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.
"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!
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.
So here's a statistic I'd never heard before: Between 1979 and 2003 years, more Americans died from heat exposure than from hurricanes, lightning, tornadoes, floods, and earthquakes combined.
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.