Headline, July 05 2022/ EVOLUTION : ''' '' TODAY'S BIRDS TOGGLE '' '''

EVOLUTION : 

''' '' TODAY'S BIRDS

 TOGGLE '' '''

CHARTING A LONG COUNTDOWN TO TAKE OFF : WELCOME to The World Students Society - the exclusive ownership of every student in the world. 150 millions-year journey for feathered dinosaurs to become today's birds.

IN 1993 - '' JURASSIC PARK '' - HELPED INSPIRE 9-year-old student Stephen Brusatte to become a paleontologist. So Dr. Brusatte was thrilled to advise the producers of last year's '' Jurassic World : Dominion '' on what scientists had learned about dinosaurs since he was a child.

He was especially to see one of the most important discoveries make it on the screen : dinosaurs that sported feathers. But judging from the emails he had been receiving, some moviegoers did not share his excitement.

'' A lot of people thought it was made up,'' said Dr. Brusatte, a professor at the University of Edinburgh. '' They thought it was a filmmaker trying to do something crazy.''

Far from crazy, feathered dinosaurs have become a well-established fact, thanks largely to a trove of remarkable fossils that have been unearthed in northeast China since the mid-1990s.

Now Dr. Brusatte and other paleontologists are trying to determine exactly how feathered dinosaurs achieved powered flight and became the birds that fly overhead today - an evolutionary mystery that stretches back more than 150 millions years.

The first big clue to the origin of birds came in 1861, when quarry workers in Solnhofen Germany, found a spectacular fossil of a 145-million-year-old bird that came to be called Archaeopteryx. It had feathered wings like living birds, but also had traits found in reptiles, such as teeth, claws and a long bony tail.

Charles Darwin, who had published ''On the Origin of Species'' two years earlier was delighted. Archaeopteryx looked like what Darwin would have predicted if birds had evolved from reptilian ancestors. '' It's a grand case for me,'' he told a friend.

GRAND as it might have been, Archaeopteryx did not close the case. It did not, for example, reveal which group of reptiles gave rise to birds, nor did it track how those ancestors evolved wings from nothing.

In the 1970s, John Ostrom, a paleontologist at Yale University, identified similarities in the skeletons of birds and ground-running dinosaurs called theropods, a group that includes the Velociraptor and the Tyrannosaurus rex.

But no theropod fossils preserved wings, let alone feathers.

Without more evidence, Dr.Ostrom and other paleontologists argued fiercely about the origin of birds for decades.

In 1996, Pei-ji Chen, a paleontologist from the Nanjing Institute of Geology and Paleontologist in China, came to a paleontology meeting at the American Museum of Natural History in New York, where he handed a packet of photographs to Dr. Ostrom.

The picture showed a fossil of a dinosaur with a fringe of what looked like rudimentary feathers. Dr.Ostrom was so astonished he had to sit down.

The 125-million-year-old fossil, now known as Sinosauropteryx prima, came from Liaoning Province in northeastern China. It was exquisitely preserved in a Pompeii-like blanket of ash. Since then, a steady stream of feathered dinosaur fossils has emerged from the region.

'' There are many thousands of feathered dinosaurs now,'' Dr. Brusatte said.

As more fossils emerged, paleontologists realized that theropods were not the only dinosaurs with feathers. Other species had simple versions, which looked more like wires than the complex network of interlocking filaments found in bird feathers today.

Paleontologists now suspect that the ancestors of all dinosaurs had feathers. And recent discoveries hint that feathers preceded dinosaurs.

The closest relatives of dinosaurs were pterosaurs, which flew like bats with membranes, stretching from their hands to their sides. It turned out they had simple feathers, too.

The first simple feathers may have originally served as insulation. The largest dinosaurs may have been able to use the large volume of their bodies to retain heat, which is why they appear to have lost feathers - just as elephants have lost most of their hair.

In theropods, on the other hand, more elaborate feathers evolved. Some resembled fuzzy down. Others evolved complex feathers that could form sheets - the first wings.

Theropods could not use their early wings to fly. Some horse-size species sported wings the size of laptop screens. Dr. Brusatte speculated that dinosaurs used these more elaborate feathers as display during courtship.

By 160 million years ago, theropods had exploded into a bizarre menagerie of feathered forms. Julia Clarke, a paleontologist at the University of Texas, and her colleagues have studied fossils discovered in Hebei Province in China of a stunning and bizarre species called Calhong Juji.

Fossilized pigments in the feathers suggest that its body was black, while its head and shoulders were an iridescent rainbow. It's hard to figure out how Caihong juji used its feathers. Modern birds have asymmetrical feathers on their wings, which help steer the flow of air to generate lift. But Caihong juji had asymmetrical feathers only on its tails. 

Theropods may have initially used their feathers to generate lift as they ran. That ability might have allowed them to climb slopes faster, or even scale the sides of trees.  

Caihong juji lacked the muscles for powered flight like birds, but they might have jumped and glided in ways scientists have yet to figure out. 

The Honour and Serving of the Latest Global Operational Research on Evolution and Nature, continues. The World Students Society thanks author Carl Zimmer.

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