In this week’s science ink, Mike Goldstein revives the world’s oldest known tattoos, from the back of Ötzi, who died 5400 years ago in the Alps. No one knows what the stack of lines meant to him.

“Iceman” - Photos and Text Courtesy of “Science Ink: Tattoos of the Science Obsessed” by Carl Zimmer

“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.”

Check out more tattoos in “Science Ink: Tattoos of the Science Obsessed” by Carl Zimmer.

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.

“Ascent of Man” - Photos and Text Courtesy of “Science Ink: Tattoos of the Science Obsessed” by Carl Zimmer

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.

“Ascent of Man” - Photos and Text Courtesy of “Science Ink: Tattoos of the Science Obsessed” by Carl Zimmer

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.

Check out more tattoos in “Science Ink: Tattoos of the Science Obsessed” by Carl Zimmer.

In the latest Science Ink, an immunologist combines two powerful symbols - DNA and the tree - to create a “potent symbol of life.”

“Kevin Bonham” - Photos and Text Courtesy of “Science Ink: Tattoos of the Science Obsessed” by Carl Zimmer

“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.

Check out more tattoos in “Science Ink: Tattoos of the Science Obsessed” by Carl Zimmer.

Bruce Jackson has us thinking about how DNA can help human beings trace their roots, but what about animals? Don’t they have DNA that chronicles their past as well? Carl Zimmer looks to Joshua Drew’s shoulder for answers.

“Joshua Drew” - Photos and Text Courtesy of “Science Ink: Tattoos of the Science Obsessed” by Carl Zimmer

There is no one kind of DNA. Every individual human, earthworm, liverwort, and bacterium carries a version of the molecule with a unique sequence. As living things reproduce and pass down their genes to their descendants, their DNA chronicles their genealogy. Joshua Drew, a conservation biologist at the University of Chicago, dives into the waters around the islands of Indonesia, trawling for DNA. The DNA happens to be in fishes, such as the checkerboard wrasse he had drawn on his shoulder, along with a segment of its DNA. The fishes can swim wherever they are so inclined; their larvae can drift for hundreds of miles in the currents. Yet their DNA, Drew Finds, reveals that they don’t travel far. It sheds light on one of the reasons for the ocean’s biodiversity: homebodiness.

Check out more tattoos in “Science Ink: Tattoos of the Science Obsessed” by Carl Zimmer.

As we learn about Bruce Jackson’s work tracing people’s roots, it feels like an appropriate time to explore a tattoo that gets to the heart of all of our roots. And besides which, we can’t help but love Lucy.

“Lucy” - Photos and Text Courtesy of “Science Ink: Tattoos of the Science Obsessed” by Carl Zimmer

“Here she is in all her 3.2 million year old glory,” he [James Chapel] says.

In 1974, a team of scientists digging in a remote corner of Ethiopia discovered the skeleton of Australopithecus afarensis. They nicknamed her Lucy, after the song “Lucy in the Sky with Diamonds,” which they had been listening to.

Lucy was far older than any hominin fossil found up until then, which made the fact that forty percent of her skeleton was still intact all the more remarkable. Instead of an isolated tooth or toe, the researchers could analyze a sizeable chunk of her body. Subsequent expeditions have discovered even more A. afarensis bones.

Lucy had legs and feet suited for walking on the ground, albeit slowly and inefficiently. She still had long hooked hands, which may have been useful for leaping into trees to escape leopards. And her brain was still tiny, measuring a third our own. In Lucy, we see how our ancestors stood upright long before they had our mental fire power.

For decades, Lucy stood at the outer edge of our understanding of human evolution. But in the 1990s, paleoanthropologists found several fossils of hominins that date back as far as 6.5 million years. Now Lucy stands midway along the journey from our common ancestor with chimpanzees to the six billion people on Earth today, a small, shuffling two-legged ape.

Check out more tattoos in “Science Ink: Tattoos of the Science Obsessed” by Carl Zimmer.

One of Ian Lipkin’s fellow virologists shares her tattoo of a vaccine tree, inspired by a verse from the biblical book of Revelation: “On each side of the river stood the tree of life, bearing twelve crops of fruit, yielding its fruit each month. And the leaves of the tree are for the healing of nations.”

