A group of scientists spent almost two years repeating an experiment and verifying the figures.The results held up: Just as the Earth turned out not to be flat, sperm don't really swim like snakes or eels.(CNN in Spanish) - More than 340 years ago, a Dutchman named Antonie van Leeuwenhoek invented a powerful new compound microscope and accidentally discovered the existence of bacteria, a groundbreaking achievement that changed the course of medicine.Not long after, he decided to watch his ejaculate—definitely not by accident—and discovered little wagging creatures with tails he called "animalcules."These creatures "moved forward due to the movement of their tails like those of a snake or an eel swimming in the water," van Leeuwenhoek wrote to the secretary of the Royal Society of the United Kingdom in 1678.Read also: The United Kingdom will allow the freezing of eggs, sperm and embryos for up to 55 yearsThe tail of a man's sperm, he added, "wags with a movement like that of a snake."Antonie van Leeuwenhoek, who invented the compound microscope, was the first to observe the movement of human sperm (his own).As scientists throughout the centuries continued to look down from their microscopes, there is no doubt what their eyes saw and recorded on film: sperm swim by moving their tails back and forth.And why shouldn't we trust our eyes?So that's what science has believed ever since.Turns out our eyes were wrong.Now, using state-of-the-art 3D microscopy and doing the math, a new study says we've actually fallen victim to the "sperm hoax."“Sperm are very cheeky creatures.Our new research using 3D microscopy shows that we have all been victims of a sperm hoax," said study author Hermes Gadelha, head of the Polymathys Laboratory in the Department of Engineering Mathematics at the University of Bristol in the UK. .3D rendering of a sperm head.“If you want to see the true tail slapping, you have to move with the sperm and rotate with the sperm.So it's almost like you need to make a really small (camera) and stick it to the head of the sperm," Gadelha said.Also read: Innovative female contraceptive: Scientists train antibodies to catch 99.9% of spermGadelha's study co-authors Gabriel Corkidi and Alberto Darszon of the National Autonomous University of Mexico developed a way to do this.Using state-of-the-art tools, including a super-high-speed camera that can record more than 55,000 frames per second, the researchers were able to see that the side-to-side movement was actually an optical illusion.In reality, a sperm's tail only wiggles on one side.That one-sided hit should make the sperm swim in a perpetual circle, Gadelha said.But no, sperm are smarter than that."Human sperm figured out that if they rolled while swimming, like playful otters spiraling through water, their one-sided motion would average out and they would swim forward," said Gadelha, who is an expert in the mathematics of fertility.“The rotation of the spermatozoa is something very important.It's something that allows the sperm to regain a symmetry and really be able to go in a straight line,” he said.Instead of side to side, the sperm spirals.The movement is very similar to the way otters spin in the water while playing.The findings were a real surprise, Gadelha said, so the team spent nearly two years repeating the experiment and checking the math.The results held up: Just as the Earth turned out not to be flat, sperm don't really swim like snakes or eels.This 2D animation of a swimming sperm illustrates what it looks like when looking through a microscope."It could be that the rolling motion hides some subtle aspects about the health of these sperm or how well they can travel quickly," Gadelha said.“These are very hypothetical questions.What we hope is that more scientists and fertility experts will take an interest and ask, 'OK, how does this influence infertility?'” he explained.Sperm tricked us into not actually moving like we've believed for centuries, says new study https://t.co/qnTwRuxtaB pic.twitter.com/8pZqHz9fvO– CNN in Spanish (@CNNEE) August 2, 2020As for what it feels like to reverse more than 300 years of scientific assumptions, Gadelha is modest."Oh, God, I always have a deep feeling inside that I'm always wrong," he said.“Who knows what we will find next?This is a measurement given by an instrument that has its limitations.We are right at this point, but we could be wrong again as science advances.And hopefully it will be something very exciting that we will learn in the next few years,” he added.