Scientists are going too far in creating mixed human-animal organisms, a Scottish organization is warning. The Scottish Council on Human Bioethics, a professional group based in Edinburgh, has published a report on the ethical implications of the practice in the journal Human Reproduction and Genetic Ethics. The report is online at www.schb.org.uk.

“Crossing the human species barrier is a procedure that has always fascinated humanity,” noted the report, made public Tuesday and written in light of draft legislation on human embryology being prepared by the U.K. Department of Health, to be published this summer.

Ancient Greek mythology speaks of monsters such as the Minotaur—a man with a bull’s head—and centaurs, mixtures of humans and horses.

But creatures of this nature may not remain confined to mythology for long, as scientists have begun tentatively creating mixed organisms. An array of experiments have produced animals with some human cells, for instance.

Such procedures “mix human and animal biological elements to such an extent that it questions the very concept of being entirely human,” the report said. This raises “grave and complex ethical difficulties.”

Some ethicists worry that the experiments might force society to make confounding decisions on whether, say, a human-chimp mix would have human rights. Other concerns are that such a creature could suffer from being outcast as a “monster,” from having a chimp as its biological father or mother, or from unusual health problems.

Some inter-species mixtures are powerful research tools, the report said.

This “became clear about a decade ago in a series of dramatic experiments in which small sections of brains from developing quails were taken and transplanted into the developing brains of chickens. The resulting chickens exhibited vocal trills and head bobs unique to quails, proving that the transplanted parts of the brain contained the neural circuitry for quail calls. It also offered astonishing proof that complex behaviours could be transferred across species.”

Later research has spawned human-animal creations, the report said. These usually die at the embryonic stage, but often survive if the mixtures involve only a few cells or genes transferred from one species to another.

The council cited the following examples:

• In 2003, scientists at Cambridge University, U.K. conducted experiments involving fusing the nucleus of a human cell into frog eggs. The stated aim was to produce rejuvenated “master cells” that could be grown into replacement tissues for treating disease. It was not clear whether fertilization took place, but “some kind of development was initiated,” the report said.
• In 2005, U.K. scientists transplanted a human chromosome into mouse embryos. The newly born mice carried copies of the chromosome and were able to pass it on to their own young.
• The company Advanced Cell Technologies was reported, in 1999, to have created the first human embryo clone by inserting a human cell nucleus into a cow’s egg stripped of chromosomes. The result was an embryo that developed and divided for 12 days before being destroyed.
• Panayiotis Zavos, the operator of a U.S. fertility laboratory, reported in 2003 that he had created around 200 cow-human hybrid embryos that lived for about two weeks and grew to several hundred cells in size, beyond the stage at which cells showed the first signs of developing into tissues and organs.
• In 2003, Hui Zhen Sheng of Shanghai Second Medical University, China, announced that rabbit-human embryos had been created by fusing human cells with rabbit eggs stripped of their chromosomes. The embryos developed to the approximately 100-cell stage that forms after about four days of development.

The council made 16 recommendations, including that it should be illegal to mix animal and human sperm and eggs, or to create an embryo containing cells consisting of both human and animal chromosomes.

“The fertilisation of animal eggs with human sperm should not continue to be legal in the U.K. for research purposes,” said Calum MacKellar, the council’s director of research.

“Most people are not aware that these kinds of experiments have been taking place in the U.K. and find it deeply offensive. Parliament should follow France and Germany and prohibit the creation of animal-human hybrid embryos.”

In a report published in 2004, the President’s Council on Bioethics in the United States also advocated prohibiting the creation of animal-human embryos by uniting human and animal eggs and sperm. A draft law introduced in U.S. Congress by Senator Samuel Brownback (R-Kan.) would outlaw the creation of human-animal mixtures.

A 2005 report from the U.K. House of Commons Science and Technology Committee takes a more liberal stance, saying such embryos could be legal for research purposes if they are destroyed within 14 days.

“While there is revulsion in some quarters that such creations appear to blur the distinction between animals and humans, it could be argued that they are less human than, and therefore pose fewer ethical problems for research than fully human embryos,” the committee wrote.

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