The evolutionary event that gave you pumpkins and squash
News and notes about science
Dear Watermelon,
It’s been nice hanging out with you over the summer. But the seasons are changing, and it’s time I move on to pumpkins and squash. It’s not you; it’s me. You’re light, and sweet, and perfect for the summer. But as it starts to cool off, I just need the warm spices that go so well with that buttery hunk of pumpkin meat. Don’t be sad. I’ll see you again next summer.
Many of us have gone through these seasonal relationships with plants of the cucurbitaceae family. And although bittersweet, the opportunity to appreciate their diversity wouldn’t have been possible if it weren’t for an ancient event in plant evolution.
About 100 million years ago, the genome of a single melonlike fruit copied itself. Over time, this one ancestor became a whole family of plants with different colors, shapes, sizes, defenses and flavors, such as pumpkins, squash, watermelons and cucumbers, according to a recent paper published in the journal, Molecular Biology and Evolution.
The researchers compared the genomes and evolutionary trees of a number of plants including cucumbers, melons and gourds. Millions of years of environmental changes allowed the fruits to lose genes over time and tailor their own codes to become what we know them as today.
— Joanna Klein
Colliding black holes are detected for the fourth time
In another step forward for the rapidly expanding universe of invisible astronomy, scientists said that on Aug. 14 they had recorded the space-time reverberations known as gravitational waves from the collision of a pair of black holes 1.8 billion light years away from here.
It was the fourth time, officially, in the last two years that astronomers have detected such ripples from the cataclysmic mergers of black holes — objects so dense that space and time are wrapped around them like a glove so that not even light can escape.
In the August event, one black hole with about 31 times the mass of the Sun and another, with 25 solar masses, combined to make a hole of 53 solar masses. The remaining three solar masses were converted into gravitational waves that radiated more energy than all the stars in the known universe. The observation is in line with earlier gravitational wave detections, confirming an evolving view of the cosmic night.
The detection, announced at a G7 meeting of science ministers in Turin, Italy, and in a paper in the journal Physical Review Letters, marked the successful debut of a new gravitational wave detector known as Virgo, built by a European collaboration and located in Cascina, close to Pisa, Italy.
The current observing run ended on Aug. 25. After a year of work improving the sensitivities of their instruments, a new run will begin in the fall of 2018.
— Dennis Overbye
The mystery of the dead bumblebees and the linden trees
The scene: Visitors in the Kew Royal Botanic Gardens near London have reported hundreds, if not thousands of bees, especially bumblebees, sick or dead, beneath fragrant, flowering Tilia trees. Similar reports have been made in other parts of Britain and Europe, as well as the United States — as long ago as the 16th century.
Philip Stevenson, a chemical ecologist at the Kew Royal Botanic Gardens and the University of Greenwich in the United Kingdom, and another researcher, Hauke Koch, set out to solve this bee mystery, scouring the literature for clues. The duo’s proposed explanation was published recently inbiologyletters.
This case is not closed, but here is what the researchers believe following their review: The bumblebees end up relying too much on the Tilia as a food source because they form strong associations with its odor, color or flower shape. It is even possible that nicotine or caffeine, which some evidence suggests is in linden nectar, enhances these associations (as it has for honeybees with citrus and coffee plants). More experimentation is required, but the bees may continue visiting Tilia, perhaps instead of other flowers, even when there is nothing left to eat.
“It takes them too long to realize that’s not a good source of nectar before they drop to the ground,” Stevenson said.
But Stevenson adds that this is only a partial explanation. Any combination of stressors — especially around weak, hungry bees — could be to blame.
— Joanna Klein
How dinosaurs swapped terrifying teeth for bird beaks
The world once trembled before the theropods.
This dinosaur group, which included bloodthirsty killing-machines like the Tyrannosaurus rex and velociraptor, was notorious for sharp, serrated teeth that many used to eviscerate prey and strip flesh clean from bones. But over millions of years, the fearsome beasts evolved into today’s flamboyantly feathered birds, replacing their terrifying teeth with beaks.
How the theropod mouth transformed has long been a mystery, but a study published recently in the Proceedings of the National Academy of Sciences provides insight into a potential evolutionary mechanism behind the transition.
Amy Balanoff, an evolutionary biologist from Johns Hopkins and an author of the paper, described the findings as further “evidence showing the line of evolution from a Tyrannosaurus rex to a pigeon.”
Using fossils and a large comparative analysis of modern animals,balanoffandateamofevolutionary biologists, led by Shuo Wang from the Capital Normal University in Beijing, found that the loss of teeth and the emergence of beaks are connected processes in theropods. As the beak grew across the dinosaur’s face, it also inhibited the growth of teeth, the team suggested. On an evolutionary scale, this transition happened until theropods developed mouths that resembled the bird beaks seen today.
