Why do humans have so little hair, at least compared to all other primates? At Smithsonian, Jason Daley shares the latest genetic research on the biological factors that result in humans' minimal body hair and its unusual distribution. Daley also surveys the fascinating current theories about why we evolved into the only naked apes. From Smithsonian:

One popular idea that has gone in and out of favor since it was proposed is called the aquatic ape theory. The hypothesis suggests that human ancestors lived on the savannahs of Africa, gathering and hunting prey. But during the dry season, they would move to oases and lakesides and wade into shallow waters to collect aquatic tubers, shellfish or other food sources. The hypothesis suggests that, since hair is not a very good insulator in water, our species traded in most of our fur for a layer of fat. The hypothesis even suggests we might have developed bipedalism to become more effective waders. But this idea, which has been around for decades, hasn’t received much support from the fossil record and isn’t taken seriously by most researchers.

A more widely accepted theory is that, when human ancestors moved from the cool shady forests into the savannah, they needed better thermoregulation. Losing all that fur made it possible for hominins to hunt during the day in the hot grasslands without overheating. An increase in sweat glands, many more than other primates, also kept early humans on the cool side. The development of fire and clothing meant that humans could keep cool during the day and cozy up at night.

The PainStation is a cocktail-style Pong game that provides "sensory feedback" to players. Which is to say: pain. Physical pain.

During the game, the players place their left hands on the PEU (Pain Execution Unit) which serves as a sensor and feedback instrument. Possible feedback effects are heat impulses, an electric shock and an integrated miniature wire whip. The feedback generated is dependent on the playing process and can increase in its intensity. The respective opponent can try to alter his or her playing style to purposely change the intensity of the feedback.

Painstation is also remarkable in the degree of refinement applied to the basic Pong concept: ball speed, ricochet characteristics, bar length, etc, are all variable and under the influence of bonuses and competitive machinations. But it is the pain bonuses that matter:

Double Pain Execution Time Quadruple Pain Execution Time Death Penalty Ease the Pain!

Photo: Ultimaratiopharm Read the rest

The family of Henrietta Lacks — a woman whose cervical cancer cells were harvested and used in scientific research for decades without her knowledge or consent — will now play a role in deciding who has access to the Lacks' cell genome data, and for what purposes. There are loopholes in the new system. For instance, the agreement only applies to scientists who receive National Institutes of Health funding. And the genome of the cells has been sequenced so many times, at this point, that anybody who wasn't NIH funded and didn't want to voluntarily abide by the agreement essentially wouldn't have to.

But it is a big step forward, both for the Lacks family (whose own genetic information is contained in those genome sequences) and for the idea that human genetic information belongs to the people it comes from — not to whoever happens to sequence it.

The happy selfie posted here features NIH director Francis Collins posing with some of Henrietta Lacks' descendants after the agreement was announced. Read the rest

More than a quarter of primate species form male-female pair bonds that scientists describe as "monogamous". That's much higher than the overall mammal average of 9 percent. But those statistics don't mean that humans are somehow "meant" to be monogamous. In fact, scientists are still debating — and publishing conflicting theories — on why monogamy would have evolved at all. Carl Zimmer has an interesting column at The New York Times looking at two recent papers, and how they fit into an ongoing scientific fascination with our own sex lives. Read the rest

In Tulsa, Oklahoma, over the last 30 years, the number of cliff swallows killed by moving vehicles has drastically decreased. That change can't be accounted for by alterations in traffic patterns or swallow populations, say scientists. Instead, they think it's tied to the fact that the birds' wingspan is also decreasing. This adaptation — whether selected for by vehicular birdicide and/or other factors — helps swallows be more nimble in the air at high speeds, making it easier for them to avoid oncoming traffic. (EDIT: Sorry guys, I made an error here. Some of the researchers were from Tulsa, but study actually happened in Nebraska. Evolution takes place throughout the plains states.) Read the rest

There is definitely a seasonality to human births, writes Beth Skwarecki at Double X Science. The complicated bit is that human baby season isn't necessarily the same (or as strongly expressed) from place to place and culture to culture. In the United States, significantly more babies are born in July, August, and September. Meanwhile, in Europe, babies seem to make their way into the world in spring. So there's clearly a cultural component to this — but culture doesn't explain it, entirely. Skwarecki's piece explores a messy place where culture, genetics, and circadian rhythms intersect. Read the rest

On the left is a picture of me with my bike, taken by my friend Laura Kling. On the right is the same image, as it would be seen by a person with protanopia — a relatively common (as in, still very rare) form of color blindness that affects the ability to see green, yellow, and red colors.

