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Wikimedia Commons

Swimming with Giant Sloths

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Wikimedia Commons

Sloths aren’t the most impressive swimmers. When today’s two- and three-toed sloths take a dip, they bob along in an awkward doggy paddle. But there used to be sloths that evolution had specifically adapted to be at home in the water. Over the course of four million years, one lineage of giant sloth shuffled into the seas.

The classic image of a giant sloth is of a bulky mammal lazily plucking leaves in an Ice Age forest. But the swimming sloths—named Thalassocnus—lived along the beaches of Peru between 8 and 4 million years ago. There were no tree stands here for the sloths to waddle among. The sea met the desert, and it was in the waves that the sloths found their food.

Since these sloths were first described from Peru’s Pisco Formation in 1995, paleontologists have identified five Thalassocnus species that lived along the same seaside one right after the other. And, paired with the fact that they were found with marine animals, the skeletons of these sloths suggested that the herbivores were at home foraging in the shallows. From the first species to the last, Thalassocnus looked like a seaside sloth.

But how did Thalassocnus go where no sloth had gone before? In a paper published in the Proceedings of the Royal Society B, paleontologist Eli Amson and colleagues at the Muséum national d'Histoire naturelle, Paris reveal that the secret of Thalassocnus lies inside the beast’s bones.

Compared to other mammals, sloths have unusually dense bones. This was true of the extinct giant sloths, too, and the successive species of Thalassocnus took this feature much further. After cutting into the ribs and limb bones of the first four Thalassocnus species, Amson and coauthors found that the bones of these sloths became increasingly dense until, in cross section, they had almost entirely lost their hollow central cavity. This condition is called osteosclerosis. And more than that, the sloth species show a swelling of some bones called pachyostosis that allowed the mammals to pack more bone tissue on.

Paleontologists have seen these features in other amphibious mammals. The bones of the earliest whales and sea cows—mammals that were caught transitioning into a fully aquatic life—show the same characteristics. And these changes to bones were not pathological. They track the evolution of skeletons as bone ballast.

While lungs filled with air are vital to keep swimming mammals from drowning, they can also be a liability for diving. Big, air-filled lungs buoy submerged animals up. Denser, swollen bones allowed early whales, sea cows, and, yes, giant sloths to more easily achieve neutral buoyancy underwater and therefore use less energy to stay beneath the surface.

Thalassocnus was far from being the Michael Phelps of the sloth world, though. The sloth still retained the familiar, bulky body shape of its ancestors. Instead of becoming a streamlined swimmer, Thalassocnus probably favored a method used by marine iguanas today. Anchored down by hefty bones, the sloth gripped the bottom with huge claws and scooped up soft plants as it wafted in the surf. Sloths slurped seaweed by the sea shore.

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iStock // Ekaterina Minaeva
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Man Buys Two Metric Tons of LEGO Bricks; Sorts Them Via Machine Learning
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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!

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iStock
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Here's How to Change Your Name on Facebook
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iStock

Whether you want to change your legal name, adopt a new nickname, or simply reinvent your online persona, it's helpful to know the process of resetting your name on Facebook. The social media site isn't a fan of fake accounts, and as a result changing your name is a little more complicated than updating your profile picture or relationship status. Luckily, Daily Dot laid out the steps.

Start by going to the blue bar at the top of the page in desktop view and clicking the down arrow to the far right. From here, go to Settings. This should take you to the General Account Settings page. Find your name as it appears on your profile and click the Edit link to the right of it. Now, you can input your preferred first and last name, and if you’d like, your middle name.

The steps are similar in Facebook mobile. To find Settings, tap the More option in the bottom right corner. Go to Account Settings, then General, then hit your name to change it.

Whatever you type should adhere to Facebook's guidelines, which prohibit symbols, numbers, unusual capitalization, and honorifics like Mr., Ms., and Dr. Before landing on a name, make sure you’re ready to commit to it: Facebook won’t let you update it again for 60 days. If you aren’t happy with these restrictions, adding a secondary name or a name pronunciation might better suit your needs. You can do this by going to the Details About You heading under the About page of your profile.

[h/t Daily Dot]

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