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Organic Lake, Antarctica, is home to myriad species that thrive at temperatures below freezing.

Comfortable in the Cold: Life Below Freezing in an Antarctic Lake

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<p>
 A big part of Ricardo Cavicchioli’s job as a biologist is finding new species. And Cavicchioli, a professor at the University of New South Wales in Australia, has had particular good fortune at a place called Organic Lake, in the Vestfold Hills. “We discovered things we were never even looking for,” Cavicchioli says.
</p>
<p>
 If you actually tagged along with Cavicchioli on one of his trips to Organic Lake, however, you might be deeply skeptical that this was a place where anything could live. The Vestfold Hills are not a rolling tropical landscape. They are located in East Antarctica. Organic Lake gets as cold as -13˚ C. The only reason its depths don’t turn to ice is thanks to its staggering concentration of salt.
</p>
<figure class="richtext-image full-width">
<img alt="Ricardo Cavicchioli" class="richtext-image full-width" src="https://staging.pbs.org/wgbh/nova/media/images/dscf3541.width-990_5wwlNzO.jpg"/>
<figcaption>Ricardo Cavicchioli collects samples at Organic Lake in Antartica's Vestfold Hills.
        
    </figcaption>
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 Despite these unbearably cold conditions,
 <a href="http://maps.google.com/maps?q=loc:-68.456389,78.189861&amp;hl=en&amp;ll=-68.457844,78.185234&amp;spn=0.037441,0.077162&amp;t=h&amp;z=14">
  Organic Lake
 </a>
 is home to all manner of microbial life, from algae to bacteria to viruses. It even has viruses that infect other viruses. Though life in Organic Lake is in many ways the same as elsewhere on Earth, it is also profoundly different in some ways. If Cavicchioli—a warm-blooded mammal—were to fall into the lake, he might die of hypothermia in a matter of minutes. But for the species in Organic Lake, frigid temperatures are comfortable. Warm them up to room temperature, and many would die in the scorching heat.
</p>
<h2>
 Redefining Typical Temperature
</h2>
<p>
 Cavicchioli is among a growing group of scientists who are dedicating their careers to studying one of the least understood, yet profoundly important forms of life: organisms that thrive in the cold, or psychrophiles, also known as cryophiles. Traditionally, biologists have neglected chilly places, which, in hindsight, has been a huge oversight. Over 80 percent of the planet never gets above 5˚ C. “It’s the norm, not the extreme,” Cavicchioli says.
</p>
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<p>
 Neglect of the cold biosphere is understandable when you consider the tools that biologists used to look for life.
</p>
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<p>
 The “cold biosphere,” as Cavicchioli calls it, contains organisms with remarkable adaptations to let them grow at low temperatures. Scientists are seeking now to understand psychrophiles not just for their own sake, but for the lessons they can offer. Astrobiologists know that the most promising places for extraterrestrial life in the Solar System are also bitterly cold. If aliens exist, in other words, they are probably a lot more like the life in Organic Lake than in Pennsylvania. Meanwhile, biochemists are intrigued by the strange workings of cold-adapted proteins for an entirely different reason—they hope to adopt them for use in biotechnology, so that we can harness the power of the cold biosphere in our lukewarm lives.
