How human eggs stay fresh for decades

In human beings, egg cells need to survive for about five decades, much longer than most other cell types – and they may achieve this unusually long lifespan by slowing down their natural cell processes

By Meagan Mulcair

16 July 2025

Egg cells don’t dispose of their waste the same way other cells do

Sebastian Kaulitzki / Alamy

Human eggs seem to dispose of their waste more slowly than other cells do, which may help them avoid wear and tear – and explain why they live longer.

Every woman is born with a finite number of egg cells, or oocytes, which need to survive for about five decades. For cells, that’s an unusually long time. Although some human cells, like those in the brain and eyes, can live as long as you do, most have much shorter lifespans, in part because the natural processes that allow them to function also damage them over time.

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Cells must recycle their proteins as a form of necessary housekeeping – but it comes at a cost. The energy consumed in this process can generate molecules called reactive oxygen species, or ROS, which cause random damage in the cell. “This is damage happening in the background all the time,” says Elvan Böke at Center for Genomic Regulation in Spain.  “The more ROS there is, the more damage there’s going to be.”

But healthy eggs seem to avoid this issue. To find out why, Böke and her colleagues studied harvested human eggs under a microscope. The cells were placed in a liquid with fluorescent dyes, which bind to acidic cellular components, called lysosomes, that behave as “recycling plants”, says Gabriele Zaffagnini at the University of Cologne in Germany.

The bright dye revealed the waste-disposing lysosomes in human eggs were less active than the same components in other human cell types or those in the egg cells of smaller mammals, like mice. Zaffagnini and his colleagues say this may be a form of self preservation.