by David Braun
Hard Brain Is a Rare Find
The unusual discovery raises hopes that scientists will find other ancient brains and use them to study how gray matter has evolved, said John Maisey, a paleontologist at the American Museum of Natural History in New York. “The brain … is remarkably soft tissue—brain tissue is mostly water,” Maisey said. “To preserve anything is quite remarkable.”
TRUTH:
THE BRAIN GROWTH OF MODERN SHARKS, RAYS, AND CHIMAERA FISH SLOWS AS THEY AGE, EVEN THOUGH THE REST OF THEIR BODIES CONTINUE TO EXPAND.
Ratfish Ancestor
The fossil was found in an iniopterygian, an extinct ancestor of modern ratfishes, also called “ghost sharks” or chimaeras. The fish are also distant relatives of sharks and rays. Maisey said the ancient fish, which swam in an ocean that once covered the midwestern United States, would have fit in the palm of a human hand. Despite their small size, the fish sported a strange appearance: huge eye sockets, rows of sharp sharklike teeth, tails with clubs, large pectoral fins, and spikes on the tips of their fins.
The fossilized brain of this shark ancestor was the size of a pea. (Photo Credit 10.9)
Fish Brain
The scans revealed the fish had a pea-size brain much smaller than the braincase itself. This is similar to modern sharks, rays, and chimaera fish, whose brain growth slows as they age, even as the rest of their bodies expand.
The iniopterygian’s brain has a large lobe for vision, and the skull has relatively large eye sockets. This suggests the fish “was using its eyes as a major way to locate prey,” Maisey said. In addition, the hearing-related section of the brain is flattened. This reflects the curious arrangement of the iniopterygian ear, which was optimized for side-to-side movement, but not up and down movement.
“It is really a very puzzling fish as to how it would have moved around and what it could have done,” Maisey said. “They are really, really bizarre.”
HAZARDS OF LOVE
Did Love Make Neanderthals Extinct?
A new study claims that Neanderthals were done in by the more successful Homo sapiens. But extinction was not through acts of violence, but acts of love.
Neanderthals may have been victims of love, or at least of interspecies breeding with modern humans, according to a new study.
As the heavy-browed species ventured farther and farther to cope with climate change, they increasingly mated with our own species, giving rise to mixed-species humans, researchers suggest. Over generations of genetic mixing, the Neanderthal genome would have dissolved, absorbed into the Homo sapiens population, which was much larger.
A reconstruction of a Neanderthal female (Photo Credit 10.10)
“If you increase the mobility of the groups in the places where they live, you end up increasing the gene flow between the two different populations, until eventually one population disappears as a clearly defined group,” said study co-author C. Michael Barton, an archaeologist at Arizona State University’s School of Human Evolution and Social Change.
“Normally the first groups who [encounter] a new population are men, hunting parties perhaps. And men, being the way they are—if they meet women from another population, there is bound to be interbreeding.”
Bence Viola
paleoanthropologist, on possible reasons why Neanderthals and humans interbred
Doing What Comes Naturally
Some theories suggest Neanderthals disappeared about 30,000 years ago because the species wasn’t able to adapt to a cooling world as well as Homo sapiens.
Barton tells a different tale, suggesting that Neanderthals reacted to the onset of the Ice Age the same ways modern humans did, by ranging farther for food and other resources. “As glaciation increased, there was likely less diversity in land use, so Neanderthals and modern humans alike focused on a particular survival strategy that we still see today at high latitudes,” Barton said.
“They establish a home base and send out foraging parties to bring back resources. People move farther and have more opportunity to come into contact with other groups at greater distances. The archaeological record suggests that this became more and more common in Eurasia as we move toward full glaciation.”
More frequent contact led to more frequent mating, the theory goes, as the two groups were forced to share the same dwindling resources. “Other things might have happened,” Barton said. “But in science we try to find the simplest explanation for things. This theory doesn’t include massive migrations or invasions—just people doing what they normally do.”
