There will soon be seven billion humans on Earth, but how does that number compare to other species on the planet? We are certainly outnumbered by ants. Harvard biologist and ant expert Edward O. Wilson has estimated that there are a thousand trillion to ten thousand trillion ants at any one time.* That would be about a million ants for every one of us. And doesn’t it seem like that when they invade our kitchens? Estimating animal populations, especially wild ones, is hard, but here’s a look at one category of animals we can count: the ones we eat. —Nigel Holmes

Click to expand graphic.

*And they’re edible. Ants are a good source of protein and are considered a delicacy in many parts of the world.

Photo: Hugh Rose, Accentalaska

The critical habitat established to protect Alaska’s polar bears is the largest of its kind in the United States.

For the first time polar bears in the U.S. have their own critical habitat. The 187,157-square-mile swath around Alaska is mostly offshore, where roughly 3,500 Ursus maritimus dwell on sea ice—and large oil deposits may lurk. Set last fall, the Interior Department designation means all future drilling plans will be federally scrutinized (existing structures are exempt). It also protects barrier islands and the coastline where more mother bears are denning as sea ice melts.

Map: Jerome N. Cookson, NGM staff. Sources: IHS Energy; U.S. Fish and Wildlife Service. Click to enlarge.

So far, reactions have been mixed. The state of Alaska and Alaska Native corporations, which rely heavily on oil and gas dollars, say the red tape and the habitat’s vast size will spell huge revenue losses. Environmentalists cheer the move but fear it won’t be enforced. To save polar bears, they say, list them as endangered, not threatened. That would bolster legal protections and leave more room to tackle the chief threat to the animals’ territory: the greenhouse gas emissions causing climate change.
—Jeremy Berlin

From left: Aptenodytes forsteri (Emperor penguin), Inkayacu paracasensis, and Eudyptula minor (Little penguin)

Nothing is black-and-white, it seems. Not even penguins. That’s what University of Texas paleontologist Julia Clarke found after unearthing 36-million- year-old remains in Peru’s Paracas National Reserve—the first penguin fossil ever found with evidence of feathers intact. Like its present-day relatives, Inkayacu paracasensis was a deft swimmer. Unlike them, it weighed more than a hundred pounds and sported a coat with ruddy feathers. Clarke’s team deduced the color last year after comparing tiny pigment packages called melanosomes from the fossilized plumage with those of living species. This part of coastal Peru has recently produced other big penguin finds. Clarke says the area could be key to painting the full picture of the birds’ evolution. For now, a touch of color has been applied. —Catherine Zuckerman

Art: Mauricio Antón. Photo: Julia Clarke, University of Texas at Austin. NGM Maps

See the the full graphic of racial and ethnic intermarriages

Barack Obama made history when he became America’s first black president. His parents were pioneers as well: When they wed in 1961, interracial unions were illegal in more than a dozen states and fewer than one in 1,000 new U.S. marriages involved black and white partners. Now it’s one in 60.

A recent Pew Research Center analysis shows the trend has spread across races and ethnicities, with mixed unions reaching a record 14.6 percent of new marriages in 2008. The numbers reflect an immigration-fueled rise in the country’s minority populations, along with growing acceptance of mixed couples. (antimiscegenation laws ended in 1967 when the supreme court struck down Virginia’s ban.) Though immigrants do not tend to intermarry, their children do, says Pew senior demographer Jeff Passel.

Regionally, the West, with its high percentage of Hispanics and Asians, sees the most intermixing. Notes Passel: “As these couples have children, there will be more fuzziness in how race and ethnic groups are defined.” —Luna Shyr

In 1965 serpentine became one of America’s first state rocks. A California bill to oust it last year, based on its traces of asbestos, did not pass. But it did raise the question: Why do some states have official rocks? Experts say geology and economy are key. States rich in mineral deposits—and vested industries— anoint a rock or stone to promote pride and profit. Some share one. Those stuck without? Hard luck, indeed. —Jeremy Berlin

1 Serpentine California
2 Geode Iowa
3 Bauxite Arkansas
4 Slate Vermont
5 Thunder egg Oregon
6 Red granite Wisconsin
7 Agate Kentucky, Nebraska
8 Limestone Tennessee
9 Petoskey stone Michigan
10 Cumberlandite Rhode Island
11 Barite rose Oklahoma
12 Mozarkite Missouri
13 Roxbury puddingstone, Massachusetts
14 Marble Alabama, Colorado, Vermont
15 Coal Utah, West Virginia
16 Sandstone Nevada
17 Granite New Hampshire, North Carolina, Vermont

Photo: Rebecca Hale, NGM Staff

Designed to look like standard Indian currency, zero-rupee notes are larger and printed on thicker paper. That discourages folding, which is a common way for bribes to be passed. Photo: Rebecca Hale, NGM Staff  

In India, where corruption costs the public and private sectors millions of dollars a year, demands for petty bribes are frequently signaled in code: “Take care of me” or, for a two-note handout, “Make Gandhi smile twice.” Illegal demands by police and bureaucrats are “deeply ingrained in the culture,” says anticorruption crusader Vijay Anand, and are “taken as the norm.”

Graphic: A rich lunar portrait—and an early history of our solar system—is emerging from a wealth of fresh topographic data. See the enlarged lunar-surface map. Sam Pepple. Source: NASA Lunar Orbiter Laser Altimeter

Move over, man in the moon. Now there's more to see, thanks to the first detailed lunar-surface map. Since 2009 NASA's Lunar Reconnaissance Orbiter has been bouncing laser beams off the moon to gauge elevation. Last fall the results emerged as a high-resolution map, including a point over a mile higher than Mount Everest and a complete catalog of 5,185 craters wider than 12.5 miles. The impact pattern suggests that around 3.8 billion years ago two asteroid storms pelted the moon and the Earth, whose dynamic crust retains fewer celestial fingerprints.

