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5 December 2013 11:26 am ,
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An animal rights group known as the Nonhuman Rights Project filed lawsuits in three New York courts this week in an...
Researchers have been hot on the trail of the elusive Denisovans, a type of ancient human known only by their DNA and...
Thousands of scientists in the Russian Academy of Sciences (RAS) are about to lose their jobs as a result of the...
Dyslexia, a learning disability that hinders reading, hasn't been associated with deficits in vision, hearing, or...
Exotic, elusive, and dangerous, snakes have fascinated humankind for millennia. They can be hard to find, yet their...
Researchers have sequenced and analyzed the first two snake genomes, which represent two evolutionary extremes. The...
Snake venoms are remarkably complex mixtures that can stun or kill prey within minutes. But more and more researchers...
At age 30, Dutch biologist Freek Vonk has built up a respectable career as a snake scientist. But in his home country,...
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10 May 2002 (All day)
About 40 million or 50 million years ago the ancestors of today's dolphins and whales gave up their landlubbing ways and plunged into the sea. A team of researchers now says that the balance-sensing organs in the inner ear may have been the first thing to change--preceding the more dramatic sleeking of body shape. The modified ear threw the animals off balance on land, they argue, and set their fate as creatures of the sea.
Cetaceans--the group that includes dolphins and whales--evolved from a hippopotamus-like ancestor (ScienceNOW, 19 September 2001). These creatures bore little resemblance to modern cetaceans, and paleontologists have little idea what drove them into the sea and transformed them into obligate swimmers. The new study suggests the answer may lie deep in the inner ear.
The inner ear contains three fluid-filled tubes called semicircular canals that detect head and body movements. These structures are about three times smaller in cetaceans than in similarly sized land mammals. Previous studies with land mammals suggested that larger semicircular canals might be a feature of animals that are especially agile on land. Intrigued, paleobiologist Fred Spoor of University College London and colleagues used x-ray tomography to reconstruct the inner ears in the skulls of four early cetaceans.
Only 5 million years after the origin of the first whalelike creature, the semicircular canals had shrunk to the exceptionally small size found in modern cetaceans, the team reports in the 9 May issue of Nature. That's about 10 million years before early cetaceans evolved fluke tails, short necks, and fins. The team argues that smaller semicircular canals would diminish the sense of balance, and the creatures would have had a harder time evading predators on land. They speculate that the change might have been an advantage in the sea--allowing the animals to execute acrobatic flips and turns without getting dizzy.
Zhe-Xi Luo, paleontologist at the Carnegie Museum of Natural History in Pittsburgh, is fascinated that the balance organ of early cetaceans adapted to life in the sea before the skeleton changed. "It is a great surprise that they still have their limbs capable of crawling or running, but lost their sensory system to be active on land."