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Patch of desert in Egypt that was once the ocean to keep a secret about one of the transformation of the most remarkable evolution."
Thirty-seven million years ago in prehistoric Tethys Ocean, an animal that moves a 15-meter long flexible with mencangah jaw, and sawtooth die and sink to the ocean floor. Over thousands of millennia blanket of sediment built up over the bones of the giant. Then receding sea and seabed turned into desert, the wind began to reap sandstone and stone chips on top of the bones. Slowly the world is changing. The shift in the Earth's crust pushed India into Asia, urging rising Himalayas. In Africa, the first human ancestors straighten up and walk on their hind legs. The pharaohs built the pyramids. Roman Empire rose and fell. In all the while the wind continued its patient excavation. Then one day Philip Gingerich showed up to finish the job.
When the sunset one evening last November, Gingerich, a vertebrate paleontologist at the University of Michigan lay down beside backbone Basilosaurus creature called it. We were in one location in Wadi Hitan, an Egyptian desert. Fossil shark teeth, sea urchin spines, and giant catfish bones scattered on the sand around Gingerich. "I spent so much time in between these sea creatures so soon I'm living in their world," he said as he poked the vertebrae of logs with a brush. "When I look at this desert, I see the ocean." Gingerich was searching for an important part of the anatomy of the creature, and he pressed for time. The light was failing, he had to return to camp before his colleagues worry. Wadi Hitan is a beautiful place, but unforgiving. In addition to the bones of prehistoric sea monsters, Gingerich found the remains of the unfortunate man.
He moved toward the tail bone, check each vertebra with the handle of a brush. Then, he stopped and put down the brush. "Here it is the treasure," he said. While cleaning the sand with her fingers carefully, Gingerich reveal slender piece of bone, length of no more than 20 centimeters. "It's not often we get to see the foot whale," he said, lifting the bone reverently in both hands.
Basilosaurus clearly a whale, but the pope who had two small rear legs sticking out of the pelvis, legs, each for a three-year daughter. Winsome little foot-perfectly formed yet useless, at least for a walk is an important clue to understanding how modern whales that have so successfully adapted swimming machines, descended from land mammals that ever walked on four legs. Gingerich has devoted much of his career to explain the metamorphosis which arguably is the largest in the world of animals. On the way, he has shown that whales, once celebrated by creationists as the best evidence against evolution, may constitute evidence of the evolution of the most elegant.
"Complete specimens like that Basilosaurus Rosetta stone," Gingerich said as we drove back to the field camp. "Complete specimens can reveal how the animal lived much more than fragmentary remains."
Wadi Hitan which literally means "valley of whales" turned out to be very rich in the "pearl" of the sort. Over the past 27 years, Gingerich and his colleagues have found the remains of more than 1,000 whale tail in place and many more are waiting to be discovered. When he returned to the camp, we met with several members of Gingerich's team had just returned from their field work. Shortly thereafter, we discuss the results of their work with a dinner of roasted goat meat, ful madammas (Dieng mashed beans), and rolled bread. Sameh Mohammed, head of the conservation area of Wadi Hitan supervisors have for whales farther eastward and reported several new bone piles-fresh clues to puzzles in the history of nature. Iyad Zalmout Jordanian postdoc and graduate student Ryan Bebej digging whales snout sticking out of the side of a cliff. "We think the rest of the body is inside," said Zalmout.
The ancestors of whales and all other land animals are tetrapods flatheaded, shaped like a salamander who dragged himself out of the sea to the muddy shore about 360 million years ago. In the offspring, a primitive lung gradually improve function, wattle fins turned into feet, and jaw joints are arranged to be able to hear in the air, not in the water. Mammals then became one of the most successful land lovers; at 60 million years ago mammals have dominated the Earth. Pope of the few mammals that evolved back into the sea, remodel their terrestrial body plan can sense, eat, move, and mating in the water.
