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Apr 08, 2006 09:01 PM
by Cass Silva

 Chimeras (ki-MER-ahs) -- meaning mixtures of two or  more individuals in a=
 single body -- are not inherently unnatural. Most twins  carry at least a =
few cells from the sibling with whom they shared a womb, and  most mothers =
carry in their blood at least a few cells from each child they have  born.=
 Recipients of organ transplants are also chimeras,  as are the many people=
 whose defective heart valves have been replaced with  those from pigs or c=
ows. And scientists for years have added human genes to  bacteria and even =
to farm animals -- feats of genetic engineering that allow  those critters =
to make human proteins such as insulin for use as medicines.=20=20
 "Chimeras are not as strange and alien as at first  blush they seem," said=
 Henry Greely, a law professor and ethicist at Stanford  University who has=
 reviewed proposals to create human-mouse chimeras there.=20=20
 But chimerism becomes a more sensitive topic when it  involves growing ent=
ire human organs inside animals. And it becomes especially  sensitive when =
it deals in brain cells, the building blocks of the organ  credited with ma=
king humans human.=20
 In experiments like those, Greely told the academy  last month, "there is =
a nontrivial risk of conferring some significant aspects  of humanity" on t=
he animal.=20
 Greely and his colleagues did not conclude that such  experiments should n=
ever be done. Indeed, he and many other philosophers have  been wrestling w=
ith the question of why so many people believe it is wrong to  breach the s=
pecies barrier.=20
 Does the repugnance reflect an understanding of an  important natural law?=
 Or is it just another cultural bias, like the once  widespread rejection o=
f interracial marriage?=20
 Many turn to the Bible's repeated invocation that  animals should multiply=
 "after their kind" as evidence that such experiments are  wrong. Others, h=
owever, have concluded that the core problem is not necessarily  the creati=
on of chimeras but rather the way they are likely to be treated.=20=20
 Imagine, said Robert Streiffer, a professor of  philosophy and bioethics a=
t the University of Wisconsin, a human-chimpanzee  chimera endowed with spe=
ech and an enhanced potential to learn -- what some have  called a "humanze=
 "There's a knee-jerk reaction that enhancing the  moral status of an anima=
l is bad," Streiffer said. "But if you did it, and you  gave it the protect=
ions it deserves, how could the animal complain?"=20
 Unfortunately, said Harvard political philosopher  Michael J. Sandel, spea=
king last fall at a meeting of the President's Council on  Bioethics, such =
protections are unlikely.=20
 "Chances are we would make them perform menial jobs  or dangerous jobs," S=
andel said. "That would be an objection."=20
A Research Breakthrough=20

 The potential power of chimeras as research tools  became clear about a de=
cade ago in a series of dramatic experiments by Evan  Balaban, now at McGil=
l University in Montreal. Balaban took small sections of  brain from develo=
ping quails and transplanted them into the developing brains of  chickens.=
 The resulting chickens exhibited vocal trills and  head bobs unique to qua=

How low will we go? Check out Yahoo! Messenger=92s low  PC-to-Phone call ra=

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