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.

Take Advantage of Amazon's Early Black Friday Deals on Tech, Kitchen Appliances, and More

Amazon
Amazon

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Even though Black Friday is still a few days away, Amazon is offering early deals on kitchen appliances, tech, video games, and plenty more. We will keep updating this page as sales come in, but for now, here are the best Amazon Black Friday sales to check out.

Kitchen

Instant Pot/Amazon

- Instant Pot Duo Plus 9-in-115 Quart Electric Pressure Cooker; $90 (save $40) 

- Le Creuset Enameled Cast Iron Signature Sauteuse 3.5 Quarts; $180 (save $120)

- KitchenAid KSMSFTA Sifter with Scale Attachment; $95 (save $75) 

- Keurig K-Mini Coffee Maker; $60 (save $20)

- Cuisinart Bread Maker; $88 (save $97)

- Anova Culinary Sous Vide Precision Cooker; $139 (save $60)

- Aicook Juicer Machine; $35 (save $15)

- JoyJolt Double Wall Insulated Espresso Mugs - Set of Two; $14 (save $10) 

- Longzon Silicone Stretch Lids - Set of 14; $13 (save $14)

HadinEEon Milk Frother; $37 (save $33)

Home Appliances

Roomba/Amazon

- iRobot Roomba 675 Robot Vacuum with Wi-Fi Connectivity; $179 (save $101)

- Fairywill Electric Toothbrush with Four Brush Heads; $19 (save $9)

- ASAKUKI 500ml Premium Essential Oil Diffuser; $22 (save $4)

- Facebook Portal Smart Video Calling 10 inch Touch Screen Display with Alexa; $129 (save $50)

- Bissell air320 Smart Air Purifier with HEPA and Carbon Filters; $280 (save $50)

Oscillating Quiet Cooling Fan Tower; $59 (save $31) 

TaoTronics PTC 1500W Fast Quiet Heating Ceramic Tower; $55 (save $10)

Vitamix 068051 FoodCycler 2 Liter Capacity; $300 (save $100)

AmazonBasics 8-Sheet Home Office Shredder; $33 (save $7)

Ring Video Doorbell; $70 (save $30) 

Video games

Sony

- Marvel's Spider-Man: Game of The Year Edition for PlayStation 4; $20 (save $20)

- Marvel's Avengers; $27 (save $33)

- Minecraft Dungeons Hero Edition for Nintendo Switch; $20 (save $10)

- The Last of Us Part II for PlayStation 4; $30 (save $30)

- LEGO Harry Potter: Collection; $15 (save $15)

- Ghost of Tsushima; $40 (save $20)

BioShock: The Collection; $20 (save $30)

The Sims 4; $20 (save $20)

God of War for PlayStation 4; $10 (save $10)

Days Gone for PlayStation 4; $20 (save $6)

Luigi's Mansion 3 for Nintendo Switch; $40 (save $20)

Computers and tablets

Microsoft/Amazon

- Apple MacBook Air 13 inches with 256 GB; $899 (save $100)

- New Apple MacBook Pro 16 inches with 512 GB; $2149 (save $250) 

- Samsung Chromebook 4 Chrome OS 11.6 inches with 32 GB; $210 (save $20) 

- Microsoft Surface Laptop 3 with 13.5 inch Touch-Screen; $1200 (save $400)

- Lenovo ThinkPad T490 Laptop; $889 (save $111)

- Amazon Fire HD 10 Tablet (64GB); $120 (save $70)

- Amazon Fire HD 10 Kids Edition Tablet (32 GB); $130 (save $70)

- Samsung Galaxy Tab A 8 inches with 32 GB; $100 (save $50)

Apple iPad Mini (64 GB); $379 (save $20)

- Apple iMac 27 inches with 256 GB; $1649 (save $150)

- Vankyo MatrixPad S2 Tablet; $120 (save $10)

Tech, gadgets, and TVs

Apple/Amazon

- Apple Watch Series 3 with GPS; $179 (save $20) 

- SAMSUNG 75-inch Class Crystal 4K Smart TV; $998 (save $200)

- Apple AirPods Pro; $169 (save $50)

- Nixplay 2K Smart Digital Picture Frame 9.7 Inch Silver; $238 (save $92)

- All-New Amazon Echo Dot with Clock and Alexa (4th Gen); $39 (save $21)

- MACTREM LED Ring Light 6" with Tripod Stand; $16 (save $3)

- Anker Soundcore Upgraded Bluetooth Speaker; $22 (save $8)

- Amazon Fire TV Stick with Alexa Voice Remote; $28 (save $12)

Canon EOS M50 Mirrorless Camera with EF-M 15-45mm Lens; $549 (save $100)

DR. J Professional HI-04 Mini Projector; $93 (save $37)

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New Online Art Exhibition Needs the Public’s Help to Track Down Lost Masterpieces by Van Gogh, Monet, and More

Vincent van Gogh's original Portrait of Dr. Gachet wasn't stolen, but it hasn't been seen in 30 years.
Vincent van Gogh's original Portrait of Dr. Gachet wasn't stolen, but it hasn't been seen in 30 years.
Vincent van Gogh, Wikimedia Commons // Public Domain

If you wanted to compare both versions of Vincent van Gogh’s Portrait of Dr. Gachet in person, you couldn’t. While the second one currently hangs in Paris’s Musée d'Orsay, the public hasn’t seen the original painting since 1990. In fact, nobody’s really sure where it is—after its owner Ryoei Saito died in 1996, the precious item passed from private collector to private collector, but the identity of its current owner is shrouded in mystery.

As Smithsonian Magazine reports, Portrait of Dr. Gachet (1890) is one of a dozen paintings in “Missing Masterpieces,” a digital exhibit of some of the world’s most famous lost artworks. It’s not the only Van Gogh in the collection. His 1884 painting The Parsonage Garden at Nuenen in Spring was snatched from the Netherlands’ Singer Laren museum earlier this year; and his 1888 painting The Painter on His Way to Work has been missing since World War II. Other works include View of Auvers-sur-Oise by Paul Cézanne, William Blake’s Last Judgement, and two bridge paintings by Claude Monet.

Paul Cézanne's View of Auvers-sur-Oise was stolen from the University of Oxford's art museum on New Year's Eve in 1999.Ashmolean Museum, Wikimedia Commons // Public Domain

The new online exhibit is a collaboration between Samsung and art crime expert Noah Charney, who founded The Association for Research into Crimes Against Art. It isn’t just a page where art enthusiasts can explore the stories behind the missing works—it’s also a way to encourage people to come forward with information that could lead to the recovery of the works themselves.

“From contradictory media reports to speculation in Reddit feeds—the clues are out there, but the volume of information can be overwhelming,” Charney said in a press release. “This is where technology and social media can help by bringing people together to assist the search. It’s not unheard of for an innocuous tip posted online to be the key that unlocks a case.”

The exhibition will be online through February 10, 2021, and citizen sleuths can email their tips to missingmasterpieces@artcrimeresearch.org.

[h/t Smithsonian Magazine]