scrubbing your hands outside a livestock tent, stop for a minute and look around. Consider the chickens on display, showing off their chandeliers of feathers. Observe the rabbits burdened with ears too big to lift, the enormous pigs obediently following humans on leashes. Think of their less ridiculous cousins: the jungle fowl, the jackrabbit, the wild boar. These animals demonstrate that there are no fixed essences in life. One of the most important rules of life is that it changes. Boars become pigs, and harmless
E. coli
become killers. It just so happens that
E. coli
is one of the best guides to how life evolves—over days, decades, and billions of years. It vindicates Charles Darwin’s central insights, yet it also reveals how much more bizarre and more fascinating evolution can be than Darwin ever anticipated.
Five
EVERFLUX
THAWING OUT THE ANCESTORS
IN A CORNER OF A LABORATORY at Michigan State University, a table rocks in a precise circle. On top of the orbital shaker are a dozen flasks filled with broth. The liquid swirls without ever breaking a ripple. Each flask contains millions of
E. coli.
They are tended by a biologist named Richard Lenski and his team of technicians and students. Lenski’s experiment looks like countless other experiments that are taking place around the world, but there is one important difference. A typical experiment with
E. coli
may last only a few hours. A team of scientists might use that time to run the bacteria through a maze or rear them without oxygen to see which genes they switch on and off. Once the scientists get enough data to see a pattern, they write up the results and dump the bacteria. But the experiment in Richard Lenski’s lab began in 1988, and forty thousand generations later it’s still going.
Lenski launched the experiment with a single
E. coli.
He placed it on a sterile petri dish and let it divide into identical clones. These clones then became the founders of twelve separate—but genetically identical—lines. Lenski put each line into its own small flask. Instead of the endless feast of sugar that
E. coli
normally enjoys in laboratories, Lenski put his microbes on starvation rations. The bacteria ran out of their glucose by the afternoon. The following morning, Lenski transferred 1 percent of the surviving
E. coli
to a new flask with a fresh supply of sugar.
Periodically Lenski and his students drew some bacteria from each flask and stored them in a freezer. The bacteria’s descendants went on multiplying daily. From time to time, Lenski has thawed out some of the early ancestors. He allows them to recover from their freeze, start eating again, and begin reproducing. And then he has compared them with their descendants. In the process, Lenski has discovered something significant: the bacteria are not what they once were. They are twice as big as their ancestors. They reproduce 70 percent faster. They’ve also become picky about the food they eat. If they’re fed any sugar other than glucose, they grow more slowly than their ancestors. And some of them now mutate at a far higher rate than before. The descendants, in other words, have evolved into something measurably different from their ancestors.
In
The Origin of Species,
Charles Darwin wrote that “natural selection will always act with extreme slowness, I fully admit.” With
E. coli,
Lenski has done something Darwin never dared dream of: he has observed evolution in his own time.
LAMARCK ON THE BEACH
I live close to the Long Island Sound, and from time to time my wife and I take our girls down to the water. The girls throw rocks and gather seaweed. On some days we are joined by nervous sandpipers. They skitter across the beach, stopping to jab their beaks into the mud before skittering off again on their pencil legs.
Two centuries ago, on a beach on the other side of the Atlantic, a French naturalist watched wading birds as well, and he wondered how they had come to be.
E. coli
become killers. It just so happens that
E. coli
is one of the best guides to how life evolves—over days, decades, and billions of years. It vindicates Charles Darwin’s central insights, yet it also reveals how much more bizarre and more fascinating evolution can be than Darwin ever anticipated.
Five
EVERFLUX
THAWING OUT THE ANCESTORS
IN A CORNER OF A LABORATORY at Michigan State University, a table rocks in a precise circle. On top of the orbital shaker are a dozen flasks filled with broth. The liquid swirls without ever breaking a ripple. Each flask contains millions of
E. coli.
They are tended by a biologist named Richard Lenski and his team of technicians and students. Lenski’s experiment looks like countless other experiments that are taking place around the world, but there is one important difference. A typical experiment with
E. coli
may last only a few hours. A team of scientists might use that time to run the bacteria through a maze or rear them without oxygen to see which genes they switch on and off. Once the scientists get enough data to see a pattern, they write up the results and dump the bacteria. But the experiment in Richard Lenski’s lab began in 1988, and forty thousand generations later it’s still going.
Lenski launched the experiment with a single
E. coli.
He placed it on a sterile petri dish and let it divide into identical clones. These clones then became the founders of twelve separate—but genetically identical—lines. Lenski put each line into its own small flask. Instead of the endless feast of sugar that
E. coli
normally enjoys in laboratories, Lenski put his microbes on starvation rations. The bacteria ran out of their glucose by the afternoon. The following morning, Lenski transferred 1 percent of the surviving
E. coli
to a new flask with a fresh supply of sugar.
Periodically Lenski and his students drew some bacteria from each flask and stored them in a freezer. The bacteria’s descendants went on multiplying daily. From time to time, Lenski has thawed out some of the early ancestors. He allows them to recover from their freeze, start eating again, and begin reproducing. And then he has compared them with their descendants. In the process, Lenski has discovered something significant: the bacteria are not what they once were. They are twice as big as their ancestors. They reproduce 70 percent faster. They’ve also become picky about the food they eat. If they’re fed any sugar other than glucose, they grow more slowly than their ancestors. And some of them now mutate at a far higher rate than before. The descendants, in other words, have evolved into something measurably different from their ancestors.
In
The Origin of Species,
Charles Darwin wrote that “natural selection will always act with extreme slowness, I fully admit.” With
E. coli,
Lenski has done something Darwin never dared dream of: he has observed evolution in his own time.
LAMARCK ON THE BEACH
I live close to the Long Island Sound, and from time to time my wife and I take our girls down to the water. The girls throw rocks and gather seaweed. On some days we are joined by nervous sandpipers. They skitter across the beach, stopping to jab their beaks into the mud before skittering off again on their pencil legs.
Two centuries ago, on a beach on the other side of the Atlantic, a French naturalist watched wading birds as well, and he wondered how they had come to be.
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