It wasn’t long before he decided to look at his ejaculate – certainly not by chance – and discovered tiny, spinning creatures with tails that he called “animals.”
As scientists have looked from top to bottom under microscopes over the centuries, there is no doubt about what their eyes saw and captured in the films: Sperm bathed by moving their tails from side to side.
Why shouldn’t we trust our eyes? So that is what science believed from now on.
It turns out our eyes were wrong.
“If you want to see a real tail beating, you have to move along with the sperm and rotate with the sperm. So almost like you had to make (the camera) really small and stick it to the sperm head,” Gadelha said.
Gadelha co-authors Gabriel Corkidi and Alberto Darsson of Mexico have developed a way to do this at the Universidad Nacional Autonoma de Mexico. Using state-of-the-art tools, including an ultra-fast camera that can record more than 55,000 frames per second, researchers were able to see that moving from side to side was truly an optical illusion.
In reality, the sperm tail is tied on one side only.
That one-sided stroke should force the sperm to float in an eternal circle, Gadelha said. But no, sperm were smarter than that.
“Human sperm have figured out if they swim by swimming, much like playful otters squeezed through water, their one-sided blow will moderate away, and they will swim forward,” said Gadelha, a fertility math expert.
“Sperm rotation is something that is very important. It allows sperm to regain symmetry and actually be able to move straight,” he said.
Gadelha said the findings were a real surprise, so the team spent nearly two years repeating the experiment and cross-checking the math. Results: Like the Earth turned out not flat, the semen really does not fly like snakes or eels.
So why is this important?
“It may be that the rolling motion hides some subtle aspects of the health of this sperm or how well it can travel quickly,” Gadelha said.
“These are all hypothetical questions. We hope more scientists and fertility experts will be interested and ask, ‘Okay, how does this affect infertility?'”
As for what seems contrary to the assumptions of 300 years of science, Gadelha is modest.
“God, I always feel deeply that I’m always wrong,” he said.
“Who knows what we’ll find next? It’s a measurement provided by an instrument with flaws. At the moment, we’re right, but as science progresses, we can make mistakes again. And, hopefully, it will be something very exciting to learn in the next few years.”