The Color Blindness Simulator will allow you to do this with your own photos. Read the rest

According to a new book, the human overbite developed at different times, in different places — and was always coincident with the widespread use of eating utensils. In Europe, for instance, evidence suggests that humans have only had an overbite for about 250 years. Read the rest

I really enjoyed reading a recent story in The New York Times Magazine about attempts to understand extreme longevity — the weird tendency for certain populations to have larger-than-average numbers of people who live well into their 90s, if not 100s.

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. Read the rest

In an interview with The Houston Chronicle, paleoanthropologist Jean-Jacques Hublin hits on an interesting point that I don't think we (the media and laypeople) consider enough when we talk about our closest ancient relatives. Although we have an increasingly deep picture of Neanderthal anatomy and genetics, that doesn't necessarily tell us a great deal about their biology.

Truth is, for how little we understand the wiring and functioning of our own brains, we understand even less about the Neanderthal mind. It's quite possible that they could mate with us, but couldn't think the same way we do. And it's those unseen, unstudied differences that could really account for the vast disparities that we see between how humans lived and how their Neanderthal neighbors lived.

The picture we have so far is that the Neanderthals are sort of opportunistic, good at hunting middle- to large-sized mammals. They have a territory in which they probably go through a cycle of habitation in different places, basically when one place is exhausted they move to another one. What we don't see with Neanderthals is long-distance exchanges with other groups. What we see with modern humans in the same areas is different. For example, we find shells in Germany coming from the Mediterranean or from the French Atlantic Coast. It means there was a network of people. So, the question is, what kind of relationship did a Neanderthal have with his brother-in-law? Humans did not just live with their families and their neighbors, but they knew they had a brother-in-law in another village, and that beyond the mountain there is the family of their mother, or uncle, or something like that.

By now, many of you are probably aware that human behavior is one of the key factors behind some of the massive forest fires we've seen in recent years. The basic story goes like this: Under a natural cycle, periodic small fires sweep through forests, burning through small trees and dry brush. But if you prevent those fires from happening—as humans have done for around a century at this point—all that highly flammable stuff builds up. In the end, you're left with a giant tinderbox of a forest. The next time a fire does happen there, it's almost guaranteed to be much, much bigger and more destructive than the natural fires that forest is adapted to.

NPR has a very nice story about the science and history behind this problem, which forest fire experts call "The Smokey Bear Effect", after the cartoon Ursus the U.S. Forest Service has long used as part of its fire prevention campaign.

Its ill-advised fire prevention campaign.

And it was the experts who approved the all-out ban on fires in the Southwest. They got it wrong. That's the view of fire historian Stephen Pyne.

"The irony here is that the argument for setting these areas aside as national forests and parks was, to a large extent, to protect them from fire," Pyne says. "Instead, over time they became the major habitat for free-burning fire."

So instead of a few dozen trees per acre, the Southwestern mountains of New Mexico, Arizona, Colorado and Utah are now choked with trees of all sizes, and grass and shrubs.

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.

Given the trend lately to look backwards, historically, in search of the ideal human diet, I found this article by Rob Dunn really interesting. Dunn discusses some new research that gives us a better idea of what our closest relatives—chimpanzees and bonobos—are eating out in the wild.

Some of the takeaways fit neatly into the current human food zeitgeist—chimpanzees eat a diverse and varied diet, only consume small amounts of meat, and (for obvious reasons) focus on what happens to be in season and available. But some of the information is less apparently applicable to us. For instance, chimpanzees fracking love figs. In fact, different species of figs make up nearly half of all the food the chimpanzees in the study were eating. Figs, people. Can't get enough of 'em.

But the larger point, Dunn writes, is that we can't really apply any of the facts about chimpanzee diets directly to ourselves in a "Just So Story" sort of way. Geography, resource availability, and culture don't work like that. Neither does biology.

You are unlikely to eat like a chimpanzee eats. If you are the average American, you eat more meat and more simple sugar. You eat differently because of choices you make and choices our societies have made (e.g., to produce huge quantities of the foods that most simply satisfy our ancient urges). You also eat differently because the species around you are different, unless you happen to own a greenhouse specializing in tropical African trees.

But even if you were to abandon agricultural food and move into a forest in Tanzania you would still not eat exactly like a chimpanzee.

