A virus that invaded the genomes of humanity's ancestors millions of years ago now plays a critical role in the embryonic stem cells from which all cells in the human body derive, new research shows.

The discovery sheds light on the role viruses play in human evolution and could help scientists better understand how to use stem cells in advanced therapies or even how to convert normal cells into stem cells.

Embryonic stem cells are pluripotent, meaning they are capable of becoming any other kind of cell in the body. Scientists around the world hope to use this capability to help patients recover from injury and disease.

Researchers have struggled for decades to figure out how pluripotency works. These new findings