The team also suggested that a protein called bone morphogenetic protein 4, or BMP4, may simultaneously stop teeth from growing in embryos and stimulate the development of a beak. In the developing embryo, the beak originates near the caruncle and then gradually expands backward. But Stiegler cautions that BMP4 is likely not the only factor behind the mechanism, and that additional research is needed to determine the root cause.
— Nicholas St. Fleur
For Neanderthals, growing big brains took more time
We modern humans like to boast about our big brains, but the Neanderthals seem to have had even larger ones.
A recent analysis of a 49,000-year-old skeleton belonging to a Neanderthal child suggests a surprising difference between them and us: Neanderthal brains appear to have grown to maturity more slowly than those of Homo sapiens.
Developing a clearer understanding of the reasons for the similarities and differences in Neanderthal and Homo sapiens growth patterns could help scientists better understand our evolutionary history and how we came to be as we are today.
“What we saw is that it took longer for them to get their big brains,” said Antonio Rosas, a paleoanthropologist from The National Museum of Natural Sciences in Madrid and lead author of the study, which was published recently in Science.
Rosas and his team studied ancient Neanderthal remains recovered from a cave system in Spain known as El Sidrón, where archaeologists have found the remains of more than a dozen individuals, including the child’s mother and younger brother.
The first thing the researchers needed to do with their child specimen was determine how old he was. So they peeked inside his mouth, which had a mix of 30 baby and adult teeth. By cutting into his teeth they were able to use a microscope to count bands in the enamel, which grow similarly to tree rings.
From their investigation they determined the child was almost 8 years old when he died. They did not find any signs on his bones that would have clued them into the cause of his death.
By investigating the boy’s cranium, the researchers found that it was only 87.5 percent the size of a full grown Neanderthal’s cranium. That differs from anatomically modern human children, who at 7 have craniums that are about 95 percent the size of an adult’s.
Because cranium size is a good indicator of brain size, the findings suggest that Neanderthals’ large brains took longer to grow to adult size than our brains do.
— Nicholas St. Fleur
Belgian ‘Indiana Jones’ tries to solve mystery of a WWI submarine
When Tomas Termote, a marine archaeologist, plunged 100 feet into the sea near Belgium this summer, he could barely believe his eyes: In front of him was a German submarine from World War I, with two of its hatches closed and, he suspected, 23 bodies inside.
“I immediately realized this was a German U-boat, and was elated,” said Termote, a 42-yearold World War I buff and wouldbe “Flemish Indiana Jones” who has made more than 5,000 dives in the North Sea in search of shipwrecks. “The submarine was remarkably intact and covered in seaweed, marine plants, and orange, red and yellow flowers with fish swimming by.”
Termote said in an interview that the search for the well-preserved mystery vessel began three years ago, when he noticed something peculiar in the murky image of a shipwreck off the coast of Ostend, in West Flanders.
The wreck had been identified 30 years earlier as a World War Ii-era craft used to transfer soldiers and equipment to land controlled by enemy forces. But to Termote’s trained eye, the craft’s angular shape looked more like a submarine.
He said his suspicions were confirmed in June, when he was granted permission to dive in a busy area of the North Sea and observed that the vessel was, in fact, a UB-II submarine.
Carl Decaluwé, the governor of West Flanders, said in an interview that he had notified the German government about the discovery and that the submarine would be declared a war grave.
— Dan Bilefsky
A deep blue vision of Earth from an asteroid hunter
As it slingshotted past Earth recently at 19,000 mph on its journey to an asteroid, NASA’S Osiris-rex spacecraft took a moment to admire the view — from 106,000 miles away.
A composite image was taken by an onboard camera as the spacecraft flew past the planet. It shows the deep blue of the Pacific Ocean flanked by Australia and the southwestern United States and Baja California.
At the top of the image there are several black vertical streaks, the result of the camera’s short exposure times. According to NASA, the camera’s rapid exposures — less than 3 milliseconds each — are necessary when taking a picture of something as bright as our blue planet, but are not required for taking images of the spacecraft’s dark primary target: the asteroid Bennu.
Osiris-rex is on a mission to collect samples from Bennu and bring them back to Earth. Launched in September 2016, the probe made a quick circle around the sun. To get on the right trajectory for traveling toward the asteroid, it needed to fling past Earth last month. The flyby tilted the spacecraft upward by about 6 degrees, which would put it in the correct position to rendezvous with Bennu in August 2018.
— Nicholas St. Fleur