CLOSE
Original image

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

Original image

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.

Original image
iStock // Ekaterina Minaeva
arrow
technology
Man Buys Two Metric Tons of LEGO Bricks; Sorts Them Via Machine Learning
Original image
iStock // Ekaterina Minaeva

Jacques Mattheij made a small, but awesome, mistake. He went on eBay one evening and bid on a bunch of bulk LEGO brick auctions, then went to sleep. Upon waking, he discovered that he was the high bidder on many, and was now the proud owner of two tons of LEGO bricks. (This is about 4400 pounds.) He wrote, "[L]esson 1: if you win almost all bids you are bidding too high."

Mattheij had noticed that bulk, unsorted bricks sell for something like €10/kilogram, whereas sets are roughly €40/kg and rare parts go for up to €100/kg. Much of the value of the bricks is in their sorting. If he could reduce the entropy of these bins of unsorted bricks, he could make a tidy profit. While many people do this work by hand, the problem is enormous—just the kind of challenge for a computer. Mattheij writes:

There are 38000+ shapes and there are 100+ possible shades of color (you can roughly tell how old someone is by asking them what lego colors they remember from their youth).

In the following months, Mattheij built a proof-of-concept sorting system using, of course, LEGO. He broke the problem down into a series of sub-problems (including "feeding LEGO reliably from a hopper is surprisingly hard," one of those facts of nature that will stymie even the best system design). After tinkering with the prototype at length, he expanded the system to a surprisingly complex system of conveyer belts (powered by a home treadmill), various pieces of cabinetry, and "copious quantities of crazy glue."

Here's a video showing the current system running at low speed:

The key part of the system was running the bricks past a camera paired with a computer running a neural net-based image classifier. That allows the computer (when sufficiently trained on brick images) to recognize bricks and thus categorize them by color, shape, or other parameters. Remember that as bricks pass by, they can be in any orientation, can be dirty, can even be stuck to other pieces. So having a flexible software system is key to recognizing—in a fraction of a second—what a given brick is, in order to sort it out. When a match is found, a jet of compressed air pops the piece off the conveyer belt and into a waiting bin.

After much experimentation, Mattheij rewrote the software (several times in fact) to accomplish a variety of basic tasks. At its core, the system takes images from a webcam and feeds them to a neural network to do the classification. Of course, the neural net needs to be "trained" by showing it lots of images, and telling it what those images represent. Mattheij's breakthrough was allowing the machine to effectively train itself, with guidance: Running pieces through allows the system to take its own photos, make a guess, and build on that guess. As long as Mattheij corrects the incorrect guesses, he ends up with a decent (and self-reinforcing) corpus of training data. As the machine continues running, it can rack up more training, allowing it to recognize a broad variety of pieces on the fly.

Here's another video, focusing on how the pieces move on conveyer belts (running at slow speed so puny humans can follow). You can also see the air jets in action:

In an email interview, Mattheij told Mental Floss that the system currently sorts LEGO bricks into more than 50 categories. It can also be run in a color-sorting mode to bin the parts across 12 color groups. (Thus at present you'd likely do a two-pass sort on the bricks: once for shape, then a separate pass for color.) He continues to refine the system, with a focus on making its recognition abilities faster. At some point down the line, he plans to make the software portion open source. You're on your own as far as building conveyer belts, bins, and so forth.

Check out Mattheij's writeup in two parts for more information. It starts with an overview of the story, followed up with a deep dive on the software. He's also tweeting about the project (among other things). And if you look around a bit, you'll find bulk LEGO brick auctions online—it's definitely a thing!

Original image
iStock
arrow
Health
One Bite From This Tick Can Make You Allergic to Meat
Original image
iStock

We like to believe that there’s no such thing as a bad organism, that every creature must have its place in the world. But ticks are really making that difficult. As if Lyme disease wasn't bad enough, scientists say some ticks carry a pathogen that causes a sudden and dangerous allergy to meat. Yes, meat.

The Lone Star tick (Amblyomma americanum) mostly looks like your average tick, with a tiny head and a big fat behind, except the adult female has a Texas-shaped spot on its back—thus the name.

Unlike other American ticks, the Lone Star feeds on humans at every stage of its life cycle. Even the larvae want our blood. You can’t get Lyme disease from the Lone Star tick, but you can get something even more mysterious: the inability to safely consume a bacon cheeseburger.

"The weird thing about [this reaction] is it can occur within three to 10 or 12 hours, so patients have no idea what prompted their allergic reactions," allergist Ronald Saff, of the Florida State University College of Medicine, told Business Insider.

What prompted them was STARI, or southern tick-associated rash illness. People with STARI may develop a circular rash like the one commonly seen in Lyme disease. They may feel achy, fatigued, and fevered. And their next meal could make them very, very sick.

Saff now sees at least one patient per week with STARI and a sensitivity to galactose-alpha-1, 3-galactose—more commonly known as alpha-gal—a sugar molecule found in mammal tissue like pork, beef, and lamb. Several hours after eating, patients’ immune systems overreact to alpha-gal, with symptoms ranging from an itchy rash to throat swelling.

Even worse, the more times a person is bitten, the more likely it becomes that they will develop this dangerous allergy.

The tick’s range currently covers the southern, eastern, and south-central U.S., but even that is changing. "We expect with warming temperatures, the tick is going to slowly make its way northward and westward and cause more problems than they're already causing," Saff said. We've already seen that occur with the deer ticks that cause Lyme disease, and 2017 is projected to be an especially bad year.

There’s so much we don’t understand about alpha-gal sensitivity. Scientists don’t know why it happens, how to treat it, or if it's permanent. All they can do is advise us to be vigilant and follow basic tick-avoidance practices.

[h/t Business Insider]

SECTIONS
BIG QUESTIONS
arrow
BIG QUESTIONS
WEATHER WATCH
BE THE CHANGE
JOB SECRETS
QUIZZES
WORLD WAR 1
SMART SHOPPING
STONES, BONES, & WRECKS
#TBT
THE PRESIDENTS
WORDS
RETROBITUARIES