Anyone afraid that we're breeding a generation of indolent, pot-smoking slackers has got a little bit less to worry about today, thanks to research from the University of California.
According to the report, the chemical switch that transforms idle sperm into super swimmers has been found.
The discovery could lead to new male fertility drugs for blank shooters and could also go some way to explaining why habitual pot-smokers sometimes have trouble in the gentleman's area, when it comes to getting up off the sofa and making babies.
The reports's lead author, Yuriy Kirichok said: "Zinc keeps sperm not quite active. You can imagine that if you don't have enough zinc, sperm cells could be activated prematurely and may burn out.
Apparently, high levels of zinc is seminal fluid keep the boys in a holding pattern until they get inside the lady parts. Once there, higher Ph levels prompt a frenzy of thrashing akin to the beach clearing scene in Jaws.
But cannabis has the opposite effect to Zinc, making your wrigglers go at full pelt from the off, meaning they're knackered by the time the reach the egg, if they manage to get there at all.