How Life's Pioneers Got Started

Prehistoric animals were so bizarre, paleontologists often spend years trying to reconstruct their improbable look and lifestyle—only to get it wrong. Two recent investigations scramble our thinking about how the earliest animals first migrated onto land and into the air.

By Susan Kruglinski|Saturday, January 21, 2006
RELATED TAGS: DINOSAURS, ARCHAEOLOGY

Learning to Fly

Sometimes it seems as if human engineers spend their lives rediscovering solutions that evolution arrived at long ago. Take, for example, Microraptor gui, a feathered flying dinosaur that may have flown like the biplane piloted by Orville and Wilbur Wright, 125 million years before they took off from Kitty Hawk.

A Chinese fossil digger found Microraptor in the Liaoning Province two years ago and immediately noticed that the unusual creature, unlike other flying reptiles, had two sets of wings. Scientists initially speculated that it moved through the air like a dragonfly, holding its wings one behind the other. But when paleontologist Sankar Chatterjee of Texas Tech University and aeronautical engineer Jack Templin tried to model such a flight pattern on a computer, the simulated Microraptor quickly crashed.

The only way the animal could remain airborne, the researchers found, was if it had split-level wings, like those of a biplane. With this anatomy, the tree-dwelling animal could jump from a high branch and glide half the length of a football field without flapping. This fits well with the theory that flying dinosaurs evolved from tree dwellers that parachuted to the ground, which then gave rise to gliders and eventually to flappers who could perform powered flight.

The similarity between some of the earliest dinosaur flyers and some of the earliest flying machines is probably more than coincidence. "Biplanes give stability, whereas monoplanes give speed and maneuverability," Chatterjee says. He points out that this progression of abilities makes sense for any kind of evolution, whether it be Darwinian or technological.

Learning to Crawl

Scientists have long supposed that the first vertebrates to emerge from the sea 360 million years ago slithered onto shore like fish with legs. New evidence shows some may actually have romped onto land like lumbering seals. The insight came after paleontologists at Uppsala University in Sweden took a fresh look at Ichthyostega, commonly thought to be among the first animals on land. Per Ahlberg and his colleagues found previous researchers had incorrectly configured the creature's spine. Instead of a uniform column of bones that wags back and forth, it had a contoured spine that could probably move only up and down. "A salamander or a lizard undulates from side to side the same way a fish moves through the water, so one would reasonably expect that in Ichthyostega too," says Ahlberg. But the bones suggest the ancient creature must have moved by arching and relaxing its back.

With stumpy front legs holding up its body and flippers at the rear pushing it forward, Ichthyostega probably shuffled. Its gait may have more closely resembled a seal's flopping or the bow-back capering of a squirrel than the sideways swagger of a gecko. "This is unexpected," says Ahlberg. "The backbone is startlingly reminiscent of what you see in mammals. Yet the animal in other respects is nothing like a mammal."

Despite its seemingly precocious abilities, Ichthyostega went extinct, and its method of locomotion vanished for 100 million years, suggesting that there may be other, yet unknown ways that early animals made their way onto land.

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