The potential power of embryonic and fetal inter-species combinations became clear at the end of the 20th century 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.Because of these and other results, the President's Council on Bioethics of the USA indicated in a report published in 2004 and entitled Reproduction and Responsibility: The Regulation of New Biotechnologies that in the context of actually mixing human and nonhuman gametes or blastomeres at the very earliest stages of embryological development - the ethical concerns raised by violating the human-nonhuman species barrier were especially acute. Thus, the drawing of clear lines limiting permissible research in this area should be specifically considered. Accordingly, the President's Council recommended that one bright line should be drawn at the creation of human-nonhuman embryos, produced by the fertilisation of human eggs by nonhuman animal (for example, chimpanzee) sperm (or the reverse). This is because the Council accepted that society should not be put into a position to judge the humanity or moral worth of such ambiguous hybrid entities (for example, a ‘humanzee’, the analogue of the mule). Moreover, the Council stated that it did not want to see the possibility of a human being having other than human progenitors (for example, having a monkey as a parent). The Council also recommended that the US Congress should draft legislation to address these biological possibilities and make it illegal to cross this line.But in a report entitled Human Reproductive Technologies and the Law prepared in 2005, the UK House of Commons Science and Technology Committee went a lot further than the US President’s Council. For example, it indicated that the fertilisation of nonhuman eggs with human sperm should continue to be legal in the UK for research purposes and the time limit extended before they are destroyed. This position was re-emphasised by the same House of Commons committee in its 2007 report entitled Government Proposals for the Regulation of Hybrid and Chimera Embryos in which the Members of Parliament stated that "the creation of human-animal chimera or hybrid embryos, …, is necessary, for example in the pursuit of knowledge about the genetic basis of disease and the direction of stem cells into future cell-based therapy." As a result of these developments in the creation of human-nonhuman combinations, the Scottish Council on Human Bioethics prepared an extensive report, in 2006, on the ethical issues associated to human-nonhuman inter-species embryos. As one of the first reports in Europe on this topic, it sought to emphasise the ethical complexity and risks relating to such experimentation.