Science in brief: A remarkable archaelogical find in Saudi Arabia, and Georgia with an 8,000-year-old Georgian wine

A round-up of science stories from around the world

Natural selection favours the survival of magenta and yellow flowers (Off2riorob)

A bird’s-eye view of Saudi Arabia’s mysterious structures

For nearly a decade, David Kennedy marvelled from behind his computer screen at thousands of mysterious stone structures scattered across Saudi Arabia’s desert. With Google Earth’s satellite imagery at his fingertips, 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 that he and amateur archaeologists had studied from their desktops.

Last month, after announcing he had identified nearly 400 stone “gates,” 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 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.

In Saudi Arabia, he explored 200 sites from the air across the regions of Harrat Khaybar and Harrat Uwayrid. The structures he observed ranged in shapes and sizes, which he describes as gates, kites, triangles, wheels and keyholes.

Of the 400 structures he describes as “gates” that he had identified on Google Earth, Kennedy studied about 40 from the helicopter and found that the structures were not randomly put together. Rather, each long bar was actually made up of two parallel lines of flat slabs placed on their edges facing each other with small stones filling the space in between. “They are much more sophisticated than I was prepared for,” he said.

Some were larger than 1,000ft long and 250ft wide. He suspects the oldest of the gates may be 9,000 years old. He thinks they may have been used for farming purposes.

Huw Groucutt, an archaeologist at the University of Oxford, said the new images can help show how humans societies have modified the landscape.

Nicholas St Fleur

Wine from prehistoric Georgia with an 8,000-year-old vintage

Raise a glass to the nation of Georgia, which could now 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, giving rise to chardonnay, cabernet sauvignon, and thousands of other reds and whites we enjoy today.

In a recent study, researchers found wine residue on pottery shards from two archaeological sites in Georgia dating to 6000BC. 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 McGovern previously identified in Iran. But it does not dethrone China as the location of the earliest known fermented beverage, which McGovern dated to 7000 BC. That drink, however, was most likely a cocktail consisting of rice, honey, hawthorn fruit and wild grapes, unlike this most recent finding which was pure grape wine.

Nicholas St Fleur

How snapdragons beckon bees with more than one colour

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, one subspecies of snapdragon has magenta lips with yellow accents. On the other side, another subspecies offers the opposite: yellow lips with magenta accents. In the land between, hybrid flowers try it all. These hybrid patterns cannot be as effective for attracting pollinators, or you’d see an expanding strip of hybrids.

Researchers suspected colouration genes from the two subspecies were not mixing well, and that natural selection – assisted by bees and their floral preferences – was favouring the survival of both magenta and yellow flowers independently, not the hybrids.

But how did the snapdragon cousins create accented patterns that appeared to be equally effective in the same environment? To find out how colour differences in these snapdragons arose, scientists compared the genomes of the subspecies in a study published this month in Science.

They found that the magenta-yellow plants and their yellow-magenta mirrors shared most of the plant’s 30,000-some genes – but not a handful related to colour. Those genes behaved like artists painting billboards with different techniques and palettes. And nature appeared to respond to the colourful expressions of these genes. Bees favoured a couple of patterns and neglected plants with other colour schemes, the researchers believe, selecting for certain genetic combinations.

Joanna Klein

A population of billions may have contributed to this bird’s extinction

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, the inconceivable happened: 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 and thoroughly. Analysing the DNA of preserved birds, the 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 Center 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.

In the new study, a team of evolutionary biologists compared the genomes of four passenger pigeon specimens from different geographic regions with those of two band-tailed pigeons, a close living relative, and saw signatures of remarkably efficient natural selection in the passenger pigeons.

The researchers found typically high genetic diversity in regions of the genome that tend to get chopped up and rearranged between generations, but extremely low diversity in regions that do not. Under strong natural selection, when beneficial mutations occur in these latter regions that do not get scrambled as much, large swaths of neutral or even slightly harmful DNA get fixed along with the good genes, suppressing genetic variation, said Beth Shapiro, a professor at the University of California, Santa Cruz, and an author of the study.

The passenger pigeon illustrates that even species with colossal population sizes are not safe from disappearing.

Steph Yin

Chimps Tailor Alarms to What Other Chimps Know

Three scientists testing wild chimpanzees in Uganda reported 15 November 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 in Scotland were studying wild chimpanzees in Uganda, so the subject of their communication was snakes. When a chimp saw a realistic model of a snake, the animal would make more sounds – called hoos – and make a greater effort to show where the snake was if it seemed that other chimps in the area were unaware of the danger. If it seemed other chimps already knew about the snake, it would make fewer calls and stay a shorter time at the danger.

To run the experiment, the 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 neighbors were clueless or aware of danger.

Shortly after the researchers played the calls, the chimp on the trail would encounter the realistic model of a snake. After hearing alert hoos, chimps that encountered the snake made their own alert hoo. But chimps that thought their fellows were unaware of the road hazard made more alert hoo calls.

James Gorman

The Dream Chaser space plane takes flight and aces its landing

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 in the years ahead 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 Space Systems, maker of the Dream Chaser, said in an interview.

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.

The Dream Chaser is an autonomous, self-flying spacecraft, and this iteration will not carry any people. Saturday’s test demonstrated that the software that guides the vehicle worked as designed.

Kenneth Chang

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