Six-eyed sand spiders make their living by hiding, burrowing into the sand where they lie in wait of passing prey. Given that, it's a bit surprising how ... cute ... the process of burrowing looks. All I could think while watching this video was, "Awww, who's a happy spider?"

Boldly going where nobody's gone before. In a lot of ways, that idea kind of defines our whole species. We travel. We're curious. We poke our noses around the planet to find new places to live. We're compelled to explore places few people would ever actually want to live. We push ourselves into space.

This behavior isn't totally unique. But it is remarkable. So we have to ask, is there a genetic, evolution-driven, cause behind the restlessness of humanity?

At National Geographic, David Dobbs has an amazing long read digging into that idea. The story is fascinating, stretching from Polynesian sailors to Quebecois settlers. And it's very, very good science writing. Dobbs resists the urge to go for easy "here is the gene that does this" answers. Instead, he helps us see the complex web of genetics and culture that influences and encourages certain behaviors at certain times. It's a great read.

Not all of us ache to ride a rocket or sail the infinite sea. Yet as a species we’re curious enough, and intrigued enough by the prospect, to help pay for the trip and cheer at the voyagers’ return. Yes, we explore to find a better place to live or acquire a larger territory or make a fortune. But we also explore simply to discover what’s there.

“No other mammal moves around like we do,” says Svante Pääbo, a director of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, where he uses genetics to study human origins. “We jump borders. We push into new territory even when we have resources where we are. Other animals don’t do this. Other humans either. Neanderthals were around hundreds of thousands of years, but they never spread around the world. In just 50,000 years we covered everything. There’s a kind of madness to it. Sailing out into the ocean, you have no idea what’s on the other side. And now we go to Mars. We never stop. Why?”

Why indeed? Pääbo and other scientists pondering this question are themselves explorers, walking new ground. They know that they might have to backtrack and regroup at any time. They know that any notion about why we explore might soon face revision as their young disciplines—anthropology, genetics, developmental neuropsychology—turn up new fundamentals. Yet for those trying to figure out what makes humans tick, our urge to explore is irresistible terrain. What gives rise to this “madness” to explore? What drove us out from Africa and on to the moon and beyond?

Read the full story

Underwater, Antarctica's Weddell seals are fast-moving, graceful predators, catching and eating as much as 100 pounds of food per day. They dine on squids and fish and have been known to enjoy the occasional penguin or two.

On land, they are hilariously ineffectual blobs of jelly.

You can see that dichotomy in action in this great (and long) video made by Henry Kaiser in Antarctica. Following the adventures of a baby seal on the ice and under the water, the video is peaceful, meditative and reminds me a bit of the sort of old-school Sesame Street video that would build simple, kid-friendly narratives out of nature footage and music. (The music, by the way, was written and performed by Henry Kaiser, as well.)

Despite their poor performance in land-based locomotion, Weddell seals actually live on the ice, descending into the water to hunt and mate and swim around. They use natural holes in the ice to get from above to below and back, but they also work to maintain those holes and often use their teeth to chew at the edge of the ice and make a small hole larger. At about 13 minutes into the video, you can watch a seal doing just that — rubbing its head back and forth to enlarge an opening in the ice.

And why hang out on the ice, to begin with? Simple. In the water, seals are, themselves, potential dinners for larger creatures. On land, they have no natural predators at all and can safely bask in the sun, lying on their cute and chubby bellies for so long that their body heat hollows out divots in the ice.

Written by Dan Buettner, the piece focuses on the Greek island of Ikaria, and, in many ways, it's a lot like a lot of the other stories I've read on this subject. From a scientific perspective, we don't really understand why some people live longer than others. And we definitely don't understand why some populations have more people who live longer. There are lots of theories. Conveniently, they tend to coincide with our own biases about what we currently think is most wrong with our own society. So articles about extremely long-lived populations tend to offer a lot of inspiring stories, some funny quotes from really old people, and not a lot in the way of answers.

