Although Buddhist monks and nuns greatly value the principle of "non-harming" any sentient beings, an astonishingly liberal attitude toward stem cell research and human cloning has emerged in Buddhist cultures, including those in Thailand, Sri Lanka, Taiwan, Korea and Japan. It is interesting to note that stem cell research is prominent and abortion loosely regulated in countries with considerable Buddhist influence.
According to the early Buddhist scriptures, new human life begins at conception. But many Buddhist lay people in these countries seem to feel that the Vinaya (early rules for conduct for monks and nuns), where this strict view is espoused, may no longer be applicable in the strictest sense. As in most religions, patterns of conduct, as well as the interpretation of the early scriptures, undergo significant changes. While many Buddhists in the Western countries view any destruction of embryonic life as wrong - regardless of the possibility that a cure for severe diseases like Alzheimer's or critical spinal cord injuries might be found in a distant future - a considerable amount of Asian Buddhists come to a more permissive conclusion.
First of all, Buddhists are not inclined to see a man-made creation as something competing with a "good" nature. There is a very positive attitude toward changing nature's course if it enhances the welfare of all living beings, and more so if it allows medical advancements. Since in some Asian countries suffering caused by severe diseases is a part of everyday life, some Buddhists tend to argue in favor of possible cures, and many are quite open to prenatal diagnosis of inherited diseases in order to prevent further suffering. But they also argue for a better allocation of current therapies at hand, and do not subscribe to research that will only help an elite rich group that can afford high-priced treatment.
Second, Buddhist ethics are not principles to be followed as law. They are not designed as expressions of indisputable human rights or as a consequence of dignity inherent in every human being. Ethics are much more a matter of personal choice; principles like the one of "non-harming" should be followed as guidelines, and in extraordinary circumstances need not be applied in the strictest sense.
Lastly, the circumstances can be evaluated on a grade. The seriousness of killing a human being, therefore, must be considered with additional criteria. The less complex a being (in size, development and sensory abilities), the less positive karma that being has assembled in life. On the other hand, the better the intentions of the one who takes the life of a being, the better the outcome for the greatest number of suffering human beings, the more it is permissible. But, while most Buddhists stick to the view that an embryo's consciousness is already forming, they also express a discomfort with this kind of research.
The discussion has just begun, and - compared to the discourse in Islamic or Christian cultures - is not yet a very intense, scholarly developed or theoretically advanced debate. Due to the characteristics of Buddhist ethics and the form of ethical discourse mentioned above, there will likely be considerable shifts in opinions, probably toward a stricter position, regarding embryonic research in the near future.