In 2005, my husband I bought a house in Birmingham, Alabama. I was working for mental_floss and we thought we'd live there for a few years. But, in 2006, my husband got an amazing job opportunity in Minneapolis. So we moved and we sold our house. After a few months in the Twin Cities, we bought another one. In order for me to buy the house I now live in, somebody else had to move. When I left my house in Birmingham, I opened a spot in my neighborhood there that was filled by somebody else.

This is one of those things that seems so basic and "duh" that it's easy to overlook. It's easy to think that it isn't important. But sociologists, and economists, care a lot about these patterns—called vacancy chains. That's because vacancy chains end up describing very similar situations that occur in all sorts of social systems across many, many species.

When a resource is exchanged in a sequence from one individual to another, and every individual in the sequence benefits from the exchange, that's a vacancy chain. You see these patterns in human home sales—I, the people I bought my house from, and the people who bought my old house all ended up with a home that better met our needs. And you see the same thing when hermit crabs trade out their old shells for new ones.

Ivan Chase, emeritus professor at Stony Brook University, studies vacancy chains in hermit crabs and people. He's written about his work for the June issue of Scientific American, and he recently spoke with me about how vacancy chains work and what we can learn about human social systems from watching animals like crabs. Read the rest

Today, we're the only living member of the genus Homo and the only living member of the subtribe Hominina. Along with chimpanzees and bonobos, we're all that remains of the tribe Hominini.

But the fossil record tells us that wasn't always the case. There were, for instance, at least eight other species of Homo running around this planet at one time. So what happened to them? What makes us so special that we're still here? And isn't it just a little weird and meta to be fretting about this? I mean, do lions and tigers spend a lot of time pondering the fate of the Smilodon?

Today, starting at 12:00 Eastern, you can watch as a panel of scientists tackle these and other questions. "Why We Prevailed" is part of the World Science Festival and features anthropologist Alison Brooks, genome biologist Ed Green, paleoanthropologist Chris Stringer (one of the key researchers behind the "Out of Africa" theory), and renowned evolutionary biologist Edward O. Wilson.

You can also join in a live conversation about the panel, which I'll be hosting. Just post to Twitter with hashtag #prevail, or join us at UStream. Read the rest

The Leakey family is like the Kennedys, but for paleoanthropology instead of politics. Think about any hominin fossil or artifact you can name. Chances are, there was a Leakey involved in its discovery. Louis Leakey was one of the first scientists to champion the idea that humans had their origins in Africa. For three generations now, his family has carried out active paleo excavations in eastern Africa, especially the countries of Tanzania and Kenya.

The first generation—Louis Leakey and his wife Mary—were most associated with Tanzania's Oldupai Gorge. But their son Richard, his wife Meave, and their daughter Louise have all spent their careers focused on Lake Turkana, on the border between Kenya and Ethiopia. The site is the world's largest, permanent desert lake. Undisturbed by modern development, in a spot where millions of years of flowing water have washed deposits and fossils down from the rift valley—Lake Turkana is an excellent place to search for human ancestors and our ancient relatives.

On Wednesday, PBS will air an hour-long documentary on the Leakeys' work at Lake Turkana. Part biography of Richard Leakey and part exploration of human history—Bones of Turkana will air May 16th at 9:00 pm central and again on May 21st at the same time. Yesterday, I got the opportunity to speak with Richard and Meave Leakey. We talked about human evolution, the scientific promise of Lake Turkana, the process of paleo fieldwork, and the lasting impression of the Leakey legacy. Read the rest

Over the weekend, at the Earth Day tweetup at the Science Museum of Minnesota, I heard an interesting fact: Human beings are now the dominant agent of landscape change on this planet, more than any natural process. (That's right. Suck it, glaciers!)

We tend to think of this kind of thing as a result of modernity. But I think that's only partly true. Modern technology has given us the tools that enable us to change the landscape of Earth in massive ways we weren't capable of in the past. But throughout human existence—even before we were technically human—we have made relatively large alterations to the world. It's not like human beings woke up one day and thought, "Hey, it's the 20th century, let's start messing around with stuff!" In reality, what makes our modern impact on the planet different from past—other than scale—is mainly that we've developed more self-awareness about our impact on the planet, and have actually started talking about whether we like the side effects those impacts bring.

Case in point: A recent study of ancient African animal species that suggests our ancestors drove a huge proportion of fauna to extinction basically as soon as they were technologically capable of doing so. Here's how Ann Gibbons described it at Science Now:

After comparing fossils of 78 species of carnivores that lived during five different periods of time between 3.5 million years ago (when large carnivores were at their peak) and 1.5 million years ago, Werdelin found that all but six of 29 species of large carnivores (animals that weighed more than 21.5