The hamster test : Not a precursor to animal-human hybrid embryos

The Hamster Test was devised as part of investigation into male infertility, and entails the mixing of human sperm with eggs from the golden hamster, to test sperm motility.

This Test was permitted under the UK’s 1990 Human Fertilisation & Embryology Act, and is much quoted to justify current controversial proposals to allow the creation of animal-human hybrid embryos.

It is argued that this particular Rubicon was crossed 18 years ago, and on this basis two licences for the creation of animal-human hybrid embryos were issued by the Human Fertilisation & Embryology Authority (HFEA), even before the issue was debated in Parliament.

Amendments to the 1990 Act are currently before the UK Parliament and the animal-human hybrid issues continue to elicit grave concern both nationally and internationally.

The precedent of the hamster test as a justification for the creation of animal-human cloned embryos is a sloppy and deliberately devious association which CORE deconstructs in this statement.

Fact 1

The hamster test was devised to test sperm efficiency in egg penetration not fertilisation.


It is absolutely misleading to suggest that this test has true parallels with current proposals to create animal-human embryos.

The first reference is from the ‘A textbook of in vitro fertilisation and assisted reproduction : The Bourn Hall guide to clinical and laboratory practice’, edited by Peter R Brinsden, published in 1999 by Parthenon Publishing, in the chapter on male infertility by David Mortimer.

After explaining that nowadays (1999) this test is only used in a limited number of laboratories, Mortimer goes on to explain the test is used to assess

‘the ability of spermatazoa to capacitate in vitro and undergo the acrosome reaction which leaves them in a fusogenic state able to bind to and fuse with the hamster oocyte oolemma. The sperm head is then incorporated into the oocyte and its nucleus decondenses to form a swollen sperm head, whose visualisation is the end of the test.’

A further explanation of the rationale behind the hamster test can be found in ‘Human Fertilisation & Embryology’, (2001) by Robert G. Lee and Derek Morgan.

‘The hamster is at present the only known animal amenable to such a test. The zona pellucida of the ovum and the tip of the sperm are species specific. Whereas very closely related species such as the horse and the donkey can interbreed, the hamster is the only known exception to possess a removable zona pellucida which would otherwise repel the sperm from another species. The hamster zona can be removed following treatment with an enzyme, and what has become known as the zona free hamster oocyte penetration test performed.’

We were interested to know if the test had been used in Germany, as we knew that they would be very opposed to the creation of any form of animal-human hybrid. German colleagues told CORE that no embryos were created; in fact that when the test was used in their laboratories it was possible to use the same egg twice, which was an important economic factor as the hamsters were expensive to raise. Obviously no embryos ever developed and were never intended to. That was in fact the reason that the hamster was used and not closely related species which might have reached embryo stage.

The Americans also talk of multiple use of the same eggs. The following is a quote from an American IVF website (the test is still used in some US clinics):

‘The zona-free hamster egg-human sperm penetration assay is a test used to evaluate the ability of the sperm to penetrate an egg. It is also an indicator of the number of sperm required for fertilization in the in vitro fertilization procedure. Techniques are utilized to enhance penetration if the value is low. Hamsters are injected with hormones to produce many eggs; the eggs are collected and the outer egg membrane dissolved with chemicals. After the sperm sample has been prepared with special techniques, it is added to approximately 30-50 eggs. Many hours later the eggs are examined for penetration by the sperm. The human sperm does not fertilize the hamster eggs.

Fact 2

No licences for the hamster test have been applied for in the UK since 2001 (information obtained under Freedom of Information Act).


This is not at all surprising. Modern technology has devised more streamlined and reliable ways of assessing sperm motility and quality, and the process of ICSI (where sperm is inserted directly into the human egg) often bypasses the need for any testing anyway.

Fact 3

It remains illegal in UK law to allow any entity created in this way to develop past the two-cell stage, and it would be criminal to allow it to develop further.


This reaffirms the true nature of the test, which was never intended to legitimise the creation of interspecies embryos.

It highlights the absolute prohibition on allowing any possible subsequent development of an animal-human embryo following the test.

CORE has also been told that hamster eggs were considered particularly suitable for this test because of their inability to continue development past penetration, due to the incompatibility of this animal with the human species. If eggs from primates were used, full fertilisation might have been a real and undesirable possibility.

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