How to whales accomplished an enormous transformation has baffled scientists as the most genius though. Realizing that the puzzle is one of the major challenges for his theory of evolution by natural selection, Charles Darwin tried to explain the puzzle of whales in the first edition of the Origin of Species. He noted that a black bear had been seen swimming in the lake surface with mouth open for hours, feeding on floating insects. "I see no difficulty in a race of bears being rendered, by natural selection, so that the structure and habits more in accordance with the water of life, with larger and larger mouths," Darwin concluded, "till a creature of the pope." However, the critics ridicule the description aloud and amused, and eventually omitted it from later editions of the book that follows.
Nearly a century later, a leading paleontologist at the 20th century George Gaylord Simpson was also confused in determining the exact location for the pope in an orderly evolutionary tree of mammals. "Overall, cetaceans are mammals of the most bizarre and deviant," remarked peevishly. "There is no proper place for them in the scala naturae. As if they move away to a different dimension with orders or similar to it. "
As for the Saxon antievolusi argue, if science can not explain the transformation of whales, probably because the transformation does not ever happen. They found that land animals began to adapt to aquatic life will soon be half-animal, unable to survive in the water or land. And if the pope really never made this huge transition, where the fossil evidence? "The anatomical differences between whales and land mammals are so great, so of course there are many steps between where creatures have paddled and swam in ancient seas before a whale as we know it appears," wrote the authors of Of Pandas and People, a popular creationist textbooks first published in 1989. "So far this has not been found peralahan form."
Without Philip Gingerich accepted the challenge in the mid-1970s. After earning his Ph.D. at Yale, he began excavating in the Clarks Fork River Basin in Wyoming to document the rise of mammals at the beginning of the Eocene, after the extinction of the dinosaurs ten million a year earlier. In 1975 with the hope to track the migration of mammals from Asia to North America, started fieldwork in middle Eocene formations in the province of Punjab and North-West Frontier (now called Khyber Pakhtunkhwa province) of Pakistan. He was disappointed to find that the 50 million year old sediments targeted were not dry land but the seabed from the eastern edge of the Tethys Ocean. When his team uncovered some pelvic bones in 1977, they jokingly call it "walking whale" -the idea that does not make sense. At that time the most famous fossil whales were considered similar to modern whales, with sophisticated mechanisms for underwater hearing, powerful tails with fin width, and without back legs out of the body.
Then in 1979, a member of Gingerich's team in Pakistan found the skull of a wolf's skull, but have similar bone prominent-and very unwolflike-on the top and sides to support the neck and jaw muscles are strong. Stranger still, the braincase was little bigger than a walnut. Later in the same month, Gingerich found some ancient whale specimens in museums in Lucknow and Kolkata, India. "That's when the tiny braincase started to make sense, because early whales have a large skull and the brain is relatively small," said Gingerich remembers. "I'm beginning to think that this small-brained animals might whales very early."
When Gingerich freed the skull from its matrix of hard red stone in his laboratory at Michigan, he found a clump of dense bone at the base of grape called the auditory bulla, with the peak of the S-shaped bone called the sigmoid process-two anatomical features characteristic of whales and help them hear the water. However, the skull lacked several other adaptations that whales use to hear directionally beneath the waves. He concluded that the animal may semiaquatic, spending significant time in shallow waters, but back ashore to rest and breed.
enemuan whales along the most primitive known-Gingerich named Pakicetus, make Gingerich see whales in a new way. "I'm getting more and more thinking about the huge environmental transition that whales," he recalled. "This creature begins as terrestrial animals and turn into aquatic animals. Since then, I was immersed in the search for a variety of transitional forms in this huge leap from land back into the sea. I want to find all of them. "
In the 1980s Gingerich turned his attention to Wadi Hitan. Together with his wife B. Holly Smith, paleontologists and their colleagues from Michigan, William Sanders, he began to look for whales in the formation of fossils dating back some 10 million years younger than the ocean floor where he found Pakicetus. The trio excavated partial skeletons of fully aquatic whales like basilosaurids and Dorudon smaller, five meters in length. These had a great auditory bullae and other adaptations for underwater hearing; long, streamlined bodies with a long spine; muscular tails to propel them through the water with a strong vertical swing. The area was filled with the skulls of both types of whales. "After being in Wadi Hitan short time, people would feel seeing whales everywhere," said Smith. "And shortly thereafter, one realizes that it is the way it is. We immediately understand that we may not be able to collect all of them, so we started mapping and just dig specimens of the most promising. "
However, only in 1989 the team found the chain that they are looking to connect whales to terrestrial ancestors, discovery, almost by accident. Towards the end of the expedition, Gingerich was working basilosaurids framework when finding the whale knee first known-on feet, located on the animal's backbone at positions far more down than he had expected. Now that the researchers already knew the location of the foot, they revisited a number of popes who have "mapped" and soon found the femur, tibia, and fibula, and a lump of bone that forms the foot and ankle whales. On the last day of the expedition, Smith found a complete set of toes slender, 2.5 centimeters. Seeing the small bones make tears tears. "Knowing that aquatic animals are so big it still has legs, feet, and toes that function, realized what this meant for the evolution of the whale-it's incredible," he recalled.
