It seems like such a simple question, but it's actually one of the most biggest mysteries in all of science. Is it because of how our brains are organized, how ancient humans gripped tools, or is it simple anti-lefty prejudice?

Nobody knows for sure, but scientists have come up with theories that are alternately intriguing, persuasive, and a little bonkers. Let's take a look at the often baffling science of handedness, running from how the development of language in early humans might have helped cause the evolution of handedness...to how all the world's languages seem to have it in for lefties.

Why does handedness exist?

Handedness - the idea that one hand is better able to perform certain tasks than the other - is, if not exclusively a human trait, then certainly a mostly human one. After all, how could you tell if a dog was left-handed or a lion was right-handed? Their paws aren't evolved to handle complex tasks like our hands are, and there's no evidence that non-primates favor one limb over any other.

But exactly why humans favor different hands, or why most people tend to be right-handed, remains mysterious. The most common answer is that handedness is determined by the structure of our brains, which are divided into two hemispheres. Our brains are far more specialized than those of other animals, with different regions of the brain responsible for different specific tasks. Admittedly, these are only general guidelines, and most neural activities are shared between the hemispheres to some extent, but we can definitely say that many functions are primarily handled by one hemisphere as opposed to another. This is known as brain lateralization.

Two of the most energy-intensive human activities are language and the use of our fine motor skills - in other words, the use of our hands. One theory suggests that it's more efficient for the brain to cluster control of these two major tasks in one hemisphere rather than having it spread throughout the brain. Since the vast majority of people have their language functions centered in the left hemisphere, it follows that most people's fine motor skills would be controlled by the left hemisphere too. Each hemisphere generally controls the opposite side of the body, so the end result is that most people are right-handed.

However, the opposite does not hold true - being left-handed does not mean the language centers are located in the right hemisphere, which is fairly rare. Certainly, lefties are more likely than righties to have their right hemisphere responsible for language, but it's still not a common arrangement. Between 61 and 73% of lefties have their language centers in the left hemisphere, compared to over 90% of right-handed people.

This doesn't necessarily invalidate the division of labor theory. After all, between 70 and 90% of people are right-handed, and well over 90% of those people do indeed cluster language and fine motor skill control in the left hemisphere. What we're looking at here is the evolutionary equivalent of a rule of thumb. People's brains are generally organized to maximize energy efficiency, but a reasonably large minority of people - including most lefties - get along just fine with a less efficient arrangement.

But why are most people right-handed?

As we've discussed, another possible way of phrasing that is, "Why is the language center usually in the left hemisphere of the brain?" After all, if the energy intensive language centers happened to evolve so that they were usually in the right hemisphere, then most people would probably be left-handed instead. To that point, there's no reason why our brains couldn't have evolved that way - it's simply a historical fact that they didn't.

But that hasn't stopped scientists from attaching great significance to the fact that we evolved as righties instead of lefties. In the January 1, 2002 issue of Discover Magazine, Jocelyn Selim describes a particularly spectacular theory:

In most primates and other animals, the hemispheres of the brain divide the processing of tasks somewhat equally. But in humans, the hemispheres tend to specialize: Nearly all righties process language in the left side of the brain, while many lefties process language on the right. Because handedness and language both seemed uniquely human traits, biologists long assumed that they were closely linked.

One Oxford neurobiologist went so far as to argue that right-handedness could be traced back 200,000 years to a single mutation-a sort of genetic Big Bang that created hemispheric specialization, language, and higher cognitive functioning in one go. Right-handedness, to this way of thinking, is the most obvious mark of the genetic instructions that separate us from speechless, symmetric beasts.

While some of that that might be going a bit far - if nothing else, it doesn't seem to leave a lot of room for lefties - the root of handedness quite possibly is a random genetic mutation that pushed the language centers to the left hemisphere as the ancient human brain became more specialized. Without this particular genetic mutation, our brains still might have evolved to their present levels of sophistication, but our language hemispheres would be chosen at random, meaning handedness would be more evenly split.

In fact, a second major gene mutation might have had precisely that effect, at least in a subset of the population. University College London neuropsychologist Chris McManus suggests that sometime between 20,000 and 100,000 years ago, a second mutation entered the human gene pool that canceled out the brain's natural bias towards right-handedness, allowing for the emergence of more left-handers. People who carry this second mutation are also more likely to have unusual patterns of brain organization, which neatly explains why lefties are more to have both high intelligence and mental disorders.

So is it really all about language?

Well...that's just one theory. It's a pretty good one, as theories go, but it doesn't explain everything, and - as we've just seen - it very easily gets wrapped up in grand triumphal stories of humanity's brilliant evolution. Certainly, we should be careful in saying the development of language centers in the left hemisphere caused the rise of handedness. The two appear linked, but it may not be quite as direct as we might have imagined.

One issue is that we're not the only other animals to use a particular hemisphere of the brain to create noises. Birds and frogs, for instance, process the noises they make in one particular side of the brain, and there's no evidence of handedness in the way they use their limbs. University of Auckland researcher Michael Corballis suggests an alternative explanation for our handedness in the Discover article:

"It's quite possible that what set humans apart was that speech began from gestures, which would explain an indirect association with handedness. But it's one of those mysteries that refuses to resolve itself. Think of it this way: Primates do have very symmetrical brains, but then again, so did Einstein."

The division of labor theory and the two genetic mutations don't need to be thrown out - instead, we can roll them into a larger picture of the evolution of handedness. It's possible that the specialization of our brains were already pushing our species toward handedness, but this process was accelerated by the activities of ancient humans, in particular their use of tools. In a 2009 blog entry for Science, Michael Balter details one possible explanation for the rise of handedness:

The "technology-dense lifestyles" of early hominins might have required our ancestors to more or less make up their minds about what hands they were going to use to perform complex tasks. Moreover, such hand bias could have aided the learning process as hominins taught each other toolmaking and other skills; a number of studies have shown that people learn manually difficult tasks, such as knot-tying, more easily when they use the same left- and right-hand movements as their teachers.

We can also add into the