By Carl Zimmer

The New York Times, May 6, 2008
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“Why are humans so smart?” is a question that fascinates scientists. Tadeusz Kawecki, an evolutionary biologist at the University of Fribourg, likes to turn around the question.

“If it’s so great to be smart,” Dr. Kawecki asks, “why have most animals remained dumb?”

By Carl Zimmer

The Boston Globe April 28, 2008
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Casey Dunn has gathered his share of weird animals. He dredged up sea spiders that live around the docks in Waikiki. He dived to the sea floor to scoop up mud, in search of bizarre, spiny creatures called kinorhynchs that are smaller than a grain of sand.

Dunn, a biologist at Brown University, hunts for weird animals to get his hands on their DNA. Hidden in their genes is a record of the history of the entire animal kingdom, some 700 million years of evolutionary change.

By Carl Zimmer

The New York Times, April 22, 2008
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Adapted from Carl Zimmer’s book Microcosm: E. coli and the New Science of Life

We humans differ from one another in too many ways to count. We are shy and bold, freckled and pale, truckers and hairdressers, Buddhists and Presbyterians. We get cancers in the third grade and live for a century. We have fingerprints.

Scientists have only a rough understanding of how this diversity arises. Some of it stems from the different experiences we have, from our time in the womb on through childhood and into our mature years. These molding influences include things like the books we read and the air we breathe. Our diversity also stems from our genes--the millions of typographical differences between one genome and another.

We put a far bigger premium on nature than nurture when it comes to our individuality. That’s one reason why reproductive cloning inspires so much horror. If genes equal identity, then a person carrying someone else’s DNA has no distinct self.

But there’s a deep flaw in this way of thinking, one that blinds us to how biology--human or otherwise--really works. A good counterexample is E. coli, a species of bacteria that lives harmlessly in every person’s gut by the billions. A typical E. coli contains about 4,000 genes (we have about 20,000). Feeding on sugar, the microbe grows till it is ready to split in two. It makes two copies of its genome, almost always managing to produce perfect copies of the original. The single microbe splits in two, and each new E. coli receives one of the identical genomes. These two bacteria are, in other words, clones.

Surely, then, E. coli must be all nature and no nurture. A colony descended from a single E. coli ancestor is just a billion identical cousins, all responding to the world with the same set of genes.

Yet as plausible as this sounds, it’s far from the truth. A colony of genetically identical E. coli is, in fact, a mob of individuals. Under identical conditions, they will behave in different ways. They have fingerprints of their own.

By Carl Zimmer

Wired.com Dissection column, April 18, 2008
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In life, one mystery gives way, revealing a new one underneath, waiting to be solved.

An early mystery was genes. Scientists did not know what hidden factor lurked inside living things, giving rise to their traits and traveling from parent to child to recreate those traits anew.

The answer, of course, turned out to be DNA: Segments of the molecule encode the proteins and RNA molecules that carry out the work of life, send signals, capture energy and build biomass.

But it quickly became clear that just having genes was not the full secret of life. The genes need to become active at the right time and place. Think about it: Each one of your cells contains genes that can produce hair and toenails, and can crank out neurotransmitters and digestive enzymes. If all your genes did churn away, your body would become a hideous, useless jumble. Our life depends on the courteous restraint of our genes.

By Carl Zimmer

Wired.com Dissection column, April 4, 2008
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It’s easy to be over-dazzled by the brain. Who could be unimpressed by the billions of neurons packed into our skulls, linked together by trillions of connections, capable of encoding memories from decades ago, of playing a saxophone, of sending space probes out of our solar system? We naturally want to know how our brain got to be so good. But there’s an even more interesting question worth asking: How do we manage to survive with a brain that’s so bad?

By Carl Zimmer

Wired.com Dissection column, March 21, 2008
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We like to tell ourselves that it's easy to distinguish between the natural and the artificial, but they have a knack for fooling us. When European colonists traveled through the patchwork of forests and meadows of New England, they thought they were exploring primeval nature. In fact, Native Americans had been tending it carefully with fires for centuries. When the Viking probe snapped a fuzzy picture of a mountain on Mars in 1976, some people were sure it showed a giant face carved by Martians. When another probe took a sharper picture in 2001, all trace of the face had vanished.

Today the mystery of the natural versus the artificial is moving from mountains and forests down to the microscopic realm. Scientists can now synthesize DNA from scratch. They regularly add new genes to bacteria, plants and animals. They are learning how to manufacture whole genomes. Can we tell the difference between our growing menageries of engineered organisms and natural ones? A fascinating new study from scientists at Lawrence Livermore National Lab in California shows that we can -- at least for now.

