism that is partly human and partly animal.

    "We must be cautious not to violate the integrity of humanity or of
    animal life over which we have a stewardship responsibility," said
    Cheshire, a member of Christian Medical and Dental Associations.
    "Research projects that create human-animal chimeras risk disturbing
    fragile ecosystems, endanger health, and affront species integrity."

    Photograph: Chimera
    An ancient Etruscan statue of a chimera found in north-central Italy.
    The mythic beast had a lion's body, serpent's tail, and goat's head.
    Photograph by James P. Blair, copyright National Geographic Society

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