Also newly found: frozen water in craters at the lunar poles—the coldest known spots in our solar system. "This is a renaissance period in moon studies," says NASA's Richard Vondrak. With surveys of Mars and Mercury also under way, more cosmic folklore may soon be jettisoned as well. —Jeremy Berlin

Don’t look to the stars for answers. On the clearest night only a few thousand are visible to the naked eye. And don’t even try counting to seven billion. Even if each number took just a second to say (and you didn’t lose your place), getting there would take more than two centuries. Seven billion steps would take you 133 times around the world (above). Watch the video for more ways to make sense of such a giant figure. —Thomas Pierce

 
Propelled solely by the sun, the world’s largest solar yacht set off from Monaco last fall.

A month into their quest to be the first to circle the world in a sun-powered ship, the European crew of the Tûranor PlanetSolar drew the curiosity of some locals in the Atlantic Ocean. “We stayed next to four magnificent sperm whales for nearly 20 minutes,” says the ship’s master, Patrick Marchesseau. “They seemed completely at ease with the silent visitor.”

A recently restored stepped pond in Rajasthan, India, dates from the 1500s. Photograph by Richard Cox. 

Roman aqueducts get most of the attention, but other ancient civilizations had notable waterdelivery systems too. India, for example, is pocked with thousands of deep, elaborately constructed cisterns known as step wells and stepped ponds.

Built as far back as the seventh century, both structures were used to collect rain and groundwater. To access the water—whether to drink, bathe, or worship—villagers descended stairs to its level. The wells' differences are architectural: Step wells are linear, with partly covered pavilions and stairs that face the water; stepped ponds are square, with open tops and zigzagging, Escher-esque stairs (above).

When British colonizers arrived in the 1800s, the wells were deemed unsanitary and fell into disuse. Today many are in states of decay, but lately a handful have been restored. The Indian National Trust for Art and Cultural Heritage aims to protect more of them—and possibly revive them for water harvesting in the country's arid regions. Architectural historian Morna Livingston supports the effort. "They're again a source of pride," she explains, "rather than a dump."—Catherine B. Zuckerman

Photograph by Richard Cox. NGM Maps

This spiny turtle, like other turtles, has an upper shell that forms as ribs widen and fuse into a bony plate.

Never mind Aesop and his fables. Japanese scientists are telling a new story of how the turtle got its shell. A shield from the elements and from predators, as well as a mineral reserve in low-oxygen environments, the turtle’s shell is unique in vertebrate anatomy. Still, a turtle’s embryo starts out looking like any spined animal’s—say, a chicken’s or a mouse’s. But about a third of the way through in-ovo development, says Shigeru Kuratani of the Riken Center for Developmental Biology, “an anatomical rule is violated” that remaps the animal’s physique. The ribs grow over the shoulder blades instead of under them as humans’ do, forcing the body wall to fold in on itself. What would have been an internal rib cage fuses into a bony plate under the skin and becomes a part of the turtle’s outer armor. In 2008 the fossil record delivered elegant support for this theory—and for another, more disputed one: that shells evolved from the bottom up. With a belly plate but an incomplete upper shell, 220-million-year-old Odontochelys semitestacea, found in China, seems an in-between form—one that looks a lot like an early stage in modern turtle development. More bony finds may someday tell the rest of the turtle’s story. —Jennifer S. Holland

Photo: Joel Sartore. Art: Hiram Henriquez
Source: Hiroshi Nagashima, Riken Center for Developmental Biology

Most of us know it as the gas that floats party balloons, blimps, and giant superheroes in holiday parades. But helium also purges rocket engines for NASA and the military and is crucial for diving equipment, particle accelerators, and MRIs.

The deflating news, says the National Research Council, is that we’re running out. Most of the world’s helium comes from beneath America's Great Plains, where it's trapped in natural gas. The U.S. began stockpiling it in the 1960s, but in 1996 opted to recoup its investment and sell off the reserve by 2015. After that, other producers—including Russia, Algeria, and Qatar—will control what’s left of the global market: perhaps a mere 40 years' worth.

Scientists, including Nobel Prize–winning physicist Robert Richardson, think increasing the price would help conserve the element. Richardson knows that charging big bucks ($100) for a little balloon is a partypooping idea. But it would also encourage the major helium users, like NASA, to recycle—and help the world hold on to its up, up, and away. —Gretchen Parker

Photo: Price of a helium balloon: 75 cents. What some say it should cost: $100. Photograph by Rebecca Hale, NGM Staff

Left: Daytime aerial photograph of Antwerp. Right: Nighttime aerial thermogram of Antwerp

Streets and badly insulated buildings give off heat at night and appear red; foliage and well-insulated structures look blue or green. Thermal colors also depend on roof shape (flat or slanted), roofing materials, and thermostat settings.

A nighttime flight over Antwerp, Belgium, last winter sought to separate the naughty from the nice. But it wasn’t slumbering children who were being judged; it was the buildings that housed them. That’s because in 2009 Antwerp and 20 other Flemish municipalities hired the geo-information firm Eurosense to create an aerial thermographic image showing how much heat was escaping through city roofs. A poorly insulated one can account for about 30 percent of a building’s total energy loss. In this image (above), the least efficient buildings and the city streets glow a bright red. Newer, more sustainable buildings—often insulated with materials such as spray foam or rock wool—appear as a cooler blue or green. Getting the full picture, however, requires a visit to the website zoominopuwdak.antwerpen.be, which lets residents plug in their addresses to learn how their building fares, as well as which government-sponsored loans and grants are available to those who improve their home’s energy efficiency. Now other cities in Belgium, as well as five in France and one in Germany, are following Antwerp’s lead—a sign that in some parts of Europe, coal deliveries will be down in December. —Aaron Britt

Archaeologist Mark Aldenderfer set out last year to explore remote cliffside caves in Nepal’s Mustang district, aiming to find human remains near an ancient settlement high in the Himalaya. Almost at once, he came face-to-face with what he was seeking: Jutting out from the rock, he recalls, 13,000 feet up, “a skull was looking at me right as I was looking at it.”

