“Exposure to short duration gravity load changes including microgravity, as sustained in a parabolic flight statistically significantly decreases the sperm motility and vitality of human fresh sperm samples,” the team found, adding that this may have huge importance for any prolonged human settlement missions in space.
“In the future, should humans remain in space for long periods of time with exposure to different microgravity and hypergravity peaks, which could range from months to a number of years, reproduction may pose a problem to be tackled.”
The mechanism by which sperm motility was decreased remains unknown, with further study needed.
Can we please stop pretending that future space colonists will live their whole lives in microgravity? Nobody seriously suggests that as an option, that’s stupid. Countless studies have shown that for proper biological development, humans (and in fact nearly all organisms) need gravity. But for large space stations, spin gravity is actually not that freaking hard. If you can create a large enough station to support a sizable colony, it does not take much more engineering to make it spin.