By Carl Zimmer

Slate, March 19, 2008
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Listen to my article on Slate's podcast (mp3 file here)



An outbreak of E. coli isn't usually the stuff of feel-good stories. Feel-bad is more like it--or even feel-organ-failure. But recent E. coli outbreaks can offer us a bit of solace. We live in the anxious age of synthetic biology, when scientists can reconstruct entire genomes from raw chemicals, and when we all fret that someone is going to use this new technology to create a monster bug and unleash a man-made plague. According to one government report, "The effects of some of these engineered biological agents could be worse than any disease known to man." But a close look at recent outbreaks of E. coli--and a closer look at the bacteria themselves--may help us to put aside our fears for the moment. Engineering plagues is harder than it looks.

By Carl Zimmer

Dissection column, Wired.com, March 6, 2008
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The Grand Canyon is a victim of terrible press.

Its banded walls make up one of the most magnificent landscapes on Earth. And yet it seems the only time reporters bother to mention its geology is when they are writing about creationists and their bogus claims that the Grand Canyon formed a few thousand years ago. It's a shame, because the real story of the Grand Canyon is a riveting epic. Even its scientific history is fascinating: Figuring out just how old the Grand Canyon is has challenged geologists for 150 years. And just this week, the mystery may be solved.

By Carl Zimmer

The New York Times, March 4, 2008
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For the past two decades, Kay E. Holekamp has been chronicling the lives of spotted hyenas on the savannas of southern Kenya. She has watched cubs emerge from their dens and take their place in the hyena hierarchy; she has seen alliances form and collapse. She has observed clan wars, in which dozens of hyenas have joined together to defend their hunting grounds against invaders.

“It’s like following a soap opera,” said Dr. Holekamp, a professor at Michigan State University.

Throughout her career, Dr. Holekamp has remained vigilant against anthropocentrism. She does not think of the hyenas as long-eared people running around on all fours. But the lives of spotted hyenas, she has concluded, share some profound similarities with our own. In both species, a complex social world has driven the evolution of a big, complex brain.

By Carl Zimmer

The New York Times, February 26, 2008

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Imagine the Book of All Species: a single volume made up of one-page descriptions of every species known to science. On one page is the blue-footed booby. On another, the Douglas fir. Another, the oyster mushroom. If you owned the Book of All Species, you would need quite a bookshelf to hold it. Just to cover the 1.8 million known species, the book would have to be more than 300 feet long. And you’d have to be ready to expand the bookshelf strikingly, because scientists estimate there are 10 times more species waiting to be discovered.

It sounds surreal, and yet scientists are writing the Book of All Species. Or to be more precise, they are building a Web site called the Encyclopedia of Life (www.eol.org). On Thursday its authors, an international team of scientists, will introduce the first 30,000 pages, and within a decade, they predict, they will have the other 1.77 million.

By Carl Zimmer

“Dissection” column, Wired.com, 2/22/08

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Everyone likes a medical mystery -- even more so when the mystery in question is solved. When a few people in Queens developed fevers in 1999, scientists pinpointed an American strain of West Nile virus. When people in East Asia began to get particularly wicked coughs in 2003, scientists discovered an entirely new virus called SARS. As much as we admire the ingenuity that went into solving these medical enigmas, that doesn't mean we should ignore the medical-sleuthing stories that haven't yet reached a satisfying ending. Their very mystery actually says something important about how nature works.

By Carl Zimmer

The New York Times, February 19, 2008

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WOODS HOLE, Mass. --The cuttlefish in Roger Hanlon’s laboratory were in fine form. Their skin was taking on new colors and patterns faster than the digital signs in Times Square.

By Carl Zimmer

“Dissection” column, Wired.com, 2/8/08
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Modern life means small families. Starting about two centuries ago, families in Western Europe began to shrink, and then -- country by country, continent by continent -- the rest of the world followed suit. The trend is so big that it may rein in the world population's exponential growth, perhaps even causing it to stop growing altogether over the next century.

But exactly why families are shrinking is a mystery. Rising living standards seem to have something to do with it. It's certainly true that as living standards rose in England -- as children died less from diseases, as the country overall became richer -- the size of the English family shrank. When other countries became wealthier, their families shrank, too. These days, affluent countries tend as a rule to have smaller families than poor ones.