The skull, dating back perhaps 2,500 years, was among many human bones piled inside several burial caves. Aldenderfer and his team hope that DNA analysis will help pinpoint the origins of this isolated region’s inhabitants, who may have migrated from the Tibetan Plateau or points south.

More U.S. women are having children later in life, according to a new study from the Pew Research Center. Some possible reasons: higher education, fertility treatments, and changing attitudes toward marriage. While the overall birthrate in 2008 didn’t vary much from 1990, the number of babies born to women 35 and older rose a staggering 64 percent. Another factor, notes report co-author Gretchen Livingston, is that younger people were more likely than older ones to cite the economic downturn as a reason to delay pregnancy. Women in their late 30s to 40s “don’t really have that choice.” The same Pew report found that a record 41 percent of 2008 births occurred outside of marriage, up from 28 percent in 1990. And though most were to women under 25, older mothers are also less likely to be married these days. Which is not to say these moms are going it alone. The trend “comes largely from births to women who are cohabiting with the child’s father,” says sociologist R. Kelly Raley. “It’s clear that we think differently today than we did several decades ago.” —Cara Birnbaum

With a three-foot wingspan, an adult Rhinoptera bonasus can weigh 40 pounds.

Rays aren’t invasive newcomers here; in 1608 one stung explorer John Smith. But as predators like coastal sharks have declined, the observed spike in cownoses, though untallied, could be grounds for a carefully monitored fishery—and new revenue streams for watermen, retailers, and localities. Call it the new calamari? —Jeremy Berlin Photo: Henry Horenstein, Getty Images. NGM Maps

What’s left of the Aral Sea lies in present-day Kazakhstan (top third of photo) and Uzbekistan. Photo: Modis Image: Robert Simmon and Jesse Allen, NASA Earth Observatory

Seen from a satellite, today’s Aral Sea is but a cluster of green globs. The brown, beige, and white? Some 3,240 square miles of dirt, dust, and salt—a toxic mess blown by sandstorms and tied to local health problems and climate changes. In 1960 this was an inland sea the size of Ireland. But heedless river diversion—for irrigation to wrest cotton and rice from the Central Asian desert—and evaporation have shriveled it by 90 percent. Since 2005 a World Bank–funded dam has revived the northernmost lake’s fish and fishing industry. To help restore the rest, says Philip Micklin, geography professor emeritus at Western Michigan Univer sity, engineering money and political accord are key. If they don’t exist by 2020, much of this water won’t either. —Jeremy Berlin

DNA tests suggest C. psychedelica is millions of years older than its closest relatives.

The rocky, thickly wooded Vietnamese island of Hon Khoai is rarely visited by outsiders, much less foreign scientists. But Lee Grismer, a herpetologist at California’s La Sierra University, specializes in finding new species in remote areas. When he and his U.S.-Vietnamese team landed on Hon Khoai in 2008, the island did not disappoint: It yielded two new gecko species. The orange-purple-yellow-black Cnemaspis psychedelica caught Grismer’s attention as it lounged on granite boulders in the sunlight. “I couldn’t believe my eyes,” he says. “Most geckos are nocturnal, but these were out in the middle of the day.” The flashy colors, he says, may serve as a warning to predatory birds. DNA tests suggest the species dates back some 20 million years, older than any other in its genus. At a time when conservationists fret about worldwide declines in lizard populations, previously unexplored pockets of Southeast Asia may offer hope. Grismer and his team have already discovered 30 new reptiles there. “We’re finding new species hand over fist,” he says. “Diversity is on its way up in the areas where I work.” —Hannah Bloch

Map: Remote regions of Southeast Asia are yielding a trove of lizard discoveries.

Photo: Lee Grismer. NGM Maps

Chicken paws, called phoenix talons on some restaurant menus, are popular in China as snacks or dim sum items. Photo: Rebecca Hale, NGM staff

A trade dispute between the U.S. and China has caused an unlikely—and costly—flap in the global poultry market. The U.S., it turns out, is the Asian nation’s biggest provider of jumbo-size chicken feet. “The demand for paws in China is insatiable,” says poultry consultant Paul Aho. Light on meat but rich in gelatinous collagen, chicken feet are popular in China prepared in soy sauce or with pickled peppers and served with beer or tea. In contrast, the American appetite for them is so small that they were cooked down for uses such as animal feed before China opened up to U.S. chicken a decade ago. That might help explain the dramatic surge in U.S. paw exports to China and Hong Kong (left), which surpassed $350 million in 2009. But this year, following tensions over various trade issues, China imposed duties that sharply curtailed imports of U.S. chicken. Trade to Hong Kong, which has its own regulations, remains robust. Insiders say a mutually palatable resolution may take time. —Luna Shyr

Chart source: Richard Lobb, National Chicken Council

Not all moai were created equal; those with “hats” probably had higher status.

For centuries visitors have marveled at the mysteries of Easter Island’s 800-plus moai, colossal human figures carved of stone to represent ancestors. Equally puzzling are the red “hats” atop some statues—which 18th-century European explorers barely had time to admire before their own hats were brazenly stolen by islanders they met. Why the local fascination with headgear? Ancient Polynesians associated it with high status, so the moai’s cylindrical pukao likely signified certain statues’ importance. But how did multi-ton rounds of red scoria, a volcanic rock quarried up to eight miles from the moai, come to rest on these giant heads? The hats were apparently rolled to their destinations, and some experts believe they were maneuvered up ramps as high as 30 feet, perhaps by as few as ten men. The islanders “were incredible engineers,” says California State University archaeologist Carl Lipo, who’s mapped more than a hundred pukao with the University of Hawaii’s Terry Hunt. “They used the least amount of labor they needed to get something done—all without cranes.” —Hannah Bloch

Photos: Phil Marion (top); Press Association/AP images

Medical marijuana like this is federally supplied to only a handful of patients. Photo: Paul Wellman 

Here’s a sign that the times are a changin’: Nearly three out of four Americans say they favor legalizing medical marijuana in their state, according to a 2010 Pew Research Center survey. And 41 percent think all marijuana should be legal, up from 35 percent in 2008 and 12 percent in a 1969 Gallup poll.