Buettner's story has all those elements, but it also proposes some ideas that were, for me, really thought provoking. After spending much of the article discussing the Ikarian's diet (it's low in meat and sugar, high in antioxidants, and includes lots of locally produced food and wine) and their laid-back, low-stress way of life, Buettner doesn't suggest that we'll all live to be 100 if we just, individually, try to live exactly like the Ikarians do. In fact, he points out that other communities of long-lived individuals actually live differently — Californian Seventh-Day Adventists, for instance, eat no meat at all and don't drink, and they live with the normal stresses of everyday American life.

What these groups do have in common, though, is a strong social infrastructure that ties people to each other emotionally and connects individual choices to a bigger community lifestyle.

It's hard to follow any diet when you're trying to do it on your own, in a culture that doesn't necessarily encourage you. It's hard to sleep in until 11:00 am every day (as the Ikarians do) when the social infrastructure of your community would actively punish such behavior. What's more, a common thread running through all these communities is an emphasis on the life-long pursuit of things that give your life meaning. There's not a cutoff point when you're expected to sit back, relax, and do nothing until you die.

The importance of systems, and how they shape individual behavior, is something I spent a lot of time thinking about while writing my book on energy. For example, it's somewhat futile to tell people to make an individual choice to drive less if the infrastructure of their city is set up in such a way that living without a car means being trapped in your house. But it's not something I'd thought about in terms of longevity.

Buettner's piece seems to suggest that it's not really your specific diet that matters. By which, I mean that eating healthy is definitely important, but there might not be a single, strict, specific diet that makes some things taboo and other things mandatory and must be followed at all times.

Instead, the important thing might really be your community as a system. If your community eats well (and makes eating well easy), so will you. If your community makes physical fitness part of daily life, you're more likely to be physically fit. If your community helps you create meaning in your life, it will be easier to find it. It's not really a solid answer for "HOW TO LIVE LONGER NOW", but it is intriguing. More importantly, from my perspective, it makes living a healthy life sound, you know, pleasant ... rather than like an obnoxious, individual dogma that creates smug insiders and resentful outsiders.

Of course, all of this fits nicely with my own personal biases, so who the hell knows. ;)

We do know from reliable data that people on Ikaria are outliving those on surrounding islands (a control group, of sorts). Samos, for instance, is just eight miles away. People there with the same genetic background eat yogurt, drink wine, breathe the same air, fish from the same sea as their neighbors on Ikaria. But people on Samos tend to live no longer than average Greeks. This is what makes the Ikarian formula so tantalizing.

If you pay careful attention to the way Ikarians have lived their lives, it appears that a dozen subtly powerful, mutually enhancing and pervasive factors are at work. It’s easy to get enough rest if no one else wakes up early and the village goes dead during afternoon naptime. It helps that the cheapest, most accessible foods are also the most healthful — and that your ancestors have spent centuries developing ways to make them taste good. It’s hard to get through the day in Ikaria without walking up 20 hills. You’re not likely to ever feel the existential pain of not belonging or even the simple stress of arriving late. Your community makes sure you’ll always have something to eat, but peer pressure will get you to contribute something too. You’re going to grow a garden, because that’s what your parents did, and that’s what your neighbors are doing. You’re less likely to be a victim of crime because everyone at once is a busybody and feels as if he’s being watched. At day’s end, you’ll share a cup of the seasonal herbal tea with your neighbor because that’s what he’s serving. Several glasses of wine may follow the tea, but you’ll drink them in the company of good friends. On Sunday, you’ll attend church, and you’ll fast before Orthodox feast days. Even if you’re antisocial, you’ll never be entirely alone. Your neighbors will cajole you out of your house for the village festival to eat your portion of goat meat.

Via Tom Rafferty

Read the full story at The New York Times Magazine

Hey guys! Check out this great JPEG I found last month. The caption was created by physics blogger Matthew Francis, and I've really been looking forward to sharing it with you!

