Sperm Warfare (Or: Why it Takes 1 Billion Sperm to Make One Zygote)

iStock/Bet_Noire
iStock/Bet_Noire

The average man produces roughly 525 billion sperm cells over his lifetime and releases, in one way or another, more than one billion of them per month and anywhere from 40 million to 1.2 billion in a single ejaculation. The males of other species boast some equally impressive numbers: 280 million, 1 billion and 3 billion per ejaculate for rabbits, sheep and bulls, respectively. If it only takes one sperm cell to fertilize an egg, though, why produce so many?

The Seminal Wars

The females of many species mate with and receive the sperm of multiple males, often in quick succession. Deep in the lady’s nether regions, those sperm compete to fertilize the egg. Now, if you’re serious about winning a lottery or a raffle, you don’t buy just one ticket do you? No, you buy several to increase your probability of winning. Sperm, in a way, are a lot like lottery tickets. If you’re serious about passing on your genes, then you want to get as many sperm as possible near a fertile egg cell. (In other ways, they’re not like lottery tickets at all, and I would discourage you from trying to buy them in gas stations or convenience stores.) For a male, the more of his sperm going up against his rivals’ seed, the merrier.

Sperm competition is such a powerful selective pressure, in fact, that it influences the size of the testes and the volume of ejaculate of some animals and causes others to modulate the amount of sperm they produce based on the presence of a rival male. Male chimpanzees, who face high levels of sperm competition, possess the largest testes among the great apes. Gorillas, who face almost no sperm competition thanks to a rigid social structure where the dominant male alone gets to mate with all the females, don’t need to waste precious energy and resources on sperm production and hence have some downright dinky testes—almost 15 times smaller than chimps’ (relative to their body weight).

Male humans would feel somewhat embarrassed if they were naked in a locker room full of chimps, but still pretty good about themselves if they were naked and surrounded by silverbacks (nervous, too, perhaps). Evolutionary biologists are still trying to work out whether our relatively large testes are leftovers from some point in our evolutionary past, or if sperm competition was at one point an important factor in human reproduction.

It’s not a sprint. It’s a marathon

Sperm competition isn’t a prevalent problem among modern Homo sapiens and guys don’t really need a veritable army of sperm to race someone else’s genes to an egg. We still need an awful lot of those squiggly little cells, though, because even if there’s no other sperm to compete against, every man’s little swimmers still have to fight in a battle of the sexes. Females demand only the finest sperm for their eggs, and the war their bodies wage on sperm is one of attrition.

After insemination, the sperm cells of humans, and many other species, have a long trip ahead of them, relative to their tiny size. At every step of the way, many sperm cells run out of energy or die and their surviving brothers are forced to leave them behind: only a portion of the sperm that are deposited into the vagina make it to the uterus, an even smaller group get to the oviducts and a fraction of those make their way to the upper oviduct where the egg is actually located. Once the sperm reach the egg, things don’t get any easier. One does not simply walk into Mordor. The egg is covered by a thick layer of gelatinous, follicular cells called the cumulus oophorus, which acts as a barrier, and it often takes the assault of several sperm cells to break it down enough for one lucky one to get through and fertilize the egg. Charles Lindemann, who researches the mechanisms of sperm motility at Oakland University in Rochester, Michigan, likens the whole ordeal to a “marathon run in a maze filled with mucus followed by an obstacle course.”

The odds stacked against any single sperm cell making the grueling journey to the egg can be offset by producing a large number of sperm. While just a small fraction of the sperm will reach their destination and do the job they were made to do, having a few million more cells backing them up makes for a pretty good reproductive insurance policy.

This Course Will Teach You How to Play Guitar Like a Pro for $29

BartekSzewczyk/iStock via Getty Images
BartekSzewczyk/iStock via Getty Images

Be honest: You’ve watched a YouTube video or two in an attempt to learn how to play a song on the guitar. Whether it was through tabs or simply copying whatever you saw on the screen, the fun always ends when friends start throwing out requests for songs you have no idea how to play. So how about you actually learn how to play guitar for real this time?