White markings distinguish Giraffa camelopardalis peralta from Africa’s eight other subspecies.

Fourteen years ago the giraffes of West Africa were a neck away from extinction. A century of war, poaching, and habitat loss had nearly eradicated their range and their ranks, leaving fewer than 50. Yet today, says Julian Fennessy of the Giraffe Conservation Foundation, more than 220 are living alongside 80,000 farmers and villagers in a 150-mile-long zone near Niamey, Niger.

What accounts for this unlikely rebound? Expert Pierre Gay says conservation groups have extended micro-loans and agricultural aid to locals as an incentive to leave the animals be. The area also has ample food—acacia and Combretum leaves—and no predators, since hunters long ago wiped out the region’s lions and leopards. Finally, Niger banned giraffe hunting in 1998, when it realized it had a unique, 18-foot-tall tourist lure: West Africa’s only remaining herds.

Still, Fennessy warns that illegal wood cutting persists, that the population must reach 400 to be insulated from disease, and that individuals that have strayed from Niger’s “giraffe zone” into neighboring countries have been killed. The next step is to increase the zone—and with it hope for a complete comeback. —Jeremy Berlin

Photo: Rebecca Blackwell, AP Images
NGM Maps  

See the full illustration. Graphic: Oliver Uberti, NGM Staff. Art: Jason Lee

In 1960 a bathyscaphe took two men to the deepest point on Earth. In 2010 that manned descent to the Mariana Trench—still unmatched—won co-pilot Don Walsh the Hubbard Medal, National Geographic’s top honor for research and discovery. Yet it remains just a single, vital drop in an age of ocean exploration.

The secrets of the deep have emerged from research done far below the waves—and from far above them. Oceanographer Walter Munk deems the satellite TOPEX/Poseidon’s 13-year mapping of the sea surface, showing how currents affect climate, “the most successful ocean experiment of all times.”

What will the next century of marine science reveal? Maritime historian Helen Rozwadowski says that although most scientists think robotics are the way forward, some idealists still call for a Sealabstyle colonization of the sea. Either way, she says, environmental concerns will likely infl uence all future ocean exploration—“unless somehow the dreamers get our attention again.” —Jeremy Berlin

Visible from space, the world’s largest known beaver dam stretches across nearly 3,000 feet of wetlands in northern Alberta, Canada. Satellite Image: Digitalglobe

Deep within Alberta, Canada’s Wood Buffalo National Park, a massive engineering project is under way. The builders? Beavers. The job? Maintaining and expanding a dam likely begun by their ancestors decades ago. Today it’s more than half a mile long—the largest beaver dam known to exist.

Landscape ecologist Jean Thie spotted the structure in October 2007 while using satellite technology to study melting permafrost. “This is the beaver belt,” he explains, referring to the region’s now dense population, which has rebounded from near extinction since the fur trade ended. Level, remote land also benefits these animals, letting them build without the nuisances and threats of fast-flowing water and humans. That means freedom to gather branches and mud for lodging and food storage, two keys to beaver prosperity.

So how many beavers does it take to build such a dam? No one can say. But the colony is clearly vast—and resourceful. Says wildlife biologist Clay Nielsen, “Beavers are second only to humans in modifying their living space to fit their needs.” —Catherine Barker

That’s what went into the landmark Census of Marine Life, which unveils its full findings this month. Conceived by scientists Frederick Grassle and Jesse Ausubel, the $650-million survey—whose biggest funder was the Alfred P. Sloan Foundation—used everything from cutting-edge technologies to centuries-old fishing logs to find and ID species, map ecosystems, and assess data down to 16,000 feet.

“It’s an astonishing start,” says National Geographic Explorer-in- Residence Sylvia Earle. Yet with 95 percent of the ocean depths still unexplored, she says, a second census is warranted. “Don’t we want to know who shares the planet with us?” —Jeremy Berlin

Flicking its thick tail as it dashes up a tree, the fierce but shy Scottish wildcat can pass for one of its domesticated counterparts. This elusiveness is one reason sightings of the threatened feline are so hard to confirm. That tail, however, is telling: Its blunt, black tip and perfectly aligned rings hint that this is no muscular, oversize tabby.

These distinctions are some of the things the Highland Tiger Project aims to teach. Launched last year in Scotland’s Cairngorms National Park, the program, run by government and private groups, is raising awareness about the iconic cat, whose image adorns clans’ coats of arms but whose remaining numbers, possibly as low as 400, are confined to the rugged Highlands in the north. Disease, traffic fatalities, crossbreeding with feral and domestic cats, and—until recently—public ignorance have contributed to its decline.

Project manager David Hetherington knows education doesn’t end with identification, so he’s urging gamekeepers to be vigilant in areas where wildcats and human hunters compete for rabbits. He’s also asking people to neuter and vaccinate their pet cats. The effort seems to be working. Says Hetherington, “For years this cat has not been a priority. Now people are keen to save it.” —Catherine Barker

A Sherpa on Mount Everest sorts trash into plastics, metals, and biodegradables. Photo: Cory Richards

For 60 years climbers have dumped gear and trash en route to the top of Mount Everest, often in the low-oxygen “death zone” above 26,000 feet, where shedding a few pounds can preserve precious energy.

In recent years melting ice has begun to reveal the scope of the high-altitude imprint, exposing oxygen tanks and other long-frozen jetsam. Though tons of refuse are removed annually from base camps, last spring two Nepali groups, Extreme Everest Expedition and Eco Everest Expedition, targeted the peak’s upper reaches and hauled down seven tons of waste, including debris from a 1973 helicopter crash.

