US agency lifts ban on funding human–animal hybrids

The new rules shorten the developmental window during which human cells can be introduced into non-human primate embryos, disallowing it before development of the central nervous system. This is intended to limit the number of human cells that would make up the chimaera’s brain. They also prohibit breeding animals with human cells, so as to prevent a human-like embryo from growing in a non-human womb, or the birth of an animal that is more humanized than its parents.

http://www.nature.com/news/us-agency-lifts-ban-on-funding-human-animal-hybrids-1.20379?WT.ec_id=NEWSDAILY-20160805