Discover, January 1, 1997

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Discover, December 1, 1996

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From Darwin’s time to today, one group of fossils–those of the early Cambrian Period, beginning 540 million years ago–have baffled researchers. Before the Cambrian, fossils tell us, there existed only a few types of simple, blobby animals. Then, within just 10 million years, almost every major group, or phylum, of animals appeared. Almost all the major body plans seem to have sprung into existence–including phyla such as arthropods (which came to include insects and crustaceans), annelids (leeches and worms), mollusks (squid and clams), echinoderms (starfish and sea urchins), and chordates (fish and humans). Now dubbed the Cambrian explosion, it’s looked upon as the great event in animal evolution–and, in its suddenness, one of evolution’s greatest mysteries.

Continue reading “An Explosion Defused?” →

Discover, November 1, 1996

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Once it seemed that the ocean floor was a desert of darkness. As everyone knew, sunlight was what made life possible by fueling photosynthesis, and sunlight can penetrate only the first few hundred yards of the ocean’s great depths. Lower, a few creatures might still eke out a living by scrounging the organic detritus that drifts down from the surface of the sea. But thousands of feet down, in the utter blackness at the ocean’s bottom, there could be practically nothing.

Continue reading “The Light at the Bottom of the Sea” →

Discover, October 1, 1996

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Is natural selection the prime mover behind evolution? Darwin’s great insight into the mechanics of evolution was that a population of creatures always has a lot of variation–more feathers here, less fat there, more urge to kill there–and some of these variations allow the individuals bearing them to thrive and have more offspring than others. After many generations these traits become more common among the population as a whole. If one imagines fitness as a beckoning peak on a given ecological landscape, then natural selection should be a process that moves species steadily uphill.

Continue reading “Natural Detours” →

Discover, August 31, 1996

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Jeffrey Bada’s lab are nondescript but far from ordinary. They come from a crater near Sudbury, Ontario, that formed 1.85 billion years ago, when a meteorite the size of Mount Everest slammed into Earth. Canadian geologists sent the rocks to Bada, a geochemist at the Scripps Institution of Oceanography, to see if they contained any organic carbon molecules. Not likely, Bada thought: if the molecules hadn’t been incinerated on impact, they would have been destroyed–probably by hungry microbes–long ago. Bada put the rocks on a shelf for a few years.

Continue reading “Buckyballs from space” →