Although the terms are often confused or used interchangeably, sperm and semen are not the same thing. Semen is the fluid that comes out of the penis, while sperm are the microscopic cells within the semen. Sperm cells are specialized for the task of fertilizing an egg. Semen analysis is considered essential for diagnosis of male infertility, but is not readily available at medical institutions other than those specializing in infertility treatment. 'Fertility specialists take it for granted that the first step in diagnosing male infertility is to perform a semen analysis,' Professor Kobayashi added.

As artificial intelligence and machine learning tools become more accessible, and scientists face new obstacles to data collection (e.g. rising costs, declining survey response rates), researchers increasingly use predictions from pre-trained algorithms as outcome variables. Though appealing for financial and logistical reasons, using standard tools for inference can misrepresent the association between independent variables and the outcome of interest when the true, unobserved outcome is replaced by a predicted value. In this paper, we characterize the statistical challenges inherent to this so-called ``inference with predicted data'' problem and elucidate three potential sources of error: (i) the relationship between predicted outcomes and their true, unobserved counterparts, (ii) robustness of the machine learning model to resampling or uncertainty about the training data, and (iii) appropriately propagating not just bias but also uncertainty from predictions into the ultimate inference procedure.

A 3D filming technique has revealed that human sperm really swim with a corkscrew motion like otters, rather than wiggling like eels due to their'wonky tails'. Developed by scientists led from Bristol, the method has overturned a 350-year-old belief that sperm tails lash'with a snakelike movement, like eels in water.' In fact, the researchers said, this is merely an optical illusion -- one that is a product of seeing the motion under standard, two-dimensional microscopes. Seen in three dimensions, the reproductive cells instead clearly rotate like a corkscrew as they strive to journey towards an egg. The findings could help to better understand and address the causes of male infertility -- which is thought affect around one-in-seven British couples. A 3D filming technique has revealed that human sperm (pictured in this artist's impression) swim with a corkscrew motion, rather than wiggling like eels due to their'wonky tails' 'With over half of infertility caused by male factors, understanding the human sperm tail is fundamental to developing future diagnostic tools to identify unhealthy sperm,' said paper author Hermes Gadelha of the University of Bristol.

Female fruit flies get a boost in their long-term memory after mating thanks to a molecule found in male fly semen. This molecule – called the sex peptide – binds to the sperm of male flies and is passed on to females, where it travels from the reproductive tract to the brain. It was already known that this molecule, which is unique to fruit flies, alters behaviour. After mating, it changes what females prefer to eat and makes them reject future mating partners, for example. It does this by acting on nerve cells, or neurons, located throughout the body.

By way of a break in this polarized era, let's briefly consider the single topic that men and women of every culture and nationality have happily agreed on, from the beginning of time to this very minute -- babies are good. But until astonishingly recent times, nearly every aspect of where babies come from was utterly mysterious. The titans of the scientific revolution had no notion. Leonardo da Vinci did not know, Galileo did not know, Isaac Newton did not know. They knew, that is, that men and women have sex and as a result, sometimes, babies, but they did not know how those babies are created.