By Carl Zimmer

Dissection: Commentary at Wired.com, January 25, 2008
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Yesterday the news broke, and it broke big: genome pioneer Craig Venter and his team of scientists at his eponymous institute had created a microbe’s genome from scratch. Massive stories ran in newspapers and magazines, tingling with the sense that we were on the edge of a revolution. Time’s piece was accompanied by a foreboding picture of Venter in a forest, wearing a dark coat and scarf, his beard giving his scowl a particularly dire look. The picture matched the story’s ominous mood: “He has gone beyond merely sequencing a genome and has designed and built one. In other words, he may have created life,” the article intoned. The Economist promised that when Venter is done, he will “have erased one of the last mythic distinctions in science--that between living and non-living matter.”

I get the impression I am supposed to be tingling, my heart racing with exaltation or terror or...something. And yet I feel like I have a lesion in my amygdala, unable to respond to the threat of an electric shock. In some ways, this is actually old news. And in other ways, it’s news that hasn’t yet been written, and won’t be for decades.

By Carl Zimmer

Science, January 18, 2008
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In 1494, King Charles VIII of France invaded Italy. Within months, his army collapsed and fled. It was routed not by the Italian army but by a microbe. A mysterious new disease spread through sex killed many of Charles's soldiers and left survivors weak and disfigured. French soldiers spread the disease across much of Europe, and then it moved into Africa and Asia. Many called it the French disease. The French called it the Italian disease. Arabs called it the Christian disease. Today, it is called syphilis.

The sensational debut of syphilis inspired centuries of debate. Some have argued that Columbus's crew brought the disease from the New World to Europe; others say the disease existed unrecognized for centuries in the Old World before turning virulent. This week in the journal PLoS Neglected Tropical Diseases, a team of researchers argues that neither hypothesis is correct. Syphilis originated as a milder, nonsexual disease in the New World, they say, and it evolved into its current form after Europeans arrived. Among the evidence they offer is a mysterious disease restricted to an isolated tribe in a South American jungle. Its DNA, they argue, reveals that it is a kind of protosyphilis.

By Carl Zimmer

Nature, January 17, 2008
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A review of Your Inner Fish: A Journey into the 3.5-Billion-Year History of the Human Body by Neil Shubin

Six hundred years ago, anatomists were rock stars. Their lessons filled open-air amphitheatres, where the curious public rubbed shoulders with medical students. While a surgeon sliced open a cadaver, the anatomist, seated above on a lofty chair, deciphered the exposed mysteries of the bones, muscles and organs.

Modern anatomists have retreated from the stage to windowless medical-school labs. They have ceded their public role to geneticists unveiling secrets encrypted in our DNA. Yet anatomists may be poised for a comeback, judging from Your Inner Fish. Neil Shubin, a biologist and palaeontologist at the University of Chicago, Illinois, delves into human gristle, interpreting the scars of billions of years of evolution that we carry inside our bodies.

By Carl Zimmer

Time, January 17, 2008

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There's nothing like being in love. Minutes seem to creep and fly at the same time. We get lost on the way home, thinking of the next date. Music cries out to us alone, and the full moon winks our way. Long after other memories fade, the recollection of love lingers. It's pure magic. Or at least that's what we like to tell ourselves.

By Carl Zimmer

Il Sole 24 (Italy), January 13, 2008


Last fall, the organizers of the Rome Science Festival asked me to come give a lecture about mass extinctions--about how our planet has experienced huge die-offs in the past, and whether it may be on the verge of another die-off today. Only after I began to prepare my talk did I realize how fitting it was to speak of such matters in Italy. For it is in Italy that some of the most important advances in understanding extinctions have taken place.

By Carl Zimmer

The New York Times, January 1, 2008

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A review of No Way Home: The Decline of the World's Great Animal Migrations, by David S. Wilcove.


The world is etched with invisible paths, the routes taken each year by uncountable swarms of geese, elk and salmon, of dragonflies, zebras and leatherback turtles.

Their migrations speak to us in some unfathomably deep way. Birders flock to stopover sites like Cape May, N.J., to watch birds on their journeys to the far north in the spring and back to the tropics in the fall. Eco-tourists head for the Serengeti to train binoculars on herds of wildebeest that stretch to the horizon. American schoolchildren watch monarch butterflies hatch from chrysalises in their classrooms and then see them off on their trip to Mexico.

But in his new book “No Way Home,” David Wilcove, a Princeton biologist, warns that “the phenomenon of migration is disappearing around the world.”