Scientists in Shanghai have challenged the orthodox medical view that a woman is born with egg cells to last a lifetime and will never generate any new ones. Overthrow of this view could hold major implications for treatment of infertility.

Similar challenges have been made before, but have not been sustained. Earlier this month, however, the same medical doctrine with respect to heart muscle cells  that you die with the same cells you are born with  was shown by a Swedish scientist, Jonas Frisen, to be incorrect: the muscle cells do get replaced, though very slowly, at the rate of 1 percent or less per year.

The Chinese team, led by Kang Zou and Ji Wu of Shanghai Jiao Tong University, worked only with mice, but because of the similarity of all mammalian physiology, any proof that mice could produce eggs after birth would set off a race to prove that people could too.

In essence, the Shanghai researchers say they have detected, in both young and old mice, the germ-line cells that produce unfertilized eggs, or oocytes.