Discover, June 1, 1998

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There are two basic points of view on global warming: it’s a problem or it’s not. In most of the world that argument is over and the pessimists have won, but not in the United States. And yet politically, if not scientifically, the argument seemed to be settled long ago—on October 15, 1992, to be precise, when the United States became the fourth country, after Mauritius, the Seychelles, and the Marshall Islands, to ratify the United Nations Framework Convention on Climate Change. George Bush had signed the treaty at Rio de Janeiro four months earlier. It committed us to an objective: Stabilization of greenhouse gas concentrations in the atmosphere at a level that would prevent dangerous anthropogenic interference with the climate system.

Continue reading “Carbon Cuts and Techno-Fixes” →

Discover, June 1, 1998

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For 139 years, ever since its delicate bones and feathers were found splayed on a limestone slab in a German quarry, Archaeopteryx has had the distinction of being the most primitive bird known. Its clawed wings, toothy beak, and long bony tail, most paleontologists now believe, show the transformation of a lineage of bipedal dinosaurs into birds. Since its discovery, the 145-million-year-old Archaeopteryx has perched alone on a low branch of the avian evolutionary tree. Now the old bird finally has company. In March, paleontologists described a 65- to 70-million-year-old bird from Madagascar, which, though younger than Archaeopteryx, is almost as primitive. In life it would have resembled a little winged Velociraptor.

Continue reading “Evolution Watch: A Sickle in the Clouds” →

Discover, April 30, 1998

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The evolution of ocean-dwelling whales from terrestrial mammals was one of the most dramatic transitions in the history of vertebrates. To go from the land back into the water left behind so many millions of years earlier called for a monstrously great change, a drastic reworking of physical form and function. It took some 10 million years to accomplish-roughly, the period from 50 million to 40 million years ago. Yet it’s only in the last few years that we’ve come to grasp the essential facts of the story. Fossils of primitive whales had been known since the early nineteenth century, but the pioneering paleontologists of the time, not surprisingly, simply could not make sense of them-it would be decades before Darwin provided the evolutionary model that made the origin of whales understandable.

Continue reading “The equation of a whale” →

Discover, February 1, 1998

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Just north of the town of Gallup, New Mexico, is a hill of olive-colored sandstone. One late spring afternoon paleontologist Stephen Hasiotis walks up its grassy apron, crosses over onto bare rock, and loses his composure. Oh man, oh man, he mutters. Look at all this.

He kneels by a stub of white rock—one of many—that just barely pushes through the darker stone around it. Its surface is not the smooth, featureless face you’d expect from an exposure to wind and rain; rather it shows a mass of fine tangles, of tubes branching into more tubes or tying themselves off in blobs.

Continue reading “A Secret History of Life on Land” →

Discover, January 1, 1998

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At some point during the growth of an insect larva, a gene called Dll switches on and helps organize some of its cells into legs. If for some reason Dll is shut off, the insect will produce only stumps. In the early 1990s scientists were surprised to discover that almost identical copies of this gene can be found in mammals and other vertebrates—and that they too switch on as legs form. This was surprising for two reasons. For one thing, insects and vertebrates have radically different limbs: ours have bone inside and muscle outside, while bugs are the reverse—their flesh is protected by an armored exoskeleton.

Continue reading “The Year in Science: Evolution 1997” →