Though not able to support the weight of the body on the ground basilosaurids, the feet are still no function. They had attachments for powerful muscles, also has a functional ankle joints and complex locking mechanism in the knee. Gingerich speculates that act as stimulants or guides during copulation. "It must be difficult to control what happens on the bottom, on the long, snakelike body that, so far from the brain," he said.
Whatever the usefulness of its little legs basilosaurids, discovery confirms that the ancestors of whales once walked, trotted, and ran on land. However, the ancestral identity remains unclear. Some features of an ancient whale skeleton, especially the cheek teeth are large and triangular looks very similar to those of mesonychids, a group of hoofed Eocene carnivores. (Andrewsarchus great and like hyenas, which is probably the largest carnivorous mammal that ever lived on land, may mesonychid.) In the late 1950s immunologists find traits in whale blood implying that whales descended from artiodactyls, the mammalian order which includes pigs, deer, camels, and other even-toed ungulates. In the 1990s, molecular biologists who study cetacean genetic code concluded that the closest living relative to whales is one specific ungulate, the hippopotamus.
Gingerich and many other paleontologists more confident on the real evidence in the bone than the molecular comparisons of modern species. They believe the pope is mesonychids descent. But to test the theory, Gingerich needed to find a particular bone. Anklebone or astragalus is the most distinctive element of the artiodactyl skeleton, because the double-pulley shape unusual with clear lines at the top and bottom of the spine, such as the strain on the pulley wheel that holds the rope. The shape gives artiodactyls spring and greater flexibility than the single-pulley form found in other quadrupeds (modern pope certainly did not help because it did not have the ankle bone).
Returned to Pakistan in 2000, Gingerich finally saw ankle whales for the first time. His graduate student Iyad Zalmout find a fluted bone amid the remains of a whale that lived 47 million years newly discovered, later named Artiocetus. A few minutes later Pakistani geologist Munir ul-Haq found a similar bone at the same site. At first Gingerich thought the two bones were the single pulley astragalus of right and left foot whale-proof that he was right about the origin of whales. But when he held them side by side, he was confused because the slightly asymmetrical. As he pondered this, twirling the two bones are like a puzzler maneuvers two pieces of the puzzle are problematic, suddenly two bones were attached together to form a perfect double-pulley astragalus. The lab scientists is true.
While walking back to the camp that evening, Gingerich and his team passed a group of village children playing dice with goat astragalus. (Already thousands of years people in different cultures use ankle bone domestic artiodactyls in the game and divination.) Zalmout borrow one and give it to Gingerich, then watched in amusement as his professor spent the rest of the night staring at the whale ankle in one hand and goat ankle on the other hand, noting the resemblance is undeniable. "It was a great discovery, but it upset my applecart," Gingerich said with a wry smile. "However, now we know for sure where the origin of whales and hippos that theory is not science fiction."