To estimate the effects of the assumed uptick in interspecies mating, Barton’s team conducted a computational modeling study that spanned 1,500 Neanderthal generations. In the end, the model results supported the not entirely new idea that Neanderthals were “genetically swamped” by modern humans.
“Genetic Swamping”
Though it’s a relative underdog among Neanderthal-demise theories, genetic swamping is a well-known extinction cause among plant and animal species. A smallish group of native, localized trout, for example, may lose their genetic identity after a large influx of a different species with which the native fish are able to breed.
“When endemic populations are specialized, and for some reason there is a change in their interaction with adjacent populations, and that interaction level goes up, they tend to go extinct—especially if one population is much smaller than the other,” Barton explained. “In conservation biology this is called extinction by hybridization.”
TRUTH:
DNA EVIDENCE SUGGESTS THAT NEANDERTHALS MIGRATED AS FAR EAST AS SIBERIA.
On the Hunt
Paleoanthropologist Bence Viola said other models have produced different results, and some studies have concluded that relatively little interbreeding occurred. But Viola, of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, is intrigued by Barton’s research.
“From an archaeological and anthropological perspective, this sounds interesting and closer to what I believe—that you can have a lot of interbreeding,” Viola said. “Normally the first groups who [encounter] a new population are men, hunting parties perhaps. And men, being the way they are—if they meet women from another population, there is bound to be interbreeding.”
Barton believes interbreeding caused other distinct human and human-ancestor groups to fade away. “But their genes didn’t disappear,” he added. “And their culture probably didn’t disappear either but was blended into a larger population of hunter-gatherers.”
The Max Planck Institute’s Viola believes interbreeding was a cause—but not the cause. “Neanderthals disappeared around 30,000 years ago, and that was a period when the climate turned colder, and that likely made it physically harder for them to survive,” Viola said. “They also may have been exposed to some type of disease that modern humans brought from Africa and for which they had no immunity.
“Of course these are all things that are very hard to study archaeologically,” Viola added. “So these models are a great tool for investigating ideas.”
T. REX’S TINY ANCESTOR
“Nasty” Little Predator
From Dinosaur Dawn Found
Deadly and dog size, the dinosaur Eodromaeus lived in Argentina 230 million years ago, in the time before dinosaurs dominated. What can we learn from the little monster?
The new species is providing fresh insight into the era before dinosaurs overtook other reptiles and ruled the world, a new fossil study says. “This is the most complete picture we have of a predatory dinosaur lineage—what it looked like at the very beginning,” said study co-author Paul Sereno. “It was small but nasty—this animal was fast.”
“It was very cute; you’d want it as a pet. But it might be best as a guard dinosaur, to keep the dogs away.”
Paul Sereno
paleontologist and study author
Nasty, Brutish, and Short
One of the earliest known dinosaurs, Eodromaeus was only about 4 feet (1.3 m
eters) long and would have barely reached the knees of an adult human. But this unassuming little dinosaur gave rise to the theropods, including Tyrannosaurus rex and the “terrible claw,” Deinonychus, the new study suggests.
Like those fearsome descendants, Eodromaeus had a long rigid tail, a unique pelvis shape, and air sacs in its neck bones that may have been related to breathing—and which add to evidence that theropod dinosaurs eventually evolved into today’s birds.
Hold Me Closer, Tiny Dinosaur
Eodromaeus lived alongside—and now appears to have, in a sense, taken the place of—a very similar dinosaur species, Eoraptor, said University of Chicago paleontologist Paul Sereno, also a National Geographic explorer-in-residence. “If you went back 230 million years ago and one of these creatures flitted by, you’d have to wonder which one it was.”
Sereno and his team once thought Eoraptor was an ancestor of meat-eating dinosaurs. But due to recent analysis of Eoraptor fossils, as well as the discovery of Eodromaeus, he now thinks Eoraptor was an ancestor of the giant, long-necked, plant-eating dinosaurs called sauropods.