In totally unrelated news, I just read a story by Stephanie Pappas at LiveScience.com, all about evolutionary psychologists' ongoing attempts to determine whether human females prefer our men hairy or smooth and, if so, why. Pappas' story covers a recent study that tried (and failed) to support one hypothesis: Women like hairless guys because we somehow know that hairy chests could be havens for parasites. A Sean Connery-like thatch is just one more place for lice to hang out.

Studying the preferences of women in two different cultures — Turkey and Slovakia — the researchers expected to find that Turkish women were more likely to choose hairless men because that country has long had higher rates of parasite-transmitted disease. Instead, they found that women in both countries overwhelmingly preferred their gentlemen in a less-wooly state.

The headline on the LiveScience article: "Why Women Don't Fall for Hairy Guys Remains A Scientific Mystery".

Time is relative. Remember how each day in grade school (especially summer days) seemed to last for an eternity? Ever notice how it seems to take forever to travel a new route on your bike, while the return trip along the same path is done in the blink of an eye?

Turns out, both of those things are connected and they have important implications for the nature of memory. There's a great summary of the science on this up at The Irish Times. It's written by William Reville, emeritus professor of biochemistry at University College Cork.

The key issue, according to Reville, is that the amount of information your brain can store during a given time period isn't really dependent on the length of that time period. You could store up a lot of new information during 10 minutes of a really interesting lecture. You might store only a little new information during 10 minutes of walking your dog along a path you know very well.

The higher the intensity, the longer the duration seems to be. In a classic experiment, participants were asked to memorise either a simple [a circle] or complex figure . Although the clock-time allocated to each task was identical, participants later estimated the duration of memorising the complex shape to be significantly longer than for the simple shape.

... [H]ere is a “guaranteed” way to lengthen your life. Childhood holidays seem to last forever, but as you grow older time seems to accelerate. “Time” is related to how much information you are taking in – information stretches time. A child’s day from 9am to 3.30pm is like a 20-hour day for an adult. Children experience many new things every day and time passes slowly, but as people get older they have fewer new experiences and time is less stretched by information. So, you can “lengthen” your life by minimising routine and making sure your life is full of new active experiences – travel to new places, take on new interests, and spend more time living in the present.

I think this also has some implications for my exercise routine. I am well aware that my ability to run any distance at all is heavily dependent on psychological factors. I am not one of those people who likes to go running in new places, along unfamiliar trails, because it has always made me feel like the distance was much, much longer — and, consequently, leads me to stop running and start walking sooner than I actually have to. I've had a lot more luck running on tracks and elliptical machines—situations where it seems to be easier for me to get into a zone and lose track of time. When I run that way, it's my physical limitations that matter, not my psychological ones.

Of course, I know a lot of people who feel exactly the opposite. Maybe, for those people, running in a routine situation, like a track, makes them start to think more about their day or what's going on around them, and processing all that information makes the workout seem longer. I'm not sure. But this is awfully interesting.

Read the rest of William Reville's piece at The Irish Times

Image: RUN Hills Pullover in action!, a Creative Commons Attribution (2.0) image from lululemonathletica's photostream

Over at the Scientific American blogs, science writer and biologist Rob Dunn talks about some of the theories for why something as seemingly antisocial as xenophobia could have been beneficial to our ancestors—at least under certain circumstances. The key, he says, might be disease. Not cooperating between groups, refusing to share resources, and generally going out of your way to avoid strangers makes sense if those strangers are infected with something that could kill you.

If I'm understanding Dunn correctly, the research and theorizing on this topic isn't saying xenophobia is good. Nor is it saying that all xenophobia grows out of a conscious, reasonable fear of disease. It's more like, the times when xenophobia did turn out to be coincidentally beneficial happened to reward people who were more likely to pass on xenophobic tendencies to their offspring (whether those tendencies were genetic or cultural is hard to say). Thus, the tendency continues, even in situations where it's actively detrimental. And Dunn points to an interesting recent study that showed deadly white-nose syndrome is causing xenophobic-esque changes in the behavior of bat populations.