</p>
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<p>
 The traditional neglect of the cold biosphere is understandable when you consider the tools that biologists used to look for life. For a long time, the only way they could study microbes was to take a sample from a place—say, the water of Organic Lake—and then try to grow the organisms in their lab.
</p>
<p>
 This method works well for species that enjoy the same conditions we humans like. That’s why
 <i>
  E. coli
 </i>
 , which flourishes in warm temperatures and high levels of oxygen, became the favorite organism of thousands of scientists. But this method misses all the microbes that don’t thrive in those conditions.
</p>
<p>
 In the early 2000s, Cavicchioli was among the first scientists to bring a new tool to the cold biosphere. Instead of trying to rear psychrophiles in the lab, they fished for their DNA. By sequencing stretches of DNA in water samples, the scientists could identify new species and find their closest relatives. This gene-based hunt is yielding a vast diversity of living things in even the most forbidding places, including and beyond Organic Lake. On mountaintops and chilly sea floors, in caves and polar caps, biologists would find bacteria, archaea, fungi, algae, and viruses. Some of these organisms got blown or washed away from warmer places and had become dormant. But many of them were alive—feeding, growing, and reproducing.
</p>
<h2>
 Cut Out for the Cold
</h2>
<p>
 As scientists examine the genes of these hidden psychrophiles, they’re also learning more about how these organisms manage to survive in places that would be fatally frigid for others. If you cool our cells down, for example, their membranes get rigid. Psychrophiles keep their membranes more pliable by adjusting the fatty acids that make them up. They use more polyunsaturated fats in their membranes than organisms at higher temperatures. To appreciate the difference, consider how much easier it is to spread cold margarine (which has lots of polyunsaturated fats) than it is to spread cold butter (which doesn’t).
</p>
<p>
 Inside our cells, the cold also wreaks havoc on proteins. Proteins carry out thousands of different kinds of chemical reactions, such as cutting apart molecules, joining together others, and moving other molecules in and out of cells. It takes energy for them to do these jobs. They get a lot of that energy from our body heat, which keeps them continually jiggling. A little burst of extra energy (from a molecule called ATP) is all it takes to launch them into action.
</p>
<p>
 As the temperature drops, proteins get sluggish. A burst of ATP may not be strong enough to activate them. If you take a protein from our warm bodies and chill it down to the freezing point of water, its activity may drop by eighty-fold. Proteins also risk folding down into a deformed clump as they get cold, with the result that they react with other molecules in the wrong way, causing trouble inside the cell.
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<img alt="" class="richtext-image full-width" src="https://staging.pbs.org/wgbh/nova/media/images/phycodnavirus.width-990_pXM4K4G.jpg"/>
<figcaption>A phycodnavirus found in Organic Lake
        
