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Study: The First Americans Didn't Arrive by the Bering Land Bridge

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Stone projectile points discovered at Oregon's Rimrock Draw rockshelter. One may be at least 15,800 years old. Image credit: Katrina Lancaster // Bureau of Land Management // CC BY 2.0

For much of the 20th century, scientists believed that the first settlers of the Americas could only have arrived one way. As the conventional story went, an ice-free super highway opened up across the Bering Land Bridge toward the end of the last ice age, allowing people from Eurasia to follow big game like bison and mammoths down through the interior of North America.

New archaeological discoveries have challenged that narrative in recent years. And a study published in the journal Nature offers further evidence that this northerly corridor wasn’t the first route to the continent.

University of Copenhagen researchers Eske Willerslev, Mikkel Pedersen, and their colleagues found that this harsh route only became viable for human migration 12,600 years ago—when the first plants and animals showed up in the region. Meanwhile, archaeologists have ample evidence that people were living in the Americas long before then.

“We know conclusively that human groups were in the interior before that date—perhaps as early as 15,000 calibrated radiocarbon years before present—so it is highly unlikely that they came south through the corridor,” said Michael O’Brien, an anthropologist and current academic vice president of Texas A&M University–San Antonio, who wasn’t involved in the study. “A more likely scenario is that they came south along the Pacific coast.”

For the study, Pedersen and colleagues drilled sediment cores from beneath the frozen surface of two lakes in western Canada: Charlie Lake and Spring Lake. These were among the last areas to lose their ice cover when the two huge ice sheets that blanketed the region (the Laurentide and Cordilleran ice sheets) split during the end of the last glacial maximum, around 15,000 years ago. The retreating ice opened up a path some 1500 kilometers long into the interior of North America.

With the sediment cores, the scientists were able to reconstruct a history of environmental conditions along this route based on algae, pollen and other plant matter, fossils, and ancient DNA trapped in the layers of chilly soil. They concluded that before 12,700 years ago, patchy grass was the only life along the ice-free route. Slowly, plants like sage brush and willow started to change the barren corridor into a steppe landscape. By 12,600 years ago, bison arrived. About 2000 years later, the route started to look more lively as it became populated by jackrabbits, voles, and other small mammals, which were followed by mammoths, elk, and predators like bald eagles. The route likely became impassable for humans and big mammals again about 10,000 years ago, when dense coniferous forests started to grow.

The results of the study suggest the route was only usable between 12,600 and 10,000 years ago. This narrow window is too late to match with the once-prevailing “Clovis First” hypothesis. The Clovis people, who are named after their characteristic fluted stone spearheads first found near Clovis, New Mexico, were thought to have been the first inhabitants of the Americas. The earliest Clovis points show up in the archaeological record about 13,500 years ago. It was long believed that they got here by crossing the Bering Land Bridge sometime before then.

Recently, several before-Clovis sites have been discovered in the Americas. Fossilized feces more than 14,000 years old have been found in Oregon’s Paisley Caves. Stone tools alongside mastodon bones in Florida were recently found to be 14,550 years old. And much further away from northwestern Canada, in southern Chile, humans inhabited Monte Verde at least 14,000 years ago (and possibly even earlier).

Alternate migration routes have been put forth in the past, such as the controversial Solutrean hypothesis, which posits that the first Americans actually came from Europe, not Asia, via a North Atlantic route. But many anthropologists now favor a Pacific coastal route to explain how the first people got to the Americas, though more research is needed to fully understand how these intrepid settlers traveled (perhaps by boat).

“Such a study has been needed for quite some time now,” said Vanderbilt College archaeologist Tom Dillehay, who wasn’t involved in the new study. Dillehay, whose excavations at Monte Verde in the 1970s revealed the site's ancient age, challenging the Clovis First theory—and long considered suspect as a result—told mental_floss that this type of study is just the beginning. “I would like to see more studies of this nature done in other areas of the corridor to confirm this hypothesis—especially at the entrance and exits points of the corridor.”

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iStock // Ekaterina Minaeva
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technology
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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Health
200 Health Experts Call for Ban on Two Antibacterial Chemicals
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iStock

In September 2016, the U.S. Food and Drug Administration (FDA) issued a ban on antibacterial soap and body wash. But a large collective of scientists and medical professionals says the agency should have done more to stop the spread of harmful chemicals into our bodies and environment, most notably the antimicrobials triclosan and triclocarban. They published their recommendations in the journal Environmental Health Perspectives.

The 2016 report from the FDA concluded that 19 of the most commonly used antimicrobial ingredients are no more effective than ordinary soap and water, and forbade their use in soap and body wash.

"Customers may think added antimicrobials are a way to reduce infections, but in most products there is no evidence that they do," Ted Schettler, science director of the Science and Environmental Health Network, said in a statement.

Studies have shown that these chemicals may actually do more harm than good. They don't keep us from getting sick, but they can contribute to the development of antibiotic-resistant bacteria, also known as superbugs. Triclosan and triclocarban can also damage our hormones and immune systems.

And while they may no longer be appearing on our bathroom sinks or shower shelves, they're still all around us. They've leached into the environment from years of use. They're also still being added to a staggering array of consumer products, as companies create "antibacterial" clothing, toys, yoga mats, paint, food storage containers, electronics, doorknobs, and countertops.

The authors of the new consensus statement say it's time for that to stop.

"We must develop better alternatives and prevent unneeded exposures to antimicrobial chemicals," Rolf Haden of the University of Arizona said in the statement. Haden researches where mass-produced chemicals wind up in the environment.

The statement notes that many manufacturers have simply replaced the banned chemicals with others. "I was happy that the FDA finally acted to remove these chemicals from soaps," said Arlene Blum, executive director of the Green Science Policy Institute. "But I was dismayed to discover at my local drugstore that most products now contain substitutes that may be worse."

Blum, Haden, Schettler, and their colleagues "urge scientists, governments, chemical and product manufacturers, purchasing organizations, retailers, and consumers" to avoid antimicrobial chemicals outside of medical settings. "Where antimicrobials are necessary," they write, we should "use safer alternatives that are not persistent and pose no risk to humans or ecosystems."

They recommend that manufacturers label any products containing antimicrobial chemicals so that consumers can avoid them, and they call for further research into the impacts of these compounds on us and our planet.

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