Nepalis are also concerned about corpses collecting on the mountain they consider holy. Since 1996 some 80 climbers have perished above base camp; most remain near the spot they died. In May two bodies, a Swiss and a Russian, were removed along with a pair of unidentified arms, one wearing a watch. Bringing back corpses was long considered logistically unfeasible, says Linda McMillan of the International Mountaineering and Climbing Federation. But as traffic on Everest has risen, she notes, so too has the desire to clean it. —Peter Gwin

Parts of ginger’s knobby rhizome can be removed without harming the plant. They’re the source of ginger products from powders to candies. The stringy danglers are the actual roots. Photo: Mark Thiessen, NGM Staff

“Take some ginger and call me in the morning.” That could become a new medical mantra—though it’s a very old idea. Indian texts from 1000 B.C. prescribe the herb for ailments from asthma to piles. Asian doctors still use it. Now skeptical Western ones are getting the word.

In a fresh study of 644 cancer patients, one group took the liquid equivalent of a half teaspoon of powdered ginger for three days before chemotherapy and three days after. Group members reported a 40 percent drop in feelings of nausea, says study co-author Julie Ryan, a professor at the University of Rochester Medical Center. The compound gingerol, a source of the herb’s heat, may block serotonins that send a nausea signal to the gut. Or it might help empty the stomach. Folks on chemo should ask a doctor before trying ginger; it could interfere with certain antinausea meds.

Ginger can also stave off motion sickness and is being tested as a balm for arthritis, notes UCLA oncologist Mary Hardy. A ginger fan, she keeps honey-based ginger candies in her purse—just in case. —Marc Silver

Hydration experts are ready to rewrite the popular dictum that people should drink eight glasses of water a day. Photo: Mark Thiessen, NGM Staff, with Dan Havens

Magazines, websites, even some medical texts recommend guzzling eight 8-ounce glasses of water a day. The bottled-water business loves it. Hydration experts, however, aren’t sure where the “8 x 8” rule came from—or whether it holds water.

Mike Sawka, a U.S. Army research scientist, thinks the origins lie in a 1933 study on rodent hydration. The research led to a recommendation of 2.5 liters a day, or 84.5 ounces of liquid, for a moderately active human to make up for water lost to sweat and excretions. Twenty percent typically comes from foods high in water—soup, ice cream, celery—leaving 67.6 ounces, or roughly “8 x 8.” (Exercise or heat adds to a body’s needs.)

Only you don’t need eight daily glasses of water. Other beverages count, even if caffeinated. “The body’s need to keep fluid trumps the small influence caffeine might have on losing fluid,” says University of Connecticut exercise physiologist Douglas Casa. Plus the body isn’t shy about liquid desires. Drink if you feel thirsty. If not, don’t. One exception: Hydrate before an intense workout.

When in doubt, check your urine. Dark yellow, says University of Pennsylvania nutritionist Stella Volpe, is the hue of dehydration. —Marc Silver

Never mind the World Cup or Super Bowl. With a bevy of volcanoes in various states of agitation, a Dublin bookie offers the chance to cash in on the ones that blow.  Photo: Odd Stefan Thorisson, Nordicphotos/Corbis  

It’s an investment even more volatile than stocks: the next big volcanic eruption. Well before Iceland’s Eyjafjallajökull blew this year, Ireland’s largest bookie, Paddy Power, was letting punters bet on the peak they deemed most likely to explode. The seven-to-four favorite? Another Icelandic peak, Katla. Eyjafjallajökull now sits in fourth place, along with Hawaii’s Mauna Loa (ten to one). Unlikely to go off, but with a big purse if it does: Yellowstone (50 to one). “Volcanoes with regular lava flows or burps are hot favorites,” says Paddy Power spokesman Darren Haines. “Dormant volcanoes can see odds as low as 500 to one.” Probabilities are calculated using the Volcanic Explosivity Index—the scale, ranging from zero (nonexplosive) to eight (megacolossal), that scientists use to rank eruption severity. The first volcano to hit level three, with plumes at least two miles high, will prompt payouts. Paddy Power’s clients came up with the novel market after the 2009 eruption of the Philippines’ Mount Mayon. If natural phenomena aren’t your thing, this year’s bets have also included the next Oscar winners, pope, and James Bond actor—and which country will make first contact with space aliens. (Ireland and the United States were top picks.) On a more somber note, one could have wagered on how many wild polar bears will exist as of the end of 2011 and how many species will be critically endangered. Here’s hoping the odds land in the animals’ favor. —Jennifer S. Holland

Cilantro is the leaf of the coriander plant. Detractors say even one small sprig tastes strongly of soap. Photo: Mark Thiessen, NGM Staff 

Cilantro is one polarizing herb. The seemingly innocuous staple of Mexican, Asian, and Indian cuisines has become a fresh ingredient in news stories and inspired passion-fueled blogs. Fans liken its notes to those of citrus; haters say they smack of soap. Whichever side of the produce aisle you’re on, solidarity abounds. Yet it isn’t simply a matter of taste. According to Charles Wysocki of the Monell Chemical Sense Center, it’s actually about fl avor, which the brain perceives based on a complex combination of taste, smell, heat, texture. In the case of cilantro, Wysocki has a hunch that genes play a role too. His ongoing study of twins shows that identical ones have the same reaction to it far more often than fraternal ones do. The genetic verdict is still out, but one thing is certain: In California, where annual records are carefully kept, cilantro production has doubled in the past decade. Agricultural economist Gary Lucier says Americans are eating on average at least a third of a pound of it a year, likely due to our increasingly diverse culinary scene. Does that taste like victory, or work you into a lather? —Catherine Barker

A Calakmul mural shows two vessels of corn gruel—a pot balanced on a woman’s head and a man’s sipping bowl. Photo: Kenneth Garrett. Graphics: Hiram Henriquez. Source Calakmul Achaeological Project. 

