Discover, April 30, 1998

Link

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

Link

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

Link

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” →

Discover, January 1, 1998

Link

In the far northern reaches of the Siberian tundra is an enigmatic place called Popigai. The high cliffs along the rivers there are made of rock that shows signs of once having been completely melted, and satellite images reveal that the tundra actually forms a giant ring-shaped depression 60 miles across—which suggests that Popigai is a vast meteorite crater. Last July a team of Canadian and Russian scientists announced that they had determined when the meteorite hit: 35.7 million years ago, give or take 200,000 years. They calculated that date from the amount of radioactive argon that had decayed in the rocks since they resolidified after the impact.

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

Discover, January 1, 1998

Link

Treating wastewater is expensive: to get rid of organic matter, phosphates, and nitrogen compounds that farms and cities release into rivers, you need to pump the water through costly complexes of pumps, filters, and tanks. A tidal marsh, on the other hand, does the same job free of charge. The polluted water fertilizes plants and microbes, which in turn support a huge food web, and by the time the water makes its way out of the marsh, it’s scrubbed clean. One acre of tidal marsh performs about $2,800 worth of water purification every year. Multiply that by the 165 million acres of coastal wetlands on the planet, and you get a tidy annual bill of $462 billion.

Continue reading “The value of the free lunch” →