Although it looked as though the little brown bats and several other species might soon face extinction, at least in some regions and perhaps even in North America, the little brown bats have begun to rebound in some places, albeit modestly. A new paper out this week takes notice of one of the reasons they appear to be rebounding, the bats are avoiding each other. Little brown bats (at least historically) tend to roost in large, groups, one next to the other, bumping fuzzies as it were. But not anymore. More and more, this new study, led by Kate Langwig, a graduate student at Boston University, suggests, the bats are spreading themselves out in their roosting caves, their hibernacula. Once, they clumped, warming themselves around the tiny fires of their bodies. Now, they go it alone.

Langwig’s results are preliminary, as she and her colleagues are the first to admit. She has measured the change in the bat roosting (and abundance) before and after the arrival of the disease, but she has not really studied the behavior of the bats and how it is they come to be spaced apart. Yet, the bats the are important from the perspective of the basic biology and conservation of the bats and so there remains much to do and much that can be done. For example, it would be good to know if the probability of transmission of the disease really goes down when the bats are further apart. It would also be interesting to figure out if the same individuals that were once nuzzling up next to each other, are now hanging out on their own.

Read the rest of Rob Dunn's post on xenophobia and disease

We've had a couple of posts recently about a hypothesis that links the current increase in obesity with an increase in easy access to foods that are designed to trigger reward systems in the human brain. Basically: Maybe we're getting fatter because our brains are seeking out the recurrent reward of food that makes us fat. Scientist Stephan Guyenet explained it all in more detail in a recent guest post.

It's an interesting—and increasingly popular—idea, though not without flaws. To give you some context on how scientists are talking about this, I linked you to a blog post by Scicurious, another scientist who wrote about some of the critiques of food reward and related ideas. In particular, Scicurious questioned some of the implicit connections being made here between body size and health, and eating patterns and body size.

She also talked about another critique, one which came up in a recent article in the journal Nature Reviews Neuroscience. If people are gaining weight because they're addicted to eating unhealthy foods, we ought to see some evidence of that in the way their brains respond to those foods. After all, brains respond to many physically addictive substances in special ways. But we don't see that with junk food. So does that invalidate the hypothesis?

Stephan Guyenet doesn't think it does. In a recent email to me, he explained that he thinks the food reward hypothesis is a bit more nuanced, and can't really be described as "food addiction". At least, not the same way that cigarettes or heroin are addictive.

Addiction is the dependence on a drug, or behavior, despite clear negative consequences. Drug addiction is associated with characteristic changes in the brain, particularly in regions that govern motivation and behavioral reinforcement (reward), which drive out-of-control drug seeking behaviors. Some researchers have proposed that common obesity is a type of “food addiction”, whereby drug addiction-like changes in the brain cause a loss of control over eating behavior. Hisham Ziauddeen and colleagues recently published an opinion piece in Nature Reviews Neuroscience reviewing the evidence related to this idea.

The review concluded that there is currently not enough evidence to treat obesity as a “food addiction”. I agree, and I doubt there ever will be enough evidence. However, this does not challenge the idea that food reward is involved in obesity, an idea I described in a review article in JCEM, on my blog (1, 2), and my recent Boing Boing piece.

The reward system is what motivates us to seek and consume food, and what motivates us to choose certain foods over others. To begin to appreciate its role in obesity, all we need is a common sense example.

Why do some people drink sweetened sodas between meals, rather than plain water? Is it because sodas quench thirst better than water? Is it because people are hungry and need the extra calories? If so, why not just eat a plain potato or a handful of unsalted nuts? The main reason people drink soda is that they enjoy it, plain and simple. They like the sweetness, they like the flavor, they like the feeling of carbonation on the tongue and the mild stimulation the caffeine provides. It’s the same reason people eat a thick slice of double chocolate cake even though they’re stuffed after a large meal. The reward system motivates you to seek the soda and cake, and the hedonic (pleasure) system encourages you to keep consuming it once you’ve begun.