Colorful murals revealed at the site of Calakmul in southern Mexico offer a first ever look at daily activities that once animated great cities ruled by powerful kings. Painted on a pyramid in the seventh century, the murals’ scenes show residents transporting and consuming an array of common goods. Hieroglyphs provide job titles—“corn gruel person,” for example, and others in charge of tamales, tobacco, and pottery. Words never seen before in Maya texts are especially intriguing— ixim for “raw corn” and atzaam for “salt,” both important staples. At other sites, monumental art shows mythical scenes as well as finely dressed gods and nobles engaged in wars and rituals. At Calakmul, figures wearing holiday tunics, loincloths, and headbands give experts a new view of Maya society. “We think these scenes represent a festival celebrating an event such as a king’s accession to power,” says head archaeologist Ramón Carrasco Vargas. Panels yet to be excavated may hold further details of Calakmul’s citizens and how they went about their business. —A. R. Williams

Recovered artifacts bear witness to lives and buildings lost on September 11, 2001. Photos: Ira Block; Source: National September 11 Memorial & Museum

If every object tells a story, the ones displayed here speak of thousands with a common ending: a Georgia man whose wife slipped him a love note 1 for his trip to New York City; a woman with prayer beads 2 at work on the 98th fl oor of the World Trade Center; a husband who always carried a two-dollar bill 3 to remind him how lucky he was to have met his second wife. Collected for the National September 11 Memorial & Museum, the objects tell of love, faith (Bible pages fused to metal 4), lifestyles (a Mercedes key 5 and a golf ball 6), and a workday (computer keyboard 7) that came to a tragic end in 2001. The museum, set to open in September 2012, has some 3,000 artifacts so far, hundreds of them bestowed by relatives of those who perished. A ladies’ shoe 8 is one of several objects here that belong to survivors. The four-inch heels carried their owner down 62 fl oors, away from the crumbling south tower, and across the Manhattan Bridge to safety.

—Luna Shyr

The regeneration process went slightly awry for this day gecko, which lost its tail—and grew back two. Photo: Joel Sartore

To escape a predator, it doesn’t cost some lizards an arm and a leg—just a tail. The wiggling appendage is left behind as a distraction as the lizard gets away. Special cells at the fracture site then trigger growth of a new tail. Several amphibians and reptiles possess an ability to regrow portions of a lost tail or limb. Now some of the cells that make this happen are getting attention from researchers. A 2010 Harvard review of amphibian regeneration-cell research included how findings could relate to human stem cells, which can also produce new tissue. “The promise will be to figure out what’s the same and what’s different about regeneration mechanisms,” says Cliff Tabin, a geneticist who worked on the review. He hopes scientists will learn how animals that regenerate “get limbs and muscle, then hook that up with the bone, and have nerves seamlessly connect to the rest of the nervous system.” Even if animal and human cells aren’t found to regenerate in similar ways, the comparison “can give us a direct model to be applied to clinical studies,” says Tabin. “It’s a creative way to improve human health.” —Dana Cetrone 

Within the velvety shell of its coconut-size fruits, Africa’s iconic baobab packs a huge amount of nutrition. Its fruit contains six times as much vitamin C as oranges, twice as much calcium as milk, and plenty of B vitamins, magnesium, iron, phosphorous, and antioxidants. Until very recently those nutrients were enjoyed only by locals who ate the fruit fresh or crushed the crumbly pulp to stir into porridge and drinks. Few beyond the continent have been able to taste the baobab’s distinctive tart flavor, described by Lucy Welford, of PhytoTrade Africa, as “somewhere between grapefruit, pear, and vanilla.” Now baobab is headed to stores in Europe and the United States as an ingredient in jams and pepper sauces and, eventually, cereal bars and smoothies. The European Union has approved the sale of baobab food products. Already, women in Malawi are harvesting the fruits for commercial use and earning enough cash to pay children’s school fees. Will baobab ever be as trendy as the acai berry? Experts estimate the potential size of the international market at a billion dollars a year. “Baobab is moving from cottage industry into the mainstream,” says Malcolm Riley, of the Yozuna jam company in England. He now counts a large chain of British food stores among his customers. “It’s got mass potential.” —Karen E. Lange

The millions of Humboldt squid, aka jumbo flying squid, live “fast and furious” lives, says NOA Fisheries oceanographer Ken Baltz. “They hunt and eat and hunt and eat” for a year or two, then expire. Their diet is mainly fish, an occasional floating seabird—and sometimes each other. Once in a great while they “fly” by ejecting themselves from the water. Given that a squid’s body plus tentacles can run six feet and top the scales at 80 pounds, that’s quite a feat. Flight might be a way to evade predators, although scientists don’t know exactly why squids soar. Nor do they understand why the squid can quickly change from red to pink to maroon: maybe to confuse prey, maybe to signal each other.

Now this warm-water denizen is in the news because of an unexpected incursion into the northern Pacific. Its big appetite will surely affect the ecosystem. If salmon are also on the menu, adds William Gilly, a biologist at Hopkins Marine Station of Stanford University, Northwest fisheries will suffer. But he doesn’t buy reports of summer 2009 attacks on San Diego scuba divers. A squid might nudge with a toothed appendage to assess edibility, he says. “They’re smart and curious and really tactile.” Anyone in a wet suit would be deemed unfit for cephalopod consumption. —Marc Silver

“Make thee an ark,” the Lord told Noah in the Book of Genesis, and forever after the ark has been pictured as an animal-filled boat with a conventional prow and stern. Now a recently translated Babylonian tablet (above), related to the Epic of Gilgamesh, floats an intriguing alternative in which the archetypal ark was round and made of pitch-covered reeds, much like a coracle, a craft still used today on the Euphrates and Tigris Rivers.

“The ark wasn’t going anywhere,” explains Irving Finkel, assistant keeper of cuneiform at the British Museum, who did the translation. “It simply had to bob along the surface until the waters went down.” The author of the 4,000-year-old clay tablet might have glanced out his window at the vessels on the river and adapted the detail to his story. Flood myths appear in many cultures, and this one had circulated for eons before it was incorporated into the Bible. Finkel thinks the Babylonian version may have been a precursor to the familiar Hebraic one. While the shape of the ark may vary according to the teller, a basic narrative thread holds: Man was flawed. Revision was required. Best to wipe the slate clean and start again.

Every batter and tennis pro knows the best thwack comes when the ball hits the equipment’s sweet spot. Turns out glyptodonts, giant armored mammals that lived from about 30 million to 10,000 years ago, were using that center of percussion, as the spot is known, to strike hard blows with their battle-ready tails.

