So we’ve made sperm. No man necessary.

Nature cuts my last potential for productivity to the quick with news that researchers have made mouse sperm in a dish:

Researchers in China say that they have discovered a way to make rudimentary mouse sperm in a dish, and used them to produce offspring.

If the claim stands up to scrutiny, it could point the way to making human sperm in the lab for fertility treatments. But some scientists are not convinced by the report, which is published today in Cell Stem Cell.

In 2011, molecular biologists led by Mitinori Saitou at Kyoto University reported that they had managed to recreate the first stages of sperm development in a dish2. They coaxed mouse embryonic stem cells to become cells that resembled primordial germ cells (PGCs) — an important stage in the development of both eggs and sperm.

Saitou’s team then implanted the artificial PGCs into a mouse: when implanted in testes, they grew to become sperm; in ovaries, they matured into eggs.

Now, Xiao-Yang Zhao, a development biologist at the Southern Medical University in Guangzhou, and Qi Zhou, a cloning specialist and stem-cell biologist at the Institute of Zoology in Beijing, along with colleagues from Nanjing Medical University, say that they have trumped Saitou’s work by carrying out more of the process in a dish.