But is this the same as addiction? If I took a person’s cola away, would they get the shakes? Would they break into a convenience store at night to get a cola fix? I’m going to say no.

I agree with Ziauddeen and colleagues that the evidence at this point is not sufficient to say that common obesity represents food addiction, and I appreciate their skeptical perspective on the matter. In obesity, as in leanness, the food reward system appears to be doing exactly what it evolved to do: seek out energy-dense, tasty food, and strongly suggest that you eat it. The problem is that we’re increasingly surrounded by easily accessible, cheap, commercial food that is designed to hit these circuits as hard as possible, with the goal of driving repeat purchase and consumption behaviors. Our brains are not malfunctioning; they’re reacting just as they’re supposed to around foods like this.

I've been doing periodic appearances on Sex is Fun, a sex-positive podcast aimed at providing fun, informative sex ed. for grown-ups. Last time I was on the show, we talked about some funny animal sex studies and what they can and can't teach you about human sexual behavior. This time around, we talked about a couple of recent studies focusing on sociology and sex.

In particular, we focused on a study from last fall that surveyed students at the University of Kansas to find out how men's and women's internalized sexism affect their relationships with each other. If you've ever watched one of those shows about so-called "pick up artists" and wondered, "Who the hell are the women falling for this crap!?", then this is the show to listen to.

Check out the podcast at the Sex is Fun site!

"My Favorite Museum Exhibit" is a series of posts aimed at giving BoingBoing readers a chance to show off their favorite exhibits and specimens, preferably from museums that might go overlooked in the tourism pantheon. I'll be featuring posts in this series all week. Want to see them all? Check out the archive post. I'll update the full list there every morning.

You've seen a lot of good taxidermy this week, but nothing quite like this. Renee Mertz sent me this photo of a diorama at Vienna's Naturhistorisches Museum, which depicts a group of butterflies greedily feeding off the carcass of a dead piranha.

This is not a spot of whimsy, people. This kind of thing really does happen. In fact, you can watch a real-life example (with a less-threatening fish substituted in for the piranha) in a video taken in Alabama's Bankhead National Forest.

The good news: The butterflies are not really carnivorous, per se. The bad news: What they're actually doing is still pretty damn creepy.

It's called "puddling" or "mud-puddling". The basic idea works like this: Butterflies get most of their diet in the form of nectar. They're pollinators. But nectar doesn't have all the nutrients and minerals butterflies need to survive, so they have to dip their probosces into some other food sources, as well. Depending on the species of butterfly, those other sources can include: Mineral-rich water in a shallow mud puddle, animal poop, and (yes) carrion.

When butterflies puddle over a dead fish, though, they aren't biting off chunks. Instead, they're essentially licking the dead fish—going after salt and minerals that seep out of the dead animal as it decomposes. Bonus: Some butterflies also like to lick the sweat off of humans. And a few species of moth have been documented sucking blood and tears for living animals, including humans.

This is simply breathtaking.

In the video, researchers pump 10 tons of concrete down an ant hole and then slowly, carefully excavate the site to see what an ant colony looks like. The result is an intricate structure, equivalent in labor to humans building the Great Wall of China.

And then you think, "Oh, and we just pumped 10 tons of concrete down it. Oh. We're ... kind of assholes sometimes, aren't we?" Sorry ants. Sants.

Here's a fascinating study that shines a bright spotlight of nuance on some of those maybe-too-simplistic assumptions we make about evolution, physical characteristics, and reproductive fitness.

