George Church’s lab gets closer to creating human eggs in a dish, and a new startup plans to finish the job

Human eggs are incredibly rare cells. The ovary typically produces only 400 mature eggs across a woman’s life. But biologists in George Church’s lab at Harvard University — a group that’s never content with nature’s limits — just got a step closer toward a technique that could one day allow people to grow eggs on demand.

The approach, known as in vitro gametogenesis, or IVG, would allow scientists to make eggs or sperm from adult stem cells. If scientists are successful, IVG could rewrite the rules of assisted reproduction by giving people with infertility and even same-sex couples the ability to have biological children through in vitro fertilization.

Church’s lab is one of a small number pursuing the controversial research. On Friday, its researchers published a new study in Science Advances showing they could coax adult stem cells into meiosis, the special form of cell division that germline stem cells use to create eggs and sperm, and thus a crucial step towards IVG.

The team only got the cells to go about two-thirds of the way through meiosis, after...