Fossil evidence tells us that some of the largest of these armadillo kin wielded spiked clubs weighing up to 140 pounds, joined to the body by a series of bony rings. Now biomechanical studies by Uruguayan scientist R. Ernesto Blanco and colleagues suggest that glyptodont fights didn’t involve random swinging of arms. While smaller species had mobile tails for quick swipes at predators like carnivorous birds, the largest ones had stiffer tails with a sweet spot at or near their prime spike. This morphology allowed the beasts to nail foes while minimizing harmful vibrations to the body joint from the force of impact. The big guys could afford this adaptation, which limited the tail’s speed and range of motion but, Blanco theorizes, offered a particular advantage during slow, ritualized courtship battles over favored females. How sweet is that? —Jennifer S. Holland

Hiking in a Nova Scotia park last fall, a young woman was killed by two canids. They were bigger than coyotes and smaller than wolves, with skulls and jaws unlike either species’. Some eastern Canadians and Americans had glimpsed “coywolves” before, but the grisly incident conjured fresh questions. What exactly are they? And should we be worried? 

Roland Kays of New York State Museum can answer the first one. In the 1920s, he says, coyotes from the west pushed into the Great Lakes region and mated with wolves from the east. The result wasn’t a new species but, according to recent DNA analysis, a hybrid that’s more coyote than wolf, with the street smarts of the former and the hunting capabilities of the latter. No one knows their current numbers, but eastern coyotes (the favored term) form families, seek food at night, and can prey on pets and livestock—the main reason for their recent run-ins with humans. 

As for worrying, Cape Cod wildlife specialist Peter Trull says there’s no need to; the Nova Scotia case was an anomaly. “Coyotes are wild animals, and people have been bitten by them,” he says. “But generally they avoid humans.” —Jeremy Berlin

A great hammerhead shark prowls the waters of the northern Bahamas. Photo by: Brian Skerry, National Geographic Stock.

A Shark’s-eye View Why are hammerhead sharks’ eyes so widely separated on their bizarrely shaped heads? Whatever the evolutionary reason for the placement, scientists have debated whether it was to provide good vision. Florida Atlantic University marine biologist Michelle McComb has settled that vision question by studying three of the eight types of hammerheads. She found that hammerheads see not only directly ahead with binocular vision similar to that of humans; they also see up, down, and behind themselves simultaneously. “Their eyes are canted forward, and that is the key,” McComb says. Their eye separation gives hammerheads great binocular vision and depth perception—a bonus when pursuing fast-moving prey.

Although hammerheads do have a particularly big blind spot in front of their widely spaced eyes, other senses compensate for this hole in their visual field. Sensors on the sharks’ heads help them detect electrical fields emitted by fish, and the placement of nostrils near their eyes could mean they use what McComb calls “enhanced stereo smell” to monitor the blind spot. —Jim Dawson

The Nabataeans hewed this partially completed tomb from a rock outcrop in the Arabian desert. Photo: Hubert Raguet, Look at Sciences. 

Lots of people know of Petra, capital of the long-lost Nabataeans. It’s the red sandstone city, carved into Jordan’s cliffs, where Indiana Jones found the Holy Grail.

But Hegra, another large city of this ancient civilization of caravan traders, is far less known. Called Al Hijr in Arabic, it is in northwestern present-day Saudi Arabia. Twenty-nine of its 111 monumental tombs have dated inscriptions; most of Petra’s are curiously bare. The Hegra carvings allowed archaeologists to date both cities to about 2,000 years ago. Later the Nabataeans vanished into the Roman Empire, and Hegra lapsed into ruin. Locals, believing the pre-Islamic city cursed, long discouraged visitors, as did the restrictive Saudi government. But the Saudis relented, and in 2008 Al Hijr became Saudi Arabia’s first UNESCO World Heritage site. Archaeologists are now welcome, and tourists are too. —Chris Carroll

E. chlorotica’s leafy, two-inch-long body lets it efficiently capture sunlight for photosynthesis. The chlorophyll in its cells makes the slug green. Photo by: Nicholas Curtis and Raymond Martinez

Sun-Loving Slugs Plants, you aren’t so special. That’s the message from the marine mollusk Elysia chlorotica (above), which not only looks like a leaf but acts like one too. The slug can live on sunlight its entire life, up to a year; all it needs is a little yellow-green algae.

Capturing energy from the sun by photosynthesis is best known as a plant thing. But decades ago marine biologists realized that sea slugs steal cellular bits called chloroplasts from the algae they eat and use them to turn CO2 into sugar. In 2007 the slugs were shown to incorporate algal genes into their own DNA. This lets them make the plant proteins needed to keep chloroplasts in their cells long-term.

Now University of South Florida biologist Sidney Pierce and colleagues report that the Atlantic-dwelling E. chlorotica filches enough plant genetics that it can churn out its own chlorophyll, the pigment that chloroplasts exhaust during photosynthesis. That means the green slug can use the sun to refuel without ever eating again.

Pierce says it’s an intriguing evolutionary shortcut: “Movement of genes between species can make big and rapid changes. Evolution doesn’t always need to wait for a mutation.” —Jennifer S. Holland

Learn more about wildlife on the new TV network Nat Geo WILD.

Scottish Highland cattle, such as this bull in the Netherlands, will be used in early efforts to bring back aurochs. Photo: Ardi Hoogendijk, Foto Natura/Minden Pictures.

For centuries they roamed Europe’s forests—massive bovines called aurochs that were depicted on cave walls by Paleolithic artists (inset) and prized as hunting trophies. They died out nearly 400 years ago. Now genetics may bring them back to life.

Sound like a Jurassic Park sequel? It’s actually the real-life plan of Project Tauros, a consortium of European scientists using DNA sequenced from aurochs teeth to steer a novel breeding program. Project researchers are currently identifying living cattle—including Spanish Limiana and Italian Maremmana—that still carry aurochs genes. Then breeders will cross those cattle to retain the pertinent DNA, jettison the rest, and make bovines that, in about a decade, are expected to look and act just like their extinct ancestors.