If you've paid any attention to reporting on the science of what humans find attractive and why, you won't be surprised to learn that studies consistently show that deeper voices are associated with stereotypically manly-man characteristics such as hairier bodies and taller height, that men with these voices and characteristics are judged as being more attractive, and that deep-voiced dudes seem to get more action from more ladies.

Based on all of that, you might be tempted to speculate that a deeper voice is an outward sign of how fertile and virile a dude is and that ladies have evolved to be attracted to that show of baby-making prowess. And that makes sense ...

Except that men with deep voices also seem to have lower-quality sperm. At the Anthropology in Practice blog, Krystal D'Costa explains:

These assessments aren’t entirely made up. There is evidence that secondary sexual traits can predict health and fertility of a partner. Brilliant colors and showy displays have long been natural indicators of potential sexual fitness. For example, deer with bigger, more complex antlers also have larger testes and more motile sperm. Lower frequency sounds have been linked to larger body size across all primate species

However, semen analysis reveals that men with deeper voices have lower scores on seven motility parameters (7)—even when the lifestyle and environmental factors are accounted for. While men with deeper voices may have more sexual partners, they seem less prepared to pass on their genes. Researchers believe the lower sperm quality reflects a trade-off that comes with having to compete for mates:

“Animals have finite resources to partition amongst reproductive activities, and the theoretical models of sperm expenditure assume a basic trade-off between male investment in attracting mates and in gaining fertilizations. Recent studies of non-human animals are providing empirical evidence for this basic life-history trade-off. A number of studies have also reported short-term declines in semen quality associated with social dominance."

Perhaps you've heard the tale of the octopus that broke out of its tank at the aquarium and walked across the room to break into another tank where it proceeded to eat other forms of sea life.

That story is kind of an urban legend. It's supposedly happened at every aquarium in the world, but can't be confirmed. And experts have told me that the hard floors in an aquarium would likely seriously damage the suction pads of any octopus that tried it.

But the basic idea—that an octopus could pop out of the water and move across dry ground&dmdash;is a very real thing. Here, an octopus at the Fitzgerald Marine Reserve in California hauls itself out of the water, and scoots awkwardly around on land for a little bit (while some apparently Minnesotan tourists gawk), before sliding back into the water. It's not the most graceful sort of travel. But it can be very handy. Octopuses do this in nature to escape predators, and also to find food of their own in tidal pools.

As an added bonus: Scientific American just started an all-octopuses, all-the-time blog called The Octopus Chronicles. Check it out!

Video Link

Bones can tell you a lot about a creature, but there's much more they can't tell you. Bones are not behavior. We know what the skeletons of dinosaurs looked like. But there's a great deal about their appearance and behavior that we can only guess at.

Sometimes, though, bones can surprise you. Sometimes, they carry secrets locked inside. At Not Exactly Rocket Science, Ed Yong writes about a new study that's uncovered evidence about dinosaur behavior, using information stored in the dinosaurs' teeth. The paper suggests that the North American Camarasaurus had a seasonal migration.

Reptiles replace their teeth throughout their lives and the dinosaurs would have been no different. Whenever they drank, they incorporated oxygen atoms from the water into the enamel of their growing teeth. Different bodies of water contain different mixes of oxygen isotopes, and the dinosaurs’ enamel records a history of these blends. They were what they drank.

It’s easy enough to measure the levels of oxygen isotopes in dinosaur teeth, but you need something to compare that against. How could anyone possibly discern the levels of such isotopes in bodies of water that existed millions of years ago? Local rocks provide the answer. The oxygen also fuelled the growth of minerals like calcium carbonate (limestone), which preserve these ancient atoms just as dinosaur teeth do. If dinosaur enamel contains a different blend of oxygen to the surrounding carbonates, the place where the animal drank must be somewhere different from the place where it died.

Palaeontologists have used oxygen isotopes to infer all manner of dinosaur traits, from the fish-eating habits of spinosaurs to the hot body temperatures of sauropods to the chilly conditions endured by Chinese dinosaurs. These atoms have acted as menus and thermometers. Now, Fricke has turned them into maps.