“Vaccine Tree” - Photos and Text Courtesy of “Science Ink: Tattoos of the Science Obsessed” by Carl Zimmer

“I’m a virologist in a biotech company in Singapore,” writes Shi-Hsia Hwa. “Here’s my story: I’ve been interested in infectious diseases since I was a kid because my father almost died of TB when he was an infant, and his secretary was an older man with a pronounced limp from polio. I must have been the only kid who looked forward to mass vaccination days in school.”

Check out more tattoos in “Science Ink: Tattoos of the Science Obsessed” by Carl Zimmer.

The latest “Science Ink” provides a closer look at the forearm of Terrance Yee, an aerospace engineer who wears tattoos of the satellites he has helped build - like the DSX spacecraft, pictured here, which travels around the Earth in an oval-like orbit that takes it through belts of intense radiation that surround our planet. The satellite is equipped with devices that can remove radiation, which might be used to protect satellite from nuclear attacks.

“Satellite - Photos and Text Courtesy of “Science Ink: Tattoos of the Science Obsessed” by Carl Zimmer

“Small satellite missions are very demanding,” says Yee, “requiring total dedication to the mission and getting the job done on a tight budget and short schedule with really challenging new technology. In order to lead teams through this sort of development, you have to be 100% committed and very passionate about your endeavor. It can’t be just a job, but a calling, something that you recognize only a handful of people in the world are lucky enough to do. I’m inspired by the work I do and I hope the artwork I have inspires others to be as passionate as I am about space.”

Check out more tattoos in “Science Ink: Tattoos of the Science Obsessed” by Carl Zimmer.

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.

“Vesalius Brain” - Photos and Text Courtesy of “Science Ink: Tattoos of the Science Obsessed” by Carl Zimmer

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.

Check out more tattoos in “Science Ink: Tattoos of the Science Obsessed” by Carl Zimmer.

The latest “Science Ink” provides a closer look at the tattoo of Gabriel Pato, a Brazilian biologist. Per Zimmer’s post, the message of his tattoo is simple: the brain is a network.

“Neural Net” - Photos and Text Courtesy of “Science Ink: Tattoos of the Science Obsessed” by Carl Zimmer

Neurons send signals to thousands of other neurons, and it is the number and the strength of those connections from which our thoughts emerge. There is no single humunculus-like neuron in which a person’s mind resides. There is not even a single neuron for memories, or for smells, or for joy. Instead, our perceptions flow into layered networks, and out of those network come responses. If you like too far into the brain, you lose the forest for the trees.

Check out more tattoos in “Science Ink: Tattoos of the Science Obsessed” by Carl Zimmer.

This tattoo belongs to Vincent Pigno, a self-described “fledgling mathematician.” He wears it great, but we know a certain sleepy microbe hunter (our next scientist, Ian Lipkin) who could totally pull this one off.

“Micro Macro” - Photos and Text Courtesy of “Science Ink: Tattoos of the Science Obsessed” by Carl Zimmer

Among the things one can see with a microscope is a bacteria-infecting virus, called a bacteriophage, on Pigno’s left shoulder. Of course, a microscope lit by reflected sunlight wouldn’t quite be up to that particular challenge. Bacteriophages were first seen in the 1940s, thanks to the invention of more powerful scanning electron microscopes. Before then, many scientists doubted that bacteriophages even existed. Today, we know them to be the most common form of life on Earth, numbering an estimated ten to the thirty first power all told - that is, ten thousand billion billion billion.

Check out more tattoos in “Science Ink: Tattoos of the Science Obsessed” by Carl Zimmer.

Exciting announcement, Secret Lifers. This season, we invite you to look at a whole new side of scientists, one that many keep hidden under those draping lab coats: science tattoos. We’ll be featuring eye-popping images from the acclaimed science writer Carl Zimmer’s book, “Science Ink: Tattoos of the Science Obsessed,” along with reflections from the book on how each image relates to the scientist’s life and discipline.

Hear that? It’s the sound of science getting cooler than it already is.

“Solar System” - Photo and Text Courtesy of “Science Ink: Tattoos of the Science Obsessed” by Carl Zimmer

Whenever I went to the library, my mother always said, “Why don’t you get some kids books instead of planet books?” says Ira Klotzko, who grew up to get a Ph.D. in physics and start a software company.

Check out more tattoos in “Science Ink: Tattoos of the Science Obsessed” by Carl Zimmer.