Photo (Composed of 55 Calibrated Images): Miloslav Druckmuller, Peter Aniol, Vojtech Rusin.

Total solar eclipses occur every 18 months or so and are visible for just a few minutes from any one spot. As knowledge about them has trumped superstition, legions of fans have been flocking to the narrow strips on Earth where the moon can best be seen obscuring the sun.  The reward for these so-called umbraphiles, says Williams College astronomy professor Jay Pasachoff, is “the most dramatic natural phenomenon ever visible. It’s spectacularand fills you with awe. A primal feeling comes over you.”

This year Melita Thorpe, owner of an astronomy-themed travel agency, saw a hundred slots fill up by spring for a $6,000 July freighter trip to the South Pacific; dozens more devotees signed up for a sunset viewing of the same eclipse in Patagonia. Her biggest crowd in the agency’s 26 years: the 700 people she ferried to view a 1991 eclipse off the coast of Mazatlán, Mexico.

The spotlight on pomegranates may shift from seeds to rind. Photo: Rebecca Hale, NGM Staff 

Pomegranates are famous for their jewel-like seeds, whose rich antioxidant stores may help prevent heart disease and certain types of cancer. But some of their most promising health benefits could dwell within their inedible rinds. 

A group of Kingston University researchers in London found that a mixture of pomegranate-rind extract, copper salts, and vitamin C can significantly reduce the growth of some common hospital bacteria. Declan Naughton, head of the study, says the fruit could be a new weapon in the battle against methicillin-resistant Staphylococcus aureus (MRSA), which can cause serious skin, blood, and soft-tissue infections. Ironically, the antibiotics used to banish MRSA have spawned even heartier strains—and more people outside of hospitals are catching it. 

The high levels of antimicrobials in pomegranate rind that protect the fruit’s flesh from harmful bacteria might do the same for humans, says Naughton. An ideal application, with further research, could be an ointment for cuts, abrasions, or surgical wounds. “Once something gets inside your bloodstream, it’s difficult to treat,” he notes. Another potential benefit: “We don’t think it would have major side effects, because we’ve looked to nature to show the way.” —Cara Birnbaum

In the matriarchal world of elephants, males are known as mostly independent sorts. Females maintain close, lifelong family ties, while bulls tend to wander off solo, at times banding with another male or more loosely with groups of them. 

Or do they? During a six-year study in Namibia’s Etosha National Park, Stanford University behavioral ecologist Caitlin O’Connell-Rodwell observed for the first time intense, long-lasting bonds among a dozen or so bulls—a tight-knit group of teenagers, adults, and seniors up to 55 she’s dubbed the Boys’ Club. Older males serve as mentors and mediators for younger ones, enforcing a strict social hierarchy and keeping underlings in line when hormones rage and rowdiness may erupt.

In drought-prone Namibia, rank becomes most rigid when water is scarcest. “In dry years the strict pecking order they establish benefits all of them,” O’Connell-Rodwell says. “Everyone knows their place.” That means young bulls supplicate more frequently to their elders—and peace is maintained while everyone gets to drink. —Hannah Bloch 

Learn more about wildlife on the new Nat Geo Wild network. Visit http://natgeowild.com.

Spearing lions used to be a rite of passage for young Maasai men. Now some warriors are guarding the big cats instead. As Africa’s exploding human populations vie with wildlife for land and resources, the number of lions speared, shot, snared, and poisoned has soared, imperiling the species. As few as 20,000 now remain. In response, Living With Lions, funded by the NGO Panthera, has hired tribesmen to protect their former foes. Warriors track lions, help cattle owners build lion-proof corrals, and educate Maasai communities on lions’ value. One study in Kenya found that each cat kills livestock worth $290 a year, yet brings in $17,000 in tourist revenue. Nevertheless, some experts warn that within 25 years there may be no lions left outside of the biggest, best run parks. Wildlife biologist Craig Packer says for lions to survive, parks must be fenced and heavily guarded—perhaps by the United Nations. —Karen E. Lange

This juvenile skull from Malapa cave emerged once the surrounding limestone was teased away. Photo: Brett Eloff 

Ninety miles above the Arctic Circle, the Swedish municipality of Kiruna is in trouble. The town center, population 18,000, sits atop one of the world’s largest iron ore mines. After 110 years of mining and more than a billion tons of ore, huge cracks deform the bedrock, and Kiruna must either see the mine shut down or move out of harm’s way. What to do? Well, move, of course. Residents, many of whom depend on the mine for jobs, have decided to gradually relocate central houses, shops, and even a 98-year-old wooden church (below) to more stable ground several miles away. Some buildings will be transported brick by brick; many will be constructed anew. Among the fi rst to go: the 1899 house of Kiruna’s founder. Railroad tracks, roads, and electricity lines have already started to migrate. The iron mine, key to new Kiruna’s survival , will remain active—but at a safer distance. —Hannah Bloch

 
A vapor cone blooms around an F-22 Raptor as it races through humid air during a supersonic flyby. Photo: Ronald Dejarnett, U.S. Navy

The problem: how to break the sound barrier without rattling windows or nerves on the ground below. NASA’s Dryden Flight Research Center is learning how to lessen sonic booms. With barrier-busting airplanes, says Dryden aerospace engineer Edward Haering, “you get shock waves at each gradation in the vehicle’s shape.” It’s when individual shocks from the nose, wing, and tail come together that we hear the thunder down below. That makes a streamlined design a first goal for less jarring supersonic flight. An experimental narwhal-tusk-like “quiet spike” on the nose can help mellow an aircraft’s boom. Newer designs seek to shape shock waves from across the plane to keep them from coalescing into a megaboom. “We think we’re close to having the right tools to design it,” says Haering. “All we’ll need then is the will to build it.” Which could mean, finally, flying from New York City to Los Angeles in less than three hours, without waking up everybody in between. —Thomas Hayden