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Millions of Years Ago, the Caribbean Flooded the Amazon Rain Forest—Twice

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Long before the trees of today’s Amazon reached for the sky, scientists say, sharks weaved through salty waters there, and mantis shrimp rattled across the flooded forest floor. The researchers published their findings in the journal Science Advances.

Scientists have known for some time now that an area of the western Amazon basin was underwater millions of years ago. The exact source of that water has been the subject of some dispute. Some researchers have envisioned a wide river sweeping down from the Andes, while others say the inundation must have washed inland from the sea. But neither side had compelling evidence to support their ideas—until now.

The researchers studied two nearly-2000-foot-long sediment cores, one taken by an oil company in eastern Colombia, and the other taken across the border in northwestern Brazil by Brazilian Geological Survey. Each was packed with the natural detritus of millions of years of local life.

The bulk of each core told the story of a world on dry land, but within two thin slices—one from about 18 million years ago, another from about 12 million years ago—a glimmer of the sea appeared. The complete cores contained a total of 933 different types of pollen grains. The thin slices included types of pollen only found in salt water.

Bigger clues were yet to come: The researchers also found a fossilized shark tooth and the remains of a mantis shrimp. “It’s a lost ecosystem,” lead author Carlos Jaramillo, of the Smithsonian Tropical Research Institute, told Lizzie Wade in Science.


Carcharhiniformes indet. tooth from the Saltarin core, Carbonera C2 Formation, early Miocene flooding.
Jorge Carillo


A modern Carcharhinus shark, similar to the fossil shark found in the early Miocene flooding.

Lasting a few hundred thousand to a few million years, each flood period was relatively brief from a geological perspective, Jaramillo says. But they weren't so brief that they didn’t completely alter the landscape.

“The life span of a single Amazonia canopy tree is about 200-400 years,” he tells Mental Floss. “Therefore, for thousands of generations, not a single tree could occupy Amazonia. In other words, the immense forest we see today is geologically young.”

The findings came as a surprise even to Jaramillo and his colleagues. He added, “I was of the opinion that there were no floodings, but it turned out I was mistaken!”

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'Lime Disease' Could Give You a Nasty Rash This Summer
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A cold Corona or virgin margarita is best enjoyed by the pool, but watch where you’re squeezing those limes. As Slate illustrates in a new video, there’s a lesser-known “lime disease,” and it can give you a nasty skin rash if you’re not careful.

When lime juice comes into contact with your skin and is then exposed to UV rays, it can cause a chemical reaction that results in phytophotodermatitis. It looks a little like a poison ivy reaction or sun poisoning, and some of the symptoms include redness, blistering, and inflammation. It’s the same reaction caused by a corrosive sap on the giant hogweed, an invasive weed that’s spreading throughout the U.S.

"Lime disease" may sound random, but it’s a lot more common than you might think. Dermatologist Barry D. Goldman tells Slate he sees cases of the skin condition almost daily in the summer. Some people have even reported receiving second-degree burns as a result of the citric acid from lime juice. According to the Mayo Clinic, the chemical that causes phytophotodermatitis can also be found in wild parsnip, wild dill, wild parsley, buttercups, and other citrus fruits.

To play it safe, keep your limes confined to the great indoors or wash your hands with soap after handling the fruit. You can learn more about phytophotodermatitis by checking out Slate’s video below.

[h/t Slate]

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Why Eating From a Smaller Plate Might Not Be an Effective Dieting Trick 
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It might be time to rewrite the diet books. Israeli psychologists have cast doubt on the widespread belief that eating from smaller plates helps you control food portions and feel fuller, Scientific American reports.

Past studies have shown that this mind trick, called the Delboeuf illusion, influences the amount of food that people eat. In one 2012 study, participants who were given larger bowls ended up eating more soup overall than those given smaller bowls.

However, researchers from Ben-Gurion University in Negev, Israel, concluded in a study published in the journal Appetite that the effectiveness of the illusion depends on how empty your stomach is. The team of scientists studied two groups of participants: one that ate three hours before the experiment, and another that ate one hour prior. When participants were shown images of pizzas on serving trays of varying sizes, the group that hadn’t eaten in several hours was more accurate in assessing the size of pizzas. In other words, the hungrier they were, the less likely they were to be fooled by the different trays.

However, both groups were equally tricked by the illusion when they were asked to estimate the size of non-food objects, such as black circles inside of white circles and hubcaps within tires. Researchers say this demonstrates that motivational factors, like appetite, affects how we perceive food. The findings also dovetail with the results of an earlier study, which concluded that overweight people are less likely to fall for the illusion than people of a normal weight.

So go ahead and get a large plate every now and then. At the very least, it may save you a second trip to the buffet table.

[h/t Scientific American]

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