Science news in brief

A bird’s-eye view of 9,000-year-old stone ‘gates’

For nearly a decade, David Kennedy marvelled from behind his computer screen at thousands of mysterious stone structures scattered across Saudi Arabia’s desert. Using Google Earth’s satellite imagery, the archaeologist peeked at thousands of burial sites and other Works of the Old Men, created by nomadic tribes thousands of years ago. But he was unable to secure permission to visit the country to observe up close the ancient designs he and amateur archaeologists had studied from their desktops. Last month, after announcing he had identified nearly 400 stone “gates”, Mr Kennedy received the invitation of a lifetime from Saudi officials to investigate the hidden structures from a helicopter.

“From 500 feet, you can see the vital details of structures that are invisible in the fuzzy image on Google Earth,” said Mr Kennedy, who recently retired from the University of Western Australia. Over the course of three days, he snapped more than 6,000 aerial photographs, lifting the veil on the ancient wonders. The structures ranged in shapes and sizes. Some gates were larger than 1,000 feet long and 250 feet wide. He suspects the oldest of the gates may be 9,000 years old and believes they may have been used for farming. ​

Vintage wine from prehistoric Georgia

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Raise a glass to the nation of Georgia, which could be the birthplace of wine. The country, which straddles the fertile valleys of the south Caucasus Mountains between Europe and the Middle East, may have been home to the first humans to conquer the common grape. In a study published on 13 November, researchers found wine residue on pottery shards from two archaeological sites in Georgia dating to 6,000 BC. The findings are the earliest evidence of wine made from the Eurasian grape, which is used in nearly all wine produced worldwide.

“Talk about ageing of wine. Here we have an 8,000-year-old vintage that we’ve identified,” said Patrick McGovern, a molecular archaeologist from the University of Pennsylvania Museum of Archaeology and Anthropology, and lead author of the study in the journal Proceedings of the National Academy of Sciences. The findings push back the previous date for the oldest evidence of winemaking by about 600 to 1,000 years, which Mr McGovern previously identified in Iran. But it does not dethrone China as the location of the earliest known fermented beverage, which Mr McGovern dated to 7,000 BC. That drink, however, was most likely a cocktail consisting of rice, honey, hawthorn fruit and wild grapes, unlike this most recent find which was pure grape wine.

How snapdragons bind bees by colour

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In the Pyrenees Mountains between France and Spain, wild snapdragons bloom each spring. Their petals scream for pollination – with colour, not sound. A bit of bright contrast brushed over the centre of the flower’s lower lip advertises the nectar behind it. Bees follow the patterns and enter the mouths of the snapdragon. On one side of the mountainous landscape, a subspecies of snapdragon has magenta lips with yellow accents. On the other side, another subspecies offers the opposite: yellow lips with magenta accents. Researchers suspect colouration genes from the two subspecies were not mixing, and that natural selection – assisted by bees and their floral preferences – was favouring the survival of both magenta and yellow flowers independently.

But how did the snapdragon cousins create accented patterns that appear to be equally effective in the same environment? To find out how differences in these snapdragons arose, scientists compared the genomes of the subspecies. They found that the magenta-yellow plants and their yellow-magenta mirrors shared most of the plant’s 30,000 genes – but not a handful related to colour. Those genes behaved like artists painting billboards with different techniques and palettes. Bees favoured a couple of patterns and neglected plants with other colour schemes, the researchers believe, selecting for certain genetic combinations.

Extinction event: this pigeon wasn’t streets ahead

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North America was once a utopia for passenger pigeons. When European colonisers first arrived, as many as five billion roamed the continent. When they migrated, they swept across the entire sky. Then, in just a few decades, commercialised and excessively hunted, the birds vanished. A paper published in Science this month sheds new light on why the creatures went extinct so swiftly. Analysing the DNA of preserved birds, researchers found evidence that natural selection was extremely efficient in passenger pigeons. This might have made the pigeons particularly well-suited for living in dense flocks but unable to cope with living in sparse groups once their numbers started to plummet, the authors suggest.

Biologists generally assume that a large population corresponds to high genetic diversity, which acts as a buffer to extinction, said Susanne Fritz, an evolution expert at the Senckenberg Biodiversity and Climate Research Centre in Frankfurt, Germany, who was not involved in the research. But passenger pigeons were so plentiful and so mobile that beneficial genetic mutations spread and detrimental ones disappeared very quickly throughout their population. This caused a loss in overall genetic diversity, which meant less raw material for adapting to human-induced change. The passenger pigeon illustrates that even species with colossal population sizes are not safe from disappearing.

An alarming discovery about chimps

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Three scientists testing wild chimpanzees in Uganda reported in the journal Science Advances that chimpanzees can do something that previously had only been known in humans: they change the way they are communicating to take into account what their audience knows. Catherine Crockford and Roman M Wittig of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, and Klaus Zuberbühler of the University of St Andrews, found when a chimp saw a realistic model of a snake, the animal would make more sounds – called hoos – and go to a greater effort to show where the snake was if it seemed other chimps were unaware of the danger. If it seemed other chimps already knew about the snake, it would make fewer calls.

To run the experiment, researchers put a model snake on a path chimpanzees used. When a chimp came along, before it reached the snake, they would play two different chimp calls – either a “rest hoo” or several “alert hoos”. The rest hoo would be made by a chimp that was resting, not aware of any danger. The alert hoos would indicate the chimp who made it had seen something dangerous, like a snake. So the chimp on the trail would know either that its neighbours were clueless or aware of danger.

Space plane flies like a dream

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If you miss Nasa’s space shuttles, you might like the Dream Chaser. The compact space plane carries no crew but will transport cargo to the International Space Station and conduct other missions in orbit around the Earth. This month, the vehicle completed an important milestone in its development. A helicopter lifted Dream Chaser more than 2.3 miles off the ground, then dropped it. Over the course of one minute, the craft accelerated to 330 mph, made a couple of turns and glided 10 miles to a runway at Edwards Air Force Base in California. It touched down at a speed of 191 mph, rolling 4,200 feet before coming to a stop.

“The vehicle is in perfect shape, no issues,” Mark N Sirangelo, head of Sierra Nevada Corporation’s Space Systems, maker of the Dream Chaser, said in an interview. Mr Sirangelo said he thought no more glide tests would be needed. If Nasa agrees, the very next flight of the Dream Chaser might be a return from orbit two or three years from now at the end of a mission taking cargo to and from the space station. It is to land on the same runway at the Kennedy Space Center in Florida that the space shuttles once used. Last year, Nasa awarded Sierra Nevada a contract for at least six cargo flights.

© New York Times