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5 December 2013 11:26 am ,
Vol. 342 ,
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,...
Since arriving on the island of Guam in the 1940s, the brown tree snake ( Boiga irregularis ) has extirpated native...
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...
- 5 December 2013 11:26 am , Vol. 342 , #6163
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Life Breathed Into Deep-Sea Evolution
4 August 1998 7:30 pm
The best spot for evolving radically new marine creatures has seemed to be in shallow waters, where storms and fierce battles for resources wipe out the competition. Now two researchers say in today's Proceedings of the National Academy of Sciences that the deep sea can also give birth to new life forms--if it contains enough life-sustaining oxygen.
Previous studies of the fossil record have suggested a straightforward picture of how new types of marine invertebrates evolved: New creatures first appeared in shallow water, diversified in deeper water, and then moved to deep-sea environments. The most usual explanation is that hurricanes and other stressful conditions near the shore caused the extinction of some animals--and so cleared the way for new groups to evolve in the absence of competition.
But the previous analyses of this pattern may have failed to take into account a simple biological fact: Most marine organisms can't live in oxygen-poor water. Since the deep-sea bottom has frequently been plagued by a low levels of oxygen, two paleontologists--David Jacobs of the University of California, Los Angeles, and David Lindberg of the University of California, Berkeley--took a closer look at the fossil data. They found that novel groups did originate onshore through much of the Mesozoic Era, 245 to 90 million years ago, when the deep sea was frequently oxygen-poor. But after that, new orders of marine invertebrates were just as likely to originate in deep water as shallow. They attribute this change to the cooling of polar regions, which pumped the deep sea with dense, oxygen-rich water.
Other experts are pleased with the suggestion that oxygen levels rather than location spur evolutionary novelty. "There's been this notion in the past that there's some fundamental reason why [orders of invertebrates] should appear nearshore, and I've never been satisfied with this explanation," says paleontologist Steven Stanley of Johns Hopkins University.