As I understand, the technology exists - but scientists are still debating whether these types of experiments are indeed ethical.
In the UK, experiments of this kind became legal under the Human Fertilisation and Embryology Act 2008.
Following this legal precedent, The Daily Mail newspaper ran a headline which claimed that these type of experiments are already being conducted behind closed doors:
I also believe humans have already been growing human organs intended for transplant using animal hosts. I guess this can be seen as a form of hybrid genetic manipulation.
With restrictions in place on cloning and stem cell research, this seems to be a viable way for scientists to break boundaries.