    </figcaption>
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<p>
 Yet the proteins in psychrophiles manage to work just fine even below the freezing point. Some of their success is due to so-called “cold-shock proteins,” which unfold DNA from their tangles and restore them to their proper shape. We humans and other warm-blooded organisms make cold-shock proteins when our cells sense that the temperature has dropped. Psychrophiles, by contrast, can keep a steady supply of them on hand at all times.
</p>
<p>
 Psychrophile proteins also avoid biochemical torpor by being much more flexible than typical proteins in warmer organisms. Even a little heat is enough to make them jitter. They’re so floppy, in fact, that warming them up to body temperature can tear them apart.
</p>
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<p>
 Strategies like these let psychrophiles survive where we would freeze to death. So far, the current record-holder for surviving in the cold is a microbe called
 <i>
  Planococcus halocryophilus.
 </i>
 Scientists from McGill University discovered it in the permafrost of northern Canada, and recently they demonstrated that it can grow at -15˚ C and stay metabolically active at -25˚ C.
</p>
<p>
 But the adaptations that allow psychrophiles to endure in these extreme habitats don’t exactly leave them breeding like rabbits. In many cold ecosystems, life unfolds in awesomely slow motion. In Deep Lake, a lake near Organic Lake that is even saltier and never freezes (even when the air temperature reaches -40˚ C), Cavicchioli studies a species of microbe that divides only six times per year. (
 <i>
  E. coli
 </i>
 , in contrast, needs as little as 20 minutes to divide in the lab.) “This is incredibly slow—they’re basically doing nothing,” Cavicchioli says. Yet these microbes are one of the dominant species in the lake, in part because nothing else grows faster than they do. “From their point of view,” asks Cavicchioli, “who cares?”
</p>
<h2>
 Clues to Life Elsewhere
</h2>
<p>
 The fact that life can endure in a place like Organic Lake and Deep Lake doesn’t just have implications for biology on Earth. It also raises our hopes about the possibility of life elsewhere in the Solar System. When astrobiologists contemplate extraterrestrial life, they first think about water. All life as we know it here on Earth has to have water to survive. But Earth is not the only place in the Solar System with the molecule in abundance. Europa, a moon of Jupiter, may have an ocean of liquid water hidden under a thick sheet of ice. Other moons of Jupiter and Saturn are known to have ice. The white at the North Pole of Mars is an ice cap made of water, too, and there are many clues that Mars was once a watery planet, and vestiges of those ancient seas may still be underground.
</p>
<p>
 Astrobiologists are searching for extraterrestrial life on cold places like Europa, an icy moon of Jupiter. For more on life beyond Earth,
 <a href="http://www.pbs.org/wgbh/nova/space/finding-life-beyond-earth.html">
  watch the complete program
 </a>
 .
</p>
<p>
 But these planets aren’t just wet. They’re also cold—brutally so. The surface of Europa can get down to -223˚ C, for example. On a balmy day, some parts of Mars can get as warm as 20˚ C, but for the most part it’s a far colder place than Earth, getting down to as cold as -140˚ C.
</p>
<p>
 If we only knew about life based on warm-adapted biology, these temperatures might seem like a show-stopper. Life on Europa ought to just grind to a halt. But Earth’s psychrophiles are living proof that organisms can evolve many adaptations for withstanding cold.
</p>
<h2>
 Harnessing the Cold
</h2>
<p>
 Meanwhile, here on Earth, some scientists are interested in psychrophiles for much more practical reasons. We use proteins in our everyday lives for doing everything from baking bread to washing clothes to cleaning up oil spills. We typically use proteins that scientists isolated from organisms that live with us in the warm biosphere. These proteins require a lot of extra heat to work as well as possible.
</p>
<p>
 Millions of years of life in the cold have adapted psychrophile proteins to work with very little heat. That raises the possibility that they could carry out many jobs far more efficiently than current technologies allow. “There’s a huge scope there, and companies are realizing it more and more,” Cavicchioli says.
</p>
<p>
 A few psychrophile proteins have already entered the marketplace. A Belgian company called Puratos sells a cold-adapted protein for bread-baking, for example. It makes dough rise faster by breaking down cell walls quickly. Researchers are looking into detergents for washing machines that will work effectively in even colder water than current “cold-water” formulations. Other possible applications of psychrophile proteins include enzymes for cleaning water filtration systems.
</p>
<p>
 Cavicchioli worries that we may not be able to appreciate the lessons psychrophiles have to offer if we don’t protect fragile places like Organic Lake from the threats they now face—everything from tourism to climate change. Global warming is hitting polar regions the hardest; species adapted to warmer temperatures may outcompete the cold-adapted species there now.
</p>
<p>
 “There’s very good reason to protect as many of these natural environments as we can,” Cavicchioli said.
</p>
<p>
 Photos courtesy Ricardo Cavicchioli
</p>
<p>
 Source:
</p>
<p>
 Cavicchioli, R., Charlton, T., Ertan, H., Omar, S. M., Siddiqui, K. S. and Williams, T. J. 2011. Biotechnological uses of enzymes from psychrophiles.
 <i>
  Microbial Biotechnology
 </i>
 4: 449–460. doi:
 <a href="http://dx.doi.org/10.1111/j.1751-7915.2011.00258.x">
  10.1111/j.1751-7915.2011.00258.x
 </a>
</p>
<p>
<em>
  The article was updated to clarify Organic Lake's low temperature, details on how psychrophile biochemistry works, and where bacteria were found to divide six times per year (Deep Lake, not Organic Lake).
 </em>
</p>

