A group of scientists led at Salk Institute for Biological Studies, California, on Thursday said they have successfully created the first human-pig hybrid embryo. The scientists added that the research remains in a very early stage. Their research took four long years, and involved around 1,500 pig embryos, reported AFP.

Lead investigator Juan Carlos Izpisua Belmonte told AFP, “The ultimate goal is to grow functional and transplantable tissue or organs, but we are far away from that.” An earlier experiment to create a part-mouse and part-rat embryo was successful, following which researchers hoped that a part-human and part-pig embryo could be developed too.

The scientists first implanted adult human stem cells into pig embryos to create a chimera – an organism that contains cells from two different species. After allowing the implant to grow for up to a month, scientists saw that human cells had begun to form into muscle tissue in the pig embryos. The pregnancy was terminated at 28 days after the human cells had begun to develop, reported CNN. Belmonte, a professor at the Salk Institute of Biological Studies’ Gene Expression Laboratory said it was “an important first step”.

The results were published in the journal Cell and the research was conducted using funding from private donors. However, the experiment is currently ineligible for public funding in the United States, reported the National Geographic.

“These observations also raise the possibility of xeno-generating transplantable human tissues and organs towards addressing the worldwide shortage of organ donors,” the report said. Experts suggest that the human-pig chimera could help create transplantable organs in farm animals, though the ethics of this is still extremely controversial.

The experiments have also stirred a controversy as it could theoretically lead to the creation of animals with human qualities, reported AFP.