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Portugal’s Oldest Skull Adds to Puzzle of Human Evolution

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Virtual reconstruction of the Aroeira 3 cranium as seen from the front (A), back (B), top (C), and side (D). Image Credit: Zilhão et al. in PNAS, 2017

 
When archaeologists were digging up the dirt floor at the Aroeira cave in central Portugal in 2014, they were already well on their way to understanding the lifestyle of hunter-gatherers who took shelter there during the Middle Pleistocene.

The researchers had found Acheulean handaxes—the most advanced technology of the day—that were used for cutting, scraping, and butchering. They also found burnt deer bones, suggesting that whoever camped out at this cave 400,000 years ago had the know-how to make fires—then a relatively new human achievement.

Then, at the end of the field season, the excavators unexpectedly struck paleoanthropological gold. They were using demolition hammers to break through the cave’s hard fragmented rock when they chipped a piece of bone.

“Immediately we knew we were dealing with a human fossil,” said University of Barcelona archaeologist João Zilhão, the director of the excavation. His team removed a block of the sediment surrounding the fossil, and preparators in Madrid spent two years carefully revealing a human cranium encased inside. Their findings are reported in the current issue of the Proceedings of the National Academy of Sciences.

It’s exceptionally rare to find human remains from this period. It’s even more rare to find them in a good archaeological context, among artifacts like tools and animal bones. So the discovery of this skull—the oldest ever found in Portugal—is exciting for some paleoanthropologists.

Below, you can see the researchers' discovery, removal, cleaning, and finally restoration of the ancient cranium.

Zilhão et al. in PNAS

 
The prehistoric skull from Aroeira shares some similarities with human fossils of the same era found in Spain, France, and Italy—including some fossils thought to be early Neanderthals, which were just starting to emerge in Europe, and some fossils that had been attributed to another species, Homo heidelbergensis. But the new specimen doesn’t fit neatly into a species category, and could help researchers argue for a diversity of human populations in Europe before the rise of modern humans.

Mental_floss spoke to a trio of experts in human evolution for their take on the current study, which they were not involved in. “This find adds more complexity to the European picture, as we are also seeing in Africa and Asia,” Chris Stringer, a paleoanthropologist at London’s Natural History Museum, says.

University College London paleoanthropologist Maria Martinón-Torres sees the skull as a potential ancestor to the Neanderthal. “I think this finding obliges us to abandon the idea that Neanderthal evolution is a single and lineal process,” she says.

She noted that there are several fossils from similar mid-Pleistocene sites, such as Sima de los Huesos in Atapuerca, Spain and Arago in France, that share some Neanderthal traits but have very different combinations of those traits.

“We see now that there is no linearity in the combination of these traits,” Martinón-Torres says. “This is probably due to the fragmentation and isolation of these populations due to the hard climatic conditions in Europe at that time.” She said that when climatic conditions are harsh, populations can get isolated and evolve their own particular distinctive features. Then, when conditions get better, these groups meet and recombine again. “So for a long period we will find a Neanderthal-like but highly variable population,” she says.

Bence Viola, a paleoanthropologist at the University of Toronto, notes that with the addition of the Aroeira skull we now have a few different humans fossils that look quite different from one another despite being from the same period. He says the new skull seems more primitive than the fossils found nearby at Sima de los Huesos, which, ancient DNA results have shown, represent early Neanderthals. “This cranium makes this scenario of having several different populations in Europe in the middle Pleistocene seem likely,” says Viola, who adds that he would be very interested to see what this specimen’s DNA looks like.

Stringer points out that the skull would be even more illuminating if it weren't missing some key parts, including the back of the cranium: “Unfortunately, this new fossil, interesting as it is, doesn’t have the most useful bits to put it into this puzzle."

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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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Working Nights Could Keep Your Body from Healing
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iStock

The world we know today relies on millions of people getting up at sundown to go put in a shift on the highway, at the factory, or in the hospital. But the human body was not designed for nocturnal living. Scientists writing in the journal Occupational & Environmental Medicine say working nights could even prevent our bodies from healing damaged DNA.

It’s not as though anybody’s arguing that working in the dark and sleeping during the day is good for us. Previous studies have linked night work and rotating shifts to increased risks for heart disease, diabetes, weight gain, and car accidents. In 2007, the World Health Organization declared night work “probably or possibly carcinogenic.”

So while we know that flipping our natural sleep/wake schedule on its head can be harmful, we don’t completely know why. Some scientists, including the authors of the current paper, think hormones have something to do with it. They’ve been exploring the physiological effects of shift work on the body for years.

For one previous study, they measured workers’ levels of 8-OH-dG, which is a chemical byproduct of the DNA repair process. (All day long, we bruise and ding our DNA. At night, it should fix itself.) They found that people who slept at night had higher levels of 8-OH-dG in their urine than day sleepers, which suggests that their bodies were healing more damage.

The researchers wondered if the differing 8-OH-dG levels could be somehow related to the hormone melatonin, which helps regulate our body clocks. They went back to the archived urine from the first study and identified 50 workers whose melatonin levels differed drastically between night-sleeping and day-sleeping days. They then tested those workers’ samples for 8-OH-dG.

The difference between the two sleeping periods was dramatic. During sleep on the day before working a night shift, workers produced only 20 percent as much 8-OH-dG as they did when sleeping at night.

"This likely reflects a reduced capacity to repair oxidative DNA damage due to insufficient levels of melatonin,” the authors write, “and may result in cells harbouring higher levels of DNA damage."

DNA damage is considered one of the most fundamental causes of cancer.

Lead author Parveen Bhatti says it’s possible that taking melatonin supplements could help, but it’s still too soon to tell. This was a very small study, the participants were all white, and the researchers didn't control for lifestyle-related variables like what the workers ate.

“In the meantime,” Bhatti told Mental Floss, “shift workers should remain vigilant about following current health guidelines, such as not smoking, eating a balanced diet and getting plenty of sleep and exercise.”

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