Since then Gingerich and a number of other paleontologists complete story of the early popes, tooth by tooth, toe by toe. Gingerich believes the first cetaceans may be similar anthracotheres, sleek browser animals like hippos who inhabit swampy lowlands in Eocene. (An alternative theory proposed by paleontologist Hans Thewissen, that whales descended from animals that are similar to Indohyus, which is similar to prehistoric artiodactyls deer, raccoon that for some of the water.) Whatever the shape and size, the earliest whales appeared about 55 million years ago, like all other modern orders of mammals, over a temperature spike at the beginning of the Eocene world. Various mammals that live along the east coast of the Tethys Ocean, where the waters have a strong appeal evolution: warm, salty, rich marine life, free from water dinosaurs extinct ten million years earlier. By entering into deeper waters to catch various types of new food sources, the initial perandai is slowly growing with a longer snout and sharp teeth that are more suitable for grabbing fish. In 50 million years ago, they have reached a stage that is exemplified by Pakicetus: proficient swimmer quadrupedal, which still roam the land.
By adapting to water, early whales gained access to environments beyond the reach of most other mammals, rich in food and shelter, as well as fewer competitors and predators-perfect conditions for evolutionary explosion. What followed was a strange explosion experiments to be pope, which mostly ended in extinction long before modern times. There is a giant Ambulocetus weighing 725 pounds, with short legs ambush hunters and jaw glutton-like giant saltwater crocodile hairy; Dalanistes, with a long neck and a head like a heron; and Makaracetus the short trunked, curved, and muscular, which may be used to eat mollusks.
About 45 million years ago, the water environment drew whales farther out to sea, becomes clogged and stiff neck to be pushed in the water more efficiently, while the elongated face and sharpened like a bow. The hind legs thickened into a piston; toes stretched and membranes that resemble a giant duck leg with the tip of tiny hooves inherited from ancestors legged animals. Swimming methods improved: The tail is thick and strong growing Some whales shot forward with body movements heave up and down with great force. Selection pressure for efficient force is more suitable for longer backbone and flexible. Nose slid back toward the muzzle crown of the head, into the blowhole. Over time, as the animals dive deeper, their eyes began to move from the top to the side of the head in order to better see the water laterally. Whale ears also become more sensitive to underwater sound, aided by the fat pads that flows along the jaw line, in order to collect vibration like an underwater antenna and channel them to the middle ear.
Although it is in conformity with water, 45 million-year-old pope was still to be shuffled to the beach with webbed fingers and toes, looking for fresh water to drink, to mate, or a safe place to give birth. However, within a few million years, the pope can not turn around again: basilosaurids, Dorudon, and his relatives had never set foot on land, swimming confidently on the high seas and even crossed the Atlantic Ocean to the shores of what is now Peru and the United States south . Animals body was already fully adapted to aquatic lifestyle, front leg shortening and stiffening to become fins to glide, tails broadening at the tip horizontal flukes to create a hydrofoil. Pelvic integral with the spine, so that the tail has a range of vertical movement wider. However, like a talisman of terrestrial life long forgotten, there remains hind legs, complete with knee, foot, ankle, and the fingers are all small, which is no longer useful to run but may be beneficial for mating.
The final transition from basilosaurids to modern whales began 34 million years ago, the sudden cold climate phase, which ended the Eocene. Drop in water temperatures near the Poles, shifting ocean currents and upwelling of nutrient-rich sea water along the west coast of Africa and Europe drew whales into environmental niches completely new and adaptation spur-big brains, echolocation, fat blockers, and in some species, bone filters instead of teeth to stretch krill-exist in today's cetaceans.
Especially thanks to Philip Gingerich, the fossil record of whales now offers one of the show's most amazing Darwinian evolution, not against it. Ironically, Gingerich himself grew up in a strictly principled Christian environment, the Amish Mennonite family in eastern Iowa. (Grandfather farmer and lay preacher.) However, at that time, he did not feel that religion and science contradict. "My grandfather open-minded about the age of the earth," he said, "and never mentioned evolution. Remember, these people are very humble, just express an opinion about the things they are good at. "
Gingerich was surprised that many people still feel that religion and science contradict. On my last night in Wadi Hitan, we walked a bit away from the camp under the dome of a brilliant star. "Maybe I've never been particularly religious," he said. "But I consider my work to be very spiritual. Imagine whales swim around it, how they live and die, how the world has this berubahsemua makes me feel touched something much bigger than yourself, your community, or your everyday existence. "He spread his arms, taking horizon dark and desert sand and wind carved sandstone and whales countless silent. "Here there is no place for religion as much as you want."