“That’s the beauty of dinosaur origins,” Sereno said. “Who could predict that these 10- to 15-pound [4.5- to 7-kilogram] creatures—both looking quite similar but eating different things—would end up evolving into things as disparate as Diplodocus and Tyrannosaurus?”
The reclassification of Eoraptor makes sense, agreed Hans-Dieter Sues, a dinosaur expert at the National Museum of Natural History in Washington, D.C., who was not involved in the study. “One thing that everyone noticed when Eoraptor was first discovered was that the back teeth were very odd-looking for a theropod,” said Sues, also a contributing editor to the National Geographic News Watch blog. “It had these little leaf-shaped teeth in the back, and those are teeth you don’t really find in theropods.”
TRUTH:
THE DINOSAUR EODROMAEUS WAS ABOUT 4 FEET LONG AND WEIGHED 10 TO 14 POUNDS.
Complete Set
Nearly all of the bones of Eodromaeus have been accounted for—considered remarkable for such a small creature. Based on its fossils, scientists think Eodromaeus, like its theropod descendants, stood and ran on two legs and had sharp teeth and grasping claws, which the new dinosaur used to snatch the young of other reptiles.
University of Maryland paleontologist Thomas Holtz agreed that Eodromaeus is likely an early theropod ancestor. “I think they’ve got a good case for it here,” said Holtz, who wasn’t part of the new study. “In terms of characteristics, it does seem to be very, very low in the theropod family tree.”
It’s not too surprising that Eodromaeus and Eoraptor looked very similar, he added. Both shared a common ancestor only about ten million years before, which in evolutionary terms is not a very long time. “The closer we get to the common ancestor, the less time they’ve had to diverge, so they look a lot more like each other,” he said. “If you go back far enough, eventually they’re the same creature.”
An Avian Blueprint
The Eodromaeus had air sacs in its neck bones that might have been used for breathing, which adds to evidence that theropod dinosaurs evolved into today’s birds. Modern birds have complex respiratory systems, with two lungs and up to nine air sacs. Such efficient respiratory systems would have boosted meat-eating dinosaurs’ metabolisms and enable them to be active and effective hunters.
Triassic Paradise
The desolate Valley of the Moon in northwestern Argentina, where fossils of Eodromaeus and Eoraptor were found, was filled with lush forests 230 million years ago, according to study co-author Sereno. “It was a gorgeous environment.”
Eodromaeus and Eoraptor shared this Triassic paradise with various other groups of reptiles, including parrot-beaked reptiles that were distantly related to dinosaurs, protomammals, and a number of large crocodile-like creatures. Studying the shared traits between Eodromaeus and Eoraptor could help scientists paint a picture of the unknown last common ancestor of all dinosaurs, University of Maryland’s Holtz said.
That dinosaur Eve, Holtz said, “was probably bipedal, its hands may have already been adapted for grasping … and its diet may not have been strictly meat or plants.” By contrast, “the first dinosaurs may have been omnivores.”
POISON!
Venomous Dinosaur Discovered
A 125-million-year-old dinosaur had more in his arsenal than just sharp teeth. Researchers believe this guy had venom and shocked its prey like a snake.
Jurassic Park (1993) was packed with pseudo-science, but one of its fictions may have accidentally anticipated a dinosaur discovery announced in 2009—venomous raptors.
Finding the Groove
Though a far cry from the movie’s venom-spitting Dilophosaurus, the 125-million-year-old Sinornithosaurus may have attacked like today’s rear-fanged snakes, a new study suggests. Rear-fanged snakes don’t inject venom. Instead, the toxin flows down a telltale groove in a fang’s surface and into the bite wound, inducing a state of shock.
In Sinornithosaurus fossils, researchers discovered an intriguing pocket, possibly for a venom gland, connected to the base of a fang by a long groove, which likely housed a venom duct, the study says. Sinornithosaurus fangs also feature snakelike grooves in their surfaces.
