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It’s a common mantra: in order to live a long healthy life, you must eat well and exercise. Extra pounds are extra years off your life, we hear. Your annoying aunt might believe this with her heart and soul. But the science isn’t so sure.

Today in Nature, reporter Virginia Hughes explained that there’s a lot of research suggesting that being overweight doesn’t always mean you life a shorter life. This is what many call the obesity paradox. Hughes explains:

Being overweight increases a person’s risk of diabetes, heart disease, cancer and many other chronic illnesses. But these studies suggest that for some people — particularly those who are middle-aged or older, or already sick — a bit of extra weight is not particularly harmful, and may even be helpful. (Being so overweight as to be classed obese, however, is almost always associated with poor health outcomes.)

This paradox makes public health campaigns far trickier. If the truth was at one extreme or the other—that being overweight either was or was not good for you—it would be easy. But having a complicated set of risks and rewards doesn’t make for a good poster. And public health experts really do want most people to lose weight and not put on extra pounds.

This is where researchers, public health policymakers and campaigners are starting to butt heads. A simple message—that fat is bad—is easier to communicate. But the science just isn’t that simple.

When a researcher from the CDC put out a study that suggested that excess weight actually extended life, public health advocates fired back, organizing lectures and symposia to take down the study. Katherine Flegal, the lead researcher on that study, says she was surprised by just how loud the outcry was. “Particularly initially, there were a lot of misunderstandings and confusion about our findings, and trying to clear those up was time-consuming and somewhat difficult,” she told Hughes. But the study was a meta-review, a look at a large group of studies that investigated weight and mortality. The research is there, Flegals says, and it suggests that weight isn’t necessarily the worst thing for you. And for Flegal, what public health people do with her work isn’t really that important to her. “I work for a federal statistical agency,” she told Hughes. “Our job is not to make policy, it’s to provide accurate information to guide policy-makers and other people who are interested in these topics.” Her data, she says, are “not intended to have a message”.

And the fight against fat hasn’t really ever been particularly effective. Not a single obesity drug or diet plan has been proven to last over a year, says Hughes in a blog. And much of our weight comes down to genes, she writes:

Friedman sees things quite differently, as he eloquently explained in a 2003 commentary in Science. Each of us, he argues, has a different genetic predisposition to obesity, shaped over thousands of years of evolution by a changing and unpredictable food supply. In modern times, most people don’t have to deal with that nutritional uncertainty; we have access to as much food as we want and we take advantage of it. In this context, some individuals’ genetic make-up causes them to put on weight — perhaps because of a leptin insensitivity, say, or some other biological mechanism.

So those who are the most prone to obesity might have the least ability to do anything about it. We’re not particularly good at understanding obesity and weight yet. Some of the key metrics that we use to study weight aren’t particularly good. Body Mass Index has long been criticized as a mechanism for understanding health. Dr. Jen Gunter blogged about Flegals’s study when it came out (she was critical of it) and explained why BMI might be the wrong tool to use to look at mortality:

BMI just looks at weight, not the proportion of weight that is muscle mass vs. fatty tissue. Many people with a normal BMI have very little muscle mass and thus are carrying around excess fat and are less healthy than their BMI suggests. There are better metrics to look at mortality risk for people who have a BMI in the 18.5-34.9 range, such as waist circumference, resting heart rate, fasting glucose, leptin levels, and even DXA scans (just to name a few). The problem is that not all these measurement tools are practical on a large-scale.

And while researchers argue over whether weight really does guarantee a shorter life and policy advocates try to figure out what to advocate, the weight loss industry rakes in billions of dollars every year playing to our fears and uncertainties.

More from Smithsonian.com:

The Culture of Obesity
Taking Childhood Obesity to Task
Mild Obesity May Not Be So Bad

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On Monday, Yahoo CEO Marissa Mayer said she wasn’t going to worry about ridding Tumblr of porn. “It’s just the nature of user-generated content,” she said.

In other words: Welcome to the Internet, there will be porn.

And Mayer is right. The numbers about just how much of the Internet is dedicated to porn are wildly variable, but they’re there. Some estimates put porn at 30 percent of all Internet traffic. Other places claim the percentage is far higher. Forbes put the question to neuroscientist Ogi Ogas, who studies our consumption of all things wicked, and heard that, in 2010, about 4 percent of websites were dedicated to porn and, between July 2009 to July 2010, about 13 percent of web searches were for some sort of erotica.