<p>Cold-loving species are changing everything from laundry detergents to our search for extraterrestrial life.</p>

Darwin came up with his theory of sexual selection to explain the peacock's over-the-top tail feathers, among other extravagant physical traits in animals.

Ten Great Advances in Evolution

<p data-block-key="kykoe">Carl Zimmer looks at 10 significant recent advances in evolution studies.</p>

Do Neanderthals belong within Homo sapiens? Paleoanthropologists cannot agree. Here, a skull cast of the La Chapelle-aux-Saints Neanderthal discovered in 1908.

Are Neanderthals Human?

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<p>In August 1856, in the German valley of Neander—<i>Neanderthal</i> in German—men cutting limestone for the Prussian construction industry stumbled upon some bones in a cave. Looking vaguely human, the bones—a piece of a skull, portions of limbs, and fragments of shoulder blades and ribs—eventually made their way to an anatomist in Bonn named Hermann Schaafhausen.</p><p>Schaafhausen pored over the fossils, observing their crests and knobs. He noticed that the bones had the overall shape you'd expect from a human skeleton. But some bones had strange features, too. The skullcap, for example, sported a heavy brow ridge, hanging over the eyes like a boney pair of goggles. It was, at once, human and not.</p><p>The Neanderthal Man challenged Schaafhausen with a simple yet profound question: Was it a human, or did it belong to another species?</p><p>It's been over 150 years since the bones first emerged from the Neander Valley—a time during which we've learned a vast amount about human evolution. Today, scientists can even scan the genomes of Neanderthals who died 50,000 years ago. And yet the debate still rages. It's a debate that extends beyond Neanderthals, forcing us to ask what it means to be a species at all.</p><h3>Variations on a theme</h3><p>The Neander Valley bones were a sensation as soon as Schaafhausen published his report on them in 1857, because nothing like them had been seen before. Earlier in the 1800s, cave explorers had found ancient human bones, sometimes lying next to fossils of cave bears and other extinct animals. Naturalists had a hazy sense from such bones that humanity had been around for quite a long time. But the idea that humans—or any other species—had evolved was scandalous. Darwin would not publish <i>The Origin of Species</i> for another two years. Instead, naturalists saw humans as a species distinct from chimpanzees, gorillas, and all other primate species. We were distinct today, and we had been distinct since creation.</p>
<div class="pullquote">
<p>The youngest Neanderthal fossils date to 28,000 years ago.</p>
</div>
<p>Within the human species, European anatomists divided people into races. They often ranked Europeans as the noblest race, considering the others barely better than apes. To justify this racist view of humanity, anatomists searched for clear-cut differences between the skeletons of different races—the size of skulls, the slopes of brows, the width of noses. Yet their attempts to neatly sort people into groups were bedeviled by the blurry variations in our species. Within a single so-called race, people varied in color, height, and facial features. Schaafhausen knew, for example, about a skull dug up from an ancient grave in Germany that "resembled that of a Negro," as he wrote.</p><p></p>
<figure class="richtext-image full-width">
<img alt="Barbarian fighting Roman soldier" class="richtext-image full-width" src="https://staging.pbs.org/wgbh/nova/media/images/are-neanderthals-human-02.width-990_MvkIn7z.jpg"/>
<figcaption>A barbarian (with sword) attacking a Roman legionary in a second-century relief. Neanderthals wouldn't have been out of place amongst such savage sorts, Schaafhausen believed.
        
        <div class="credit">© The Gallery Collection/Corbis</div>
</figcaption>
</figure>
<h3>European savages</h3><p>On this confusing landscape Schaafhausen tried find a place for the Neanderthal Man. He decided that its heavy brow didn't disqualify it as a human. To back up this diagnosis, he relied on stories of ancient European savagery. "Even of the Germans," Schaafhausen wrote in his 1857 report on the Neander Valley bones, "Caesar remarks that the Roman soldiers were unable to withstand their aspect and the flashing of their eyes, and that a sudden panic seized his army."</p><p>Schaafhausen searched historical records for other clues of Europe's monstrous past. "The Irish were voracious cannibals, and considered it praiseworthy to eat the bodies of their parents," he wrote. In the 1200s, ancient tribes in Scandinavia still lived in the mountains and forests, wearing animal skins, "uttering sounds more like the cries of wild beasts than human speech."</p><p>Surely, in such a savage place, this heavy-browed Neanderthal would have fit right in.</p><h3>A distinctive creature</h3><p>When Schaafhausen published his report, many other naturalists tried to make sense of the bones for themselves. After Darwin published his theory of evolution in 1859, new possibilities arose: Perhaps humans evolved from Neanderthals, or perhaps they were both descended from a common ancestor.</p><p>Thomas Huxley, Darwin's great champion in England, argued that Neanderthals were human, pointing to the thick foreheads of living Australian Aborigines. William King, an Irish geologist, disagreed. In an 1864 paper, "The Reputed Fossil Man of the Neanderthal," he pointed to a long list of traits that separated it from living humans—from its tightly curved ribs to the massive sinuses in its skull. Its braincase was so ape-like that it could not house a human-like brain.</p><p></p>
<figure class="richtext-image full-width">
<img alt="Australian Aborigine" class="richtext-image full-width" src="https://staging.pbs.org/wgbh/nova/media/images/are-neanderthals-human-03.width-990_SqesZNV.jpg"/>
<figcaption>Australian Aborigines have a prominent brow ridge, a fact that helped lead Thomas Huxley to argue that Neanderthals were indeed human.
        
