How Climate Change Shaped Human Migration Out of Africa


Climate change has been shaping human existence for a long time. Researchers, who published their findings today, September 21, in the journal Nature, say our prehistoric ancestors dispersed across the globe in waves, inspired by dramatic changes in the world’s climate.

Exactly how and why our distant ancestors found their way through and out of Africa is the subject of much speculation and research. Earlier studies have concluded that Earth’s orbit caused natural and widespread climate changes in the Late Pleistocene epoch 126,000 to 11,000 years ago, and that these changes might have driven Homo sapiens to scatter and spread across the shifting continents.

To test this theory, researchers at the University of Hawaii at Manoa decided to look for clues in the planet’s climate. They created a computer simulation that tracked changes in life—sustaining elements like vegetation, glacier melt, sea level, and temperature—that could have forced humans to get up and go. 

Their results suggest that early humans did indeed spread in waves. In fact, there were distinct cycles of human exit from Africa, the most significant of which happened around 60,000 years ago, according to the data.

Study co-author Tobias Friedrich created this video depicting human dispersal and density from Africa throughout the world from 125,000 years to 1000 years ago. 

There was one unexpected finding: According to this model, around 80,000 years ago there was a small but rapid human migration into Europe. Unlike the rest of the model’s conclusions, this time estimate conflicts pretty significantly with the archaeological record, which puts the first modern people in Europe no earlier than 45,000 years ago.

William Harcourt-Smith is a paleoanthropologist at the American Museum of Natural History. He was not affiliated with the current study. “This sort of modelling, trying to think about the dispersal of modern humans across the globe in a truly biogeographical sense, is to be applauded,” he told mental_floss.

But Harcourt-Smith is not convinced by the new paper’s pushing back of the first human arrival in Europe by some 35,000 years. The evidence for the first entry occurring about 45,000 years ago is sound, he says: “We know this from the fossil record (modern humans look very different from late Pleistocene Neanderthals) and the distinct archaeological markers found only at modern human sites.”

While fascinating, he says, the new paper is “very, very speculative at best” and should be considered a jumping-off point for further research.

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Philippe Huguen, AFP/Getty Images
McDonald's May Be Getting Rid of Its Plastic Straws
Philippe Huguen, AFP/Getty Images
Philippe Huguen, AFP/Getty Images

First Seattle and then the Queen. Could the Golden Arches be next to join the anti-straw movement? As Fortune reports, McDonald's shareholders will vote at their annual meeting on May 24 on a proposal to phase out drinking straws at the company's 37,000-plus locations in the U.S.

If passed, the fast food behemoth would join the ranks of other governments and businesses around the world that have enacted bans against straws in an effort to reduce plastic waste. Straws are notoriously hard to recycle and typically take hundreds of years to decompose.

McDonald's is currently in the process of removing plastic straws from its roughly 1300 outlets in the UK. However, McDonald's board of directors opposes the move in the U.S., arguing that it would divert money from the company's other eco-friendly initiatives, The Orange County Register reports. This echoes comments from the plastic industry, which says efforts should instead be focused on improving recycling technologies.

"Bans are overly simplistic and may give consumers a false sense of accomplishment without addressing the problem of litter," Scott DeFife of the Plastics Industry Association told the Daily News in New York City, where the city council is mulling a similar citywide ban.

If the city votes in favor of a ban, they'd be following in the footsteps of Seattle, Miami Beach, and Malibu, California, to name a few. In February, Queen Elizabeth II was inspired to ban straws at royal palaces after working with David Attenborough on a conservation film. Prime Minister Theresa May followed suit, announcing in April that the UK would ban plastic straws, cotton swabs, and other single-use plastic items.

It's unclear how many straws are used in the U.S. By one widely reported estimate, Americans use 500 million disposable straws per day—or 1.6 straws per person—but it has been noted that these statistics are based on a survey conducted by an elementary school student. However, plastic straws are the fifth most common type of trash left on beaches, according to data reported by Fortune.

[h/t Fortune]

Mario Tama, Getty Images
Hawaii's Kilauea Volcano Is Causing Another Explosive Problem: Laze
Mario Tama, Getty Images
Mario Tama, Getty Images

Rivers of molten rock aren't the only thing residents near Hawaii's Kilauea volcano have to worry about. Lava from recent volcanic activity has reached the Pacific Ocean and is generating toxic, glass-laced "laze," according to Honolulu-based KITV. Just what is this dangerous substance?

Molten lava has a temperature of about 2000°F, while the surrounding seawater in Hawaii is closer to 80°F. When this super-hot lava hits the colder ocean, the heat makes the water boil, creating powerful explosions of steam, scalding hot water, and projectile rock fragments known as tephra. These plumes are called lava haze, or laze.

Though it looks like regular steam, laze is much more dangerous. When the water and lava combine, and hot lava vaporizes seawater, a series of reactions causes the formation of toxic gas. Chloride from the sea salt mixes with hydrogen in the steam to create a dense, corrosive mixture of hydrochloric acid. The vapor forms clouds that then turn into acid rain.

Laze blows out of the ocean near a lava flow

That’s not the only danger. The lava cools down rapidly, forming volcanic glass—tiny shards of which explode into the air along with the gases.

Even the slightest encounter with a wisp of laze can be problematic. The hot, acidic mixture can irritate the skin, eyes, and respiratory system. It's particularly hazardous to those with breathing problems, like people with asthma.

In 2000, two people died in Hawaii Volcanoes National Park from inhaling laze coming from an active lava flow.

The problem spreads far beyond where the lava itself is flowing, pushing the problem downwind. Due to the amount of lava flowing into the ocean and the strength of the winds, laze currently being generated by the Kilauea eruptions could spread up to 15 miles away, a USGS geologist told Reuters.

[h/t Forbes]


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