According to a publication from 2017, researchers from the US, Spain and Japan have created chimeric embryos by inserting human embryonic cells into embryos from animal species. The procedure included injecting human cells into embryos taken from cattle and pigs. The injected human cells became an integral part of the embryonic development of the pigs, and part of various tissues. After being injected with the human cells, the embryos were transferred to pig surrogate mothers, where they developed for three to four weeks. Although most of the embryos displayed abnormal development, a few did appear to develop normally. Ostensibly, this research aims, at some point in the distant future, to provide human organs from animal species. The next step in this process would involve the pig embryos being genetically engineered using methods, such as CRISPR-Cas.
What is the problem?
The researchers are claiming that their aim is to fulfil a beneficial medical purpose. However, any real medical benefit is a very far distant prospect. For the immediate future, however, severe negative impacts are very likely. This kind of research will not only increase the number of animal experiments, but humans themselves will increasingly become part of the experiments. The principle of human dignity itself, is at risk. The experiments raise serious ethical questions and expose legal loopholes. For example, even under the strict German law for the protection of human embryos, it is not forbidden to create transspecies embryos by adding human embryonic cells to embryos from animal species, such as pigs. The birth and nurture of such creatures in the lab is not explicitly forbidden, regardless of the extent to which human characteristics are inherited in the animals.
Further adverse developments connected to these experiments could emerge in the rise of new diseases. For example, during embryonic development, endogenous retroviruses might find optimal conditions to adapt to the tissues of both species.