My friend Jim captured this excellent moment in science reporting this morning. Thankfully, as I check Google News now, the headlines are drifting more towards the real story, which is fairly interesting. Turns out, deadly car accidents aren't so much a function of driver age as they are a function of driver experience.

Basically, over the past few decades, several states have placed stringent limits on teenage drivers—usually when they can drive, and who they can drive with. The idea was to separate first-time drivers from risky driving situations, and a lot of people assumed these measures were saving lives. Instead, we now know, the rules merely shifted when the deadly accidents happened. Some lives were saved. But, in general, the results were pretty much a wash.

The researchers found that states with the most restrictive graduated licensing programs — such as those that required supervised driving time as well as having night-driving restrictions and passenger limitations — saw a 26% reduction in the rate of fatal crashes involving 16-year-old drivers compared with states without any restrictions.

But the rate of fatal crashes among 18-year-old drivers in those states jumped 12% compared with the states without restrictions.

A similar trend was seen when comparing drivers in states with strong graduated licensing programs with those in states with weak programs: The rate of fatal crashes among 16-year-old drivers was 16% lower but was 10% higher among 18-year-old drivers.

Overall, since the first program was enacted in 1996, graduated programs were linked to 1,348 fewer fatal crashes involving 16-year-old drivers and 1,086 more fatal crashes involving 18-year-old drivers.

The speculative response: You can place restrictions on new drivers that limit their exposure to situations where mistakes are likely to happen. But, eventually, they'll have to navigate those situations on their own. And when they do, the mistakes creep back in. So maybe we need to look for a better way to mitigate the mistakes than simply instituting age-dependent restrictions. Personally, I wonder what the results would be if driving education included time to practice driving (either virtually or on a test course) with the distractions they're likely to encounter in real life. I know I learned how to drive and talk at the same time, and how to know when to shut everybody up, by experience. Maybe there's a way to do that in a safer environment.

Wow.

That comes from Jason Goldman, a scientist and science blogger, who has a post up today about how animals that thrive in extreme heat situations actually manage to do that. Specifically, he's writing about a recent paper that studied how harsh environments change the parenting behavior of desert birds. Apparently, the hotter the nest, the more the male bird is likely to be involved in incubating the eggs.

Biparental care, which is the care of offspring by both male and female parents, represents a classic example of the trade-off between cooperation and conflict in social behavior in the animal kingdom. If they cooperate, parents can work to improve the odds of the survival of their offspring. By withholding care, however, an individual can potentially survive longer and increase the odds of successful breeding later in life. Assuming that biparental care is even possible in a given species, mathematical models expect it to occur anytime the possibility of offspring survival is significantly greater than when cared for by a single parent. In particular, the harsh environment hypothesis predicts that parents should both contribute to the care of their young in environments susceptible to harsh weather conditions, where food is scarce, where there is intense competition for resources, if desiccation of eggs is a possibility, or in areas where the offspring are regularly preyed upon.

The Kentish plover provided Al-Rashidi with the opportunity to conduct a particularly clever experiment. These birds lay their eggs on the ground, which means that the eggs as well as both parents have direct exposure to the surrounding environment. Some nests are located under bushes, and are therefore naturally protected from direct sunlight, while others are out in the open. This provided an obvious way for Al-Rashidi to create two experimental groups – one in direct sunlight and a second in the shade. In general, males tend to sit on the nest during the cooler nighttime, while females tend to take the daytime shift. The problem is that the females risk overheating if they incubate the eggs all day. The harsh environment hypothesis, therefore, predicts that the warmest nests will not only show evidence of more biparental care but that the two parents will take turns more often throughout the day.

... As expected, males and females both spent more time sitting on the exposed nests than the covered ones over the whole day, and as predicted by the harsh environment hypothesis, there were more change-overs – that is, they took turns more often – during the hottest part of the day at the exposed nests.