        <div class="credit">© Kerrie Kerr/iStockphoto</div>
</figcaption>
</figure>
<p>"I feel myself constrained to believe that the thoughts and desires which once dwelt within it never soared beyond those of a brute," King wrote.</p><p>From all this evidence, King concluded that the Neanderthal Man was not simply an ancient European, as Schaafhausen had thought. It was a separate species. He even gave that species a name: <i>Homo neanderthalensis.</i></p><h3>Mounting evidence</h3><p>King was certainly right that Neanderthals were distinct from living humans. Subsequent generations of fossil-hunters have found remains of Neanderthals from Spain to Israel to Russia. The youngest Neanderthal fossils date to 28,000 years ago. The oldest ones date back over 200,000 years. Like the original Neanderthal Man, they were stocky, with a heavy brow ridge and other singular traits. We can't know exactly what thoughts and desires soared in their heads, but they certainly left behind some telling clues—carefully engineered spear blades and stone knives; painted shells that might have been used as jewelry. Neanderthals endured the comings and goings of ice ages in Europe and Asia, hunting for reindeer, rhinoceroses, and other big game.</p><p>As the fossils have emerged, paleoanthropologists have revisited the question of whether Neanderthals are part of our own species—call them <i>Homo sapiens neanderthalensis</i>—or a separate <i>Homo neanderthalensis.</i> Some researchers argued that Neanderthals belonged to a single species of humans stretching across the Old World, one that evolved over the past million years from small-brained hominids into our big-brained form.</p>
<div class="pullquote">
<p>Europeans and Asians carry a small portion of DNA inherited from Neanderthals.</p>
</div>
<p>But some researchers challenged this view. They pointed out that for thousands of years, Europe was home to the burly Neanderthals as well as slender humans. Neanderthals didn't give rise to living Europeans, these scientists argued; they were replaced by immigrants expanding out of Africa—perhaps even outcompeted into extinction.</p><p>Over the past 15 years, Svante Pääbo, a geneticist at the Max Planck Institute of Evolutionary Anthropology, and his colleagues have uncovered an entirely new source of evidence about the nature of Neanderthals: their DNA. Starting with those fossils from the Neander Valley, they extracted bits of genetic material that had survived tens of thousands of years. Eventually, they were able to assemble the fragments into the entire Neanderthal genome.</p><p></p>
<figure class="richtext-image full-width">
<img alt="Amazonian river" class="richtext-image full-width" src="https://staging.pbs.org/wgbh/nova/media/images/are-neanderthals-human-04.width-990_fcU43pz.jpg"/>
<figcaption>Populations of the same species that a river or other barrier divides can become unable to breed successfully with each other. Such an inability never occurred between Neanderthals and humans, who bred successfully at least once.
        
        <div class="credit">© thobo/iStockphoto</div>
</figcaption>
</figure>
<p>It's clearly different from the genome of any human alive today, sprinkled with many distinctive mutations. These mutations accumulated in a clock-like way, and by tallying them up, Pääbo and his colleagues estimate that Neanderthals and humans share a common ancestor that lived 800,000 years ago. It's possible that the ancestors of Neanderthals expanded out of Africa then, while our own ancestors stayed behind.</p>
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<h3>A question of breeding</h3><p>That's a long time—long enough to reasonably ask if humans and Neanderthals are indeed two separate species. Old species split into new ones when some of their members get isolated from the rest. If a river cuts the range of a species of frog in two, for example, the frogs on one side of the river may only be able to mate with one another. Each population will evolve along its own path. If they are isolated long enough, they will have trouble interbreeding. They may even be unable to interbreed at all.</p><p>From these facts of evolution, the biologist Ernst Mayr developed what came to be known as the Biological Species Concept in the 1940s—namely, a species is made up of members of populations that actually or potentially interbreed in nature. Experiments on living animals have shown that barriers to this interbreeding can arise in tens of thousands, or even just thousands, of years.</p><p>Once the Neanderthal lineage left Africa 800,000 years ago, did humans and Neanderthals have enough time to become unable to interbreed? Pääbo's research provides an answer: no.</p><p></p>
<figure class="richtext-image full-width">
<img alt="Ernst Mayr" class="richtext-image full-width" src="https://staging.pbs.org/wgbh/nova/media/images/are-neanderthals-human-05.width-990_Ef4j5J2.jpg"/>
<figcaption>Does the late Ernst Mayr's notion of what constitutes a species, which held sway for many decades, need to be scrapped or substantially revised? Many biologists believe so.
        