Now, some of that comes from the changing demographics of who uses the Internet, says Ogas. When the web was first formed, it was largely populated by dudes. “I think in 1999 that 4 or 5 of the top 10 searches on the Web were for porn,” he told Forbes. But now the uses and users of the Internet have increased dramatically. And while Internet users are still looking for porn, it’s not the only thing or even the most common thing they’re after.

But it is there. It’s there, and it’s easy to find. Which is why parents and lawmakers are still talking about it. In the UK, David Cameron announced that all porn sites would be blocked from public places, striving to create “good, clean WiFi.” Mirror News writes that the Prime Minister “stressed the importance of parents having confidence in public internet systems and that their children ‘are not going to see things they shouldn’t’.” And the UK isn’t the only place to talk about cracking down on porn. In Iceland, they’ve proposed to ban all online pornography—a curious turn for a generally liberal country.

Now, actually carrying these bans out is hard. You can’t just flip a switch and change the content of the Internet. The Economist explains why Iceland’s ban in particular would be hard, but the reasons stand for most porn bans:

Banning online pornography would be tricky. The definition of violent or degrading pornography would have to be clearly enshrined in law. Iceland would then have to police the internet, a difficult thing to do. When Denmark and Australia introduced online blacklists in an effort to block porn sites, some innocuous websites crept on to the lists by mistake.

Basically, actually rooting out which sites are porn and which aren’t isn’t as easy as it might sound. And, ban or no ban, porn will always be on the Internet for those who choose to seek it out.

This is why some places are arguing that rather than ban or regulate or stamp out porn, children and adults should simply be educated on the pros and cons of pornography. In the UK, where they want to ban porn from public wifi, 83 percent of parents felt that students should learn about pornography in sex education classes. In the United States, one class at Pasadena College takes porn head on. The course, Navigating Pornography, has students watch and discuss porn, and tries to debunk the myth that people should learn about sexuality through porn. “Students today live in a porn-saturated culture and very rarely get a chance to learn about it in a safe, non-judgmental, intellectually thoughtful way,” professor Hugo Schwyzer told the Huffington Post.

Buzzfeed visited Schwyzer’s class to see just what a course in porn might be like:

But in many places, where even regular sex education is hard to come by, the chances that students will learn about porn are slim to none. The National Children’s Bureau says that teaching about porn is crucial to giving children a well-rounded education about sex and relationships. Lucy Emmerson, Co-ordinator of the Sex Education Forum for the NCB, says that teachers are too scared to mention porn in class.  “Given the ease with which children are able to access explicit sexual content on the Internet,  it is vital that teachers can respond to this reality appropriately,” she says. “Whilst in some cases children find this material by accident, there are instances when they come across pornography whilst looking for answers to sex education questions; it is therefore wholly appropriate that pornography and the issues it reveals are addressed in school SRE.”

Basically, the reality is that ban or not, young people are going to encounter pornography on the Internet. Whether or not they’re ready for it seems to be up to their parents and teachers.

More from Smithsonian.com:

What Can We Learn From the Porn Industry About HIV?

The European Union Wants to Ban Pornography

Dawww. Photo: aaronz

Yellowstone National Park is a vast expanse of largely-untouched natural beauty, a tract of the west home to bears and wolves and geysers and mountains. But where humankind’s direct influence is deliberately kept to a minimum, that strategy of do-no-harm doesn’t always seem to work. For the past few decades, lake trout have been taking over the rivers and lakes in Yellowstone, pushing out the local Yellowstone Cutthroat trout. The Greater Yellowstone Coalition:

Yellowstone Lake and its tributaries once supported an estimated 3.5 million Yellowstone cutthroat trout. Since the illegal introduction of lake trout in the 1980s, the cutthroat population in Yellowstone Lake has plummeted. Catch rates for Yellowstone cutthroats have significantly dropped as more and more lake trout are caught every year. The precipitous drop in cutthroat numbers is a result of lake trout predating on cutthroat trout.

But more than just affecting cutthroat trout, the invasion of the lake trout is being felt throughout the ecosystem. According to new research lead by Yale’s Arthur Middleton, the replacement of cutthroat trout with lake trout is leaving Yellowstone’s local population of grizzly bears without enough fish to eat. Middleton and colleagues:

Historically, Yellowstone Lake harboured an abundant population of cutthroat trout, but lake trout prey heavily on cutthroat trout and have driven a decline of more than 90 per cent in their numbers. Although cutthroat trout migrate up shallow tributary streams to spawn, and are exploited by many terrestrial predators, lake trout spawn on the lake bottom and are inaccessible to those predators.

