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Barely Any Land on Earth Is Untouched by Humans

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A new study, published in the journal Proceedings of the National Academy of Sciences (PNAS), suggests that nearly all of the world’s unspoiled nature is entirely gone. In fact, most of it disappeared at least several thousand years ago, thanks to human activity, The Washington Post reports.

Nicole Boivin from the University of Oxford and the Max Planck Institute for the Science of Human History teamed up with scientists from the UK, U.S., and Australia to pore over archaeological, fossil, and ancient DNA data. The researchers concluded that humans began affecting the world’s natural ecosystems long before cars, housing developments, or factories existed. “Pristine’ landscapes simply do not exist and, in most cases, have not existed for millennia,” they said in a release.

The paper outlines the major phases when humans shaped the world and altered our world’s ecosystems: global human expansion during the Late Pleistocene; the Neolithic spread of agriculture; the era of humans colonizing islands; and the emergence of urban trading societies.

Here’s a rough timeline: modern humans arose in Africa roughly 190,000 years ago, and by 50,000–70,000 years ago (some say even earlier) had begun venturing out of the home continent. Human hunting is presumed to have helped drive the extinctions of some types of large or giant animals, called megafauna, in Australia, Tasmania, and later the Americas between 50,000 and 10,000 years ago. One example of our early impact occurred some 20,000 to 23,000 years ago, when humans introduced a new species—a marsupial that lived in New Guinea, now called the northern common cuscus—to Indonesia and other regions in the South Pacific.

Astoundingly enough, all this activity preceded the advent of agricultural societies during the Holocene period, which began about 11,700 years ago. (We still live in the Holocene.) By this time, the human species was widely dispersed throughout the world. Farmers began favoring certain animal, tree, and plant species, which thrive today thanks to our ancestors’ green thumbs. They used fire to burn land for agriculture, and to draw animals out into the open for easier hunting. Humans’ agricultural practices also affected everything from forests (after all, we had to clear land for planting food) to the atmosphere’s greenhouse gas composition. Sometime during this era, livestock and poultry were domesticated and spread from the Near East to across the globe.

Meanwhile, seafaring societies began spreading pests from one island to another, since various species of rats, mice, insects, and lizards stowed away onboard sailors’ boats. As humans colonized these new lands, they also threatened indigenous animals, contributed to deforestation, introduced new crops, generally altered these virgin landscapes for good.

As humanity’s become more advanced, our impact on our environment has grown. During the Industrial Revolution, factory emissions dramatically altered atmospheric carbon dioxide concentrations. In fact, researchers have even argued that these gases mark the end of the Holocene and the beginning of a new geological epoch called the Anthropocene.

In short, humans have a long, long history of affecting and changing the natural world. However, the study’s researchers don’t necessarily think that’s a bad thing. We’ll never be able to undo the damage, but we can mindfully monitor and shape the way we physically impact the world.

“The fact that we’ve been changing the planet for so long, with both positive and negative consequences, suggests that we can try to take control of the transformation, and make it less detrimental,” Boivin told The New Yorker

[h/t The Washington Post]

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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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