Discover, June 30, 1995

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For more than 150 million years, until the Cretaceous Period ended 65 million years ago, the skies of Earth were filled with flying reptiles known as pterosaurs. Yet even more than dinosaurs, their land-bound contemporaries, pterosaurs remain a mystery. Two centuries after the first pterosaur fossil was unearthed, paleontologists are still debating whether these strange beasts were more like birds, flying with slim wings and walking on the ground on two legs, or like bats, with loose, membranous wings’ that stretched from wrist to ankle and forced them to crawl on all fours when they weren’t aloft.

Continue reading “A reptile rookery” →

Discover, June 1, 1995

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When you consider the years paleontologists often spend in daily and intimate contact with their fossils, it’s not very surprising that they come to regard their long-gone animals as pets. Some work on the show dogs of the fossil world; they brag about how fast their velociraptor ran or how efficiently their saber-toothed tiger could sever a spinal cord. But when you listen to Jenny Clack talk about her pet, a fossil creature named Acanthostega that she has been working on for seven years, she sounds like the owner of a sweet, homely mongrel. It wasn’t very smart, she says. It probably spent a lot of its time sitting at the bottom of lagoons, hidden in the muck, waiting for something to come by it could eat.

Continue reading “Coming Onto the Land” →

Discover, March 1, 1995

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These are proud times for atmospheric chemists. This year is the last year that American industry will produce chlorofluorocarbons, the ozone-destroying compounds used in such things as refrigerators and insulation. The 130-nation agreement that led to the banning of CFCs, an extension of the Montreal Protocol of 1987, was triggered by the persuasive research of atmospheric chemists. Over the past few years CFC production has already withered drastically, so 1995 may also be the first year in decades that levels of atmospheric chlorine–the ingredient in CFCs that actually destroys the ozone–fall rather than rise.

Continue reading “Unintended Consequences” →

Discover, February 28, 1995

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At times the desert can make people seem small and inconsequential and even foolish. Bill Schlesinger feels that way today. With spikes and tape measure, he and co-worker Jane Raikes have staked out some 100 square yards of desert land in the Jornada Basin, 15 miles north of Las Cruces, New Mexico. Their claim includes some low-slung olive-drab creosote bushes, a clump of wispy tan snakeweed, and a lot of bare soil. Some ants roam the ground. A palm-size Texas horned lizard tries to stay cool in the shade of a creosote. It is a patch of desert that looks pretty much like countless other patches of desert in North America.

Continue reading “How to make a desert” →

Discover, February 1, 1995

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Before 1977 life came in two fundamental flavors: bacteria and the rest of us. The bacteria, also known as prokaryotes, had DNA that floated free in the cell, whereas the eukaryotes–such as fungi, plants, and animals–had their DNA balled up in a nucleus. But in 1977 Carl Woese, a microbiologist at the University of Illinois, showed that there was actually a third type of life, a group of prokaryotes he called the archaea. Not only are the archaea genetically distinct from the other prokaryotes–which Woese renamed eubacteria, or true bacteria–they are more closely related to us than they are to Escherichia coli.

Continue reading “Triumph of the Archaea” →