Without fish, the grizzlies need something, and in their place the bears have turned to eating baby elk.

In the late 1980s, grizzly and black bears killed an estimated 12 per cent of the elk calves in northern Yellowstone annually. By the mid-2000s, bears were estimated to kill 41 per cent of calves.

The researchers say that by turning to elk calves in place of the now-gone trout, the elk population growth rate has shrunk by 2 to as much as 11 percent. The research reminds that the food web is in fact a web, and that the illegal introduction of a few trout can mean a whole lot of dead elk.

More from Smithsonian.com:

Wolves and the Balance of Nature in the Rockies
The Return of the Elk

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In the animal kingdom, larger males—think chimpanzees, lions, bulls—often try to acquire or defend more resources, like territory, food, and females, than their weaker underlings. Researchers decided to apply the competitive animal model to human political decision making about redistribution of wealth and income to see if there was any correlation.

The Atlantic describes the study:

Researchers at Aarhus University in Denmark and UC Santa Barbara collected from several hundred men and women in Argentina, the U.S., and Denmark. They categorized the subjects by socioeconomic class, their upper-body strength, or “fighting ability” (as measured by the “circumference of the flexed bicep of the dominant arm”), and their responses to a questionnaire gauging their support for economic redistribution.

They hypothesized that men with more upper body strength would be less open to wealth distribution, following the same tendency of stronger males of many animal species. After all, upper-body strength has counted as a major component of dominance throughout human evolutionary history. When economics, strength and gender were taking into account, that hypothesis turned out to be true. Popular Science reports:

Socioeconomic status also showed a correlation with economic views. As expected, rich men were generally opposed to redistribution, and poor men generally in favor of it. Men with stronger upper bodies tended to have stronger views–rich, strong men were very much opposed to redistribution, while less strong but still rich men were less opposed. On the side of those that support redistribution, the trend was reversed: poorer but strong men were strongly in favor of redistribution, while weaker poor men were not as committed.

Political party had nothing to do with the results, the researchers found, and no correlation turned up between women’s opinion on the subjet and their physical strength and/or wealth.

The authors conclude: “Because personal upper-body strength is irrelevant to payoffs from economic policies in modern mass democracies, the continuing role of strength suggests that modern political decision making is shaped by an evolved psychology designed for small-scale groups.”

For many men, apparently, animal antics still hold strong.

More from Smithsonian.com:

Men of China’s Qing Dynasty Chose Trophy Wives to Flaunt Their Wealth 
Money Is In the Eye of the Beholder 

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In Croatia, scientists are working on a new way to detect land mines without risking lives, reports the Associated Press. Honeybees, the scientists say, have an incredible sense of smell, and with the right amount of prodding can be trained to sniff out TNT, the most common explosive used in land mines. In preliminary testing:

Several feeding points were set up on the ground around the tent, but only a few have TNT particles in them. The method of training the bees by authenticating the scent of explosives with the food they eat appears to work: bees gather mainly at the pots containing a sugar solution mixed with TNT, and not the ones that have a different smell.

A common technique in animal behavior training, the bees are taught to associate the smell of TNT with food. Once that association is firm, the bees can be turned loose in search of mines.

”It is not a problem for a bee to learn the smell of an explosive, which it can then search,” Kezic said. “You can train a bee, but training their colony of thousands becomes a problem.”

Bees, with their incredible sense of smell, light weight and ability to fly should be better candidates for mine hunting than other approaches. Mine decommissioning teams already use dogs and rats to hunt down mines. But, some anti-personnel mines are so sensitive that the weight of a pup can set them off. The bees’ training is still underway, says the AP, but if and when they’re ready the Croatian-trained bees will be able to flit from mine to mine without setting them off.

From 1999 to 2008, says the Guardian, 73,576 people reportedly died to hidden land mines or unexploded munitions. “Of these, around 18,000 were confirmed deaths – 71% of victims were civilians and 32% were children.” Aside from their destructive potential, land mines are also a psychological and social plight.

Landmines and cluster munitions have been described as “weapons of social cataclysm”, which perpetuate poverty and prevent development. They leave a legacy of indiscriminate civilian injuries and deaths, burden struggling healthcare systems and render vast tracts of land uninhabitable and unproductive. As Kate Wiggans, from the International Campaign to Ban Landmines and Cluster Munition Coalition (ICBL-CMC) says: “They keep poor people poor, decades after conflict.”

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Designer Creates Wind-Powered Land Mine Detonator