“The ductwork leading out of the venom gland gave the venom a way to travel to the base of the teeth, where the venom welled up in the grooves,” said study co-author paleontologist David Burnham of the University of Kansas Natural History Museum and Biodiversity Research Center.
TRUTH:
REAR-FANGED SNAKES DON’T INJECT VENOM—THE TOXIN FLOWS DOWN A GROOVE IN A FANG’S SURFACE AND INTO THE BITE WOUND.
“So when they sank their teeth into tissue of the victim, it allowed the venom, which was really enhanced saliva, to get into the wound.”
A Stunning Bite
Turkey-size Sinornithosaurus, which likely had feathers, lived in the forests of what’s now northeastern China, and was a member of the family Dromaeosauridae. Birdlike Sinornithosaurus probably used its longish fangs to put the bite on prehistoric birds, Burnham said. Like rear-fanged snakes and some lizards, the dinosaur probably had nonfatal venom that could shock its victims into a defenseless stupor—allowing Sinornithosaurus to eat in peace.
Burnham’s research was inspired by the 2000 find of another possibly venomous dinosaur fang and by a recent discovery that today’s top lizard predator, the Komodo dragon, has a venomous bite that weakens victims so they can be eaten later.
Though believed to have descended from dinosaurs like Sinornithosaurus, today’s birds are toothless and so lack a venom delivery system (though some birds do have toxic skin and feathers). But Burnham is more interested in where Sinornithosaurus venom ability came from than how it evolved.
“How primitive is venom really? Does it go all the way back to the archosaurs?” he said, referring to reptiles thought to have predated dinosaurs by 30 million years or more. “These are things people haven’t really tested yet.”
Gotcha! A sculpture of Sinornithosaurus millenii dinosaur on the hunt (Photo Credit 10.11)
BIG BUNNY
Giant “Roly-Poly”
Rabbit Fossil Found
The king of the bunnies wasn’t a sleek, supple creature. Paleontologists believe he was a roly-poly beach bum.
The Easter bunny came early in March 2011 for a few scientists working on the Spanish island of Minorca. The team announced the discovery of Earth’s biggest known rabbit species, an oddly unbunny-like giant dubbed Nuralagus rex—“the Minorcan king of the hares.”
King of the Hares
The 26-pound (12-kilogram) prehistoric species was about six times bigger than the common European rabbit, found on most continents, according to an analysis of several bones. Study leader Josep Quintana is no stranger to giant Minorcan rabbit fossils, though it took a while before he knew exactly how big a find he’d uncovered.
“When I found the first bone I was 19 years old, I was not aware what this bone
represented. I thought it was a bone of the giant Minorcan turtle!” said Quintana, a paleontologist at the Institut Català de Palentologia in Barcelona.
TRUTH:
A 53-MILLION-YEAR-OLD RABBIT’S FOOT WAS UNEARTHED IN INDIA.
Odd Body
The animal, which lived about three to five million years ago, had several “odd” features that have never before been seen in rabbits, living or extinct, according to the study. For one, the giant rabbit’s “short and stiff” vertebral column meant it couldn’t bunny hop. And the relatively small sizes of sense-related areas of its skull suggested that the animal had small eyes and stubby ears—a far cry from modern rabbit ears. “I think that N. rex would be a rather clumsy rabbit walking,” Quintana said. “Imagine a beaver out of water.”
Despite its oddities, N. rex has many skull and teeth features found in rabbits—meaning there’s “no question” it’s a rabbit, according to Brian Kraatz, an expert in rabbit evolution at the Western University of Health Sciences in Pomona, California. “Really this is a rather typical rabbit head [albeit large] stuck on an atypical rabbit body,” said Kraatz, who was not involved in the study.
“When I found the first bone I was 19 years old, I was not aware what this bone represented. I thought it was a bone of the giant Minorcan turtle!”