It’s now possible to learn guitar from home with the Ultimate Beginner to Expert Guitar Lessons Bundle, which is currently on sale for $29. Grab that Gibson, Fender, or whatever you have handy, and learn to strum rhythms from scratch.

The strumming course will teach you how to count beats and rests to turn your hands and fingers into the perfect accompaniment for your own voice or other musicians. Then, you can take things a step further and learn advanced jamming and soloing to riff anytime, anywhere. This course will teach you to improvise across various chords and progressions so you can jump into any jam with something original. You’ll also have the chance to dive deep into the major guitar genres of bluegrass, blues, and jazz. Lessons in jam etiquette, genre history, and how to read music will separate you from a novice player.

This bundle also includes courses in ear training so you can properly identify any relative note, interval, or pitch. That way, you can play along with any song when it comes on, or even understand how to modify it into the key you’d prefer. And when the time comes to perform, be prepared with skilled hammer-ons, pull-offs, slides, bends, trills, vibrato, and fret-tapping. Not only will you learn the basic foundations of guitar, you’ll ultimately be able to develop your own style with the help of these lessons.

The Ultimate Beginner to Expert Guitar Lessons Bundle is discounted for a limited time. Act on this $29 offer now to work on those fingertip calluses and play like a pro.

 

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Researchers Discover New Details In Vermeer’s Girl With a Pearl Earring

Johannes Vermeer's Girl With a Pearl Earring, circa 1665.
Johannes Vermeer's Girl With a Pearl Earring, circa 1665.
Art Media/Print Collector/Getty Images

In 2018, the Mauritshuis gallery in The Hague, Netherlands, gathered an international team of researchers to take part in its “Girl in the Spotlight” project, which aimed to unlock the secrets of Johannes Vermeer’s famed Girl With a Pearl Earring, circa 1665.

Their recently published findings reveal many intriguing details about Vermeer’s artistic process and the artwork itself, though the identity of the painting’s enigmatic subject remains a mystery. Using X-rays and other advanced imaging techniques, the researchers discovered Vermeer depicted the girl in front of a faint green curtain—not an empty dark background—and even painted eyelashes on her eyes.

As The Guardian reports, scholars in the past have cited both the lack of eyelashes and the blank background as support for the theory that Vermeer was painting a conceptual, idealized image of a girl, so these newfound features could be evidence that an actual person posed for him in a specific setting. And, according to head researcher Abbie Vandivere, it’s not entirely a bad thing that we still don’t know who that person is.

“It is good that some mysteries remain and everyone can speculate about her. It allows people their own personal interpretation of the girl; everyone feels their own connection with the way she meets your eyes,” she told The Guardian. “The fact that she is still a mystery keeps people coming back and keeps her exciting and fresh.”

While we’re all pondering the puzzling origin of one of the most captivating models in art history, there are plenty of other fascinating revelations from the Mauritshuis investigation to talk about, too. For one, the Dutch artist evidently spared no expense in bringing Girl With a Pearl Earring to life: the raw materials he used to create various colors in the painting came from just about everywhere, including England, Mexico, Central America, and maybe even Asia or the West Indies. Ultramarine, a blue pigment derived from lapis lazuli (an export of what’s now Afghanistan), which Vermeer used for the girl’s headscarf and jacket, was more valuable than gold at the time.

The study also shed light on Vermeer’s painting methods. He began with broad brush strokes of brown and black paint, layering the girl on top of the background, and then made slight adjustments to her ear, the back of her neck, and the top of her scarf.

If “Girl in the Spotlight” has proven anything, it’s that there’s always more to discover about a work of art—and that’s just what the Mauritshuis intends to do.

“Please know that this is not the end point of our research, but an intermediate station,” Mauritshuis director Martine Gosselink said in a press release. “The collaborations are growing, and so is the desire to find out more.”

As you wait for more information to come to light, here are 15 fascinating facts about Girl With a Pearl Earring.

[h/t The Guardian]