        <div class="credit">© Rick Friedman/Corbis</div>
</figcaption>
</figure>
<p>Europeans and Asians carry with them a small portion of DNA inherited from Neanderthals—while Africans do not. The best explanation for our mixed genomes is that after humans expanded out of Africa, they encountered Neanderthals and interbred. Comparing the different Neanderthal-derived genes in different people, Pääbo and his colleagues estimate that this encounter occurred around 40,000 years ago. The tiny amount of Neanderthal DNA has been interpreted by some scientists as evidence that Neanderthals rarely mated with humans—perhaps just once, in fact. But as scientists sequence more genomes from more human populations, they're exploring the possibility that our ancestors mated with Neanderthals several different times.</p><h3>A matter of survival</h3><p>The presence of DNA from Neanderthals in human genomes is compelling evidence that humans and Neanderthals could mate and produce fertile offspring. If we stick to the Biological Species Concept, then we are a single species, as Schaafhausen originally thought. But some scientists reject this argument. They think that Mayr's Biological Species Concept has worn out its usefulness.</p>
<div class="pullquote">
<p>Homo neanderthalensis and Homo sapiens endured—at least until the Neanderthals became extinct.</p>
</div>
<p>With the advent of gene sequencing, scientists have found that many animal species regularly interbreed. It's easy for any safari tourist to tell the difference between olive baboons and yellow baboons that live in Kenya, for example. And yet the two species regularly produce hybrids in the places where their species overlap, and they've been doing it for a long time.</p><p></p>
<figure class="richtext-image full-width">
<img alt="Neanderthal &amp; human skeletons" class="richtext-image full-width" src="https://staging.pbs.org/wgbh/nova/media/images/are-neanderthals-human-06.width-990_t97F2Cf.jpg"/>
<figcaption>What will it take for experts to agree on whether Neanderthals (foreground) and modern humans are one and the same species?
        
        <div class="credit">© Frank Franklin II/AP/Corbis</div>
</figcaption>
</figure>
<p>So why haven't the two baboon species merged into a single hybrid olive-yellow species? The baboons produced by interbreeding may not survive as well as purebred ones. They produce fewer offspring of their own, and so the genes from one species don't spread easily in the other. Thus, despite interbreeding—breaking Ernst Mayr's rule, in other words—the olive and yellow baboons endure as separate species.</p><p>Perhaps humans and Neanderthals were the same: They only interbred rarely, and when they did, the hybrid children couldn't fuse the two kinds of humans together. That may be why human and Neanderthal fossils remained so different.</p><p>William King would probably have been horrified at the notion of human beings having sex with Neanderthal "brutes." But despite this intermingling, <i>Homo neanderthalensis</i> and <i>Homo sapiens</i> endured—at least until the Neanderthals became extinct, and we survived.</p>
<div class="newsletter"></div>

<p>Neanderthals present a conundrum well known in biology: What exactly is a species?</p>

Science Ink #4 - "Vesalius Brain"

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<p>
<em>
   The latest “Science Ink” provides a closer look at the tattoo of Kristin Cattrano, an artist who spent fifteen years as a painter before deciding she was interested more in science than art.  Cattrano got this tattoo – a rendition of Andreas Vesalius’ “The Quivering Brain” – right before going back to school to study neuroscience.
  </em>
</p>
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<img alt="" class="richtext-image full-width" src="https://staging.pbs.org/wgbh/nova/media/images/brain__4VOdiwU.width-990_tNkZUju.jpg"/>
<figcaption>“Vesalius Brain” - Photos and Text Courtesy of “Science Ink: Tattoos of the Science Obsessed” by Carl Zimmer
        
    </figcaption>
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<p>
  For centuries, the medieval anatomists thought the best way to understand the brain was to read old books.  They would pore through the writings of Greek and Roman scholars, like Aristotle and Galen, to learn the true nature of the human body.  In the mid-1500’s, an anatomist named Andreas Vesalius realized at last that the doctors of the ancient world had not actually dissected humans.  They had dissected animals instead, and extrapolated to our own anatomy.  So Vesalius looked for himself, and drew pictures of the body’s interior unlike anything that had come before.
 </p>
<p>
  Check out more tattoos in
  <a href="http://carlzimmer.com/books/scienceink/index.html">
   “Science Ink:  Tattoos of the Science Obsessed”
  </a>
  by Carl Zimmer.
 </p>
</section>

Science Ink #11 - "Iceman"

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<p>
<br/>
<em>
   In this week’s science ink, Mike Goldstein revives the world’s oldest known tattoos, from the back of
   <a href="http://www.pbs.org/wgbh/nova/ancient/iceman-murder-mystery.html">
    Ötzi
   </a>
   , who died 5400 years ago in the Alps.  No one knows what the stack of lines meant to him.
  </em>
</p>
</section>
  

  
      609_a288.jpg' embedtype="image" format="fullwidth" id="7544"/&gt;
<p>
 “I got the tattoo to remind myself of my biological link to him,” Goldstein writes.  “Though we come from times that are completely different, we’re still both human, which is all we can be.  It reminds me that I can live however I want – I don’t have to work in an office or wear a tie, as are the expectations of our culture.  I can walk across the Alps and die in a swamp, and that’s OK.”
</p>
<p>
 Check out more tattoos in
 <a href="http://carlzimmer.com/books/scienceink/index.html">
  “Science Ink:  Tattoos of the Science Obsessed”
 </a>
 by Carl Zimmer.
</p>

Science Ink #10 - "Ascent of Man"

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<p>
<em>
   The latest science ink wraps around the torso of Chad Tatum, a software engineer at Georgia State University.  It comes from the 1862 book “Man’s Place in Nature,” by the British biologist Thomas Huxley.
  </em>
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</section>
  

  
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 The image may smack the modern tattoo-viewer as the clichéd march of progress, from lowly troglodyte to hunched caveman to modern human.  But it actually meant something different in Huxley’s book.  To understand why, one must turn back the clock suitably far.  In 1862, Darwin’s theory of evolution was still a raw new idea, having been unveiled only three years earlier.  Darwin himself was leery of delving into what his theory meant for humanity.  It was left to others, such as Darwin’s great champion Huxley, to start considering humans as evolved.
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 Huxley had no ancient fossils of intermediate forms to tie humans to other animals – those were decades away from discovery.  But he did have the anatomy of other primates to consider.  And he used the skeletons of gorillas, chimpanzees, and other “man-like apes,” as he called them, to drive home a shocking lesson.  Humans may be different from other species, but our skeletons are not far outside the range of variation found in other primates.  Tatum’s tattoo is not a march, but a reunion.
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 Check out more tattoos in
 <a href="http://carlzimmer.com/books/scienceink/index.html">
  “Science Ink:  Tattoos of the Science Obsessed”
 </a>
 by Carl Zimmer.
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Science Tattoo #9 - "Kevin Bonham" and the Tree of Life

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   In the latest Science Ink, an immunologist combines two powerful symbols – DNA and the tree – to create a “potent symbol of life.”
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 “The Tree Seems to be a potent symbol of life in human (at least Western) culture, and what better way to augment this symbol by putting the code for life (DNA) at its base?  I got this tattoo to commemorate the beginning of my Ph.D. in immunology,” writes Kevin Bonham.
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 Check out more tattoos in
 <a href="http://carlzimmer.com/books/scienceink/index.html">
  “Science Ink:  Tattoos of the Science Obsessed”
 </a>
 by Carl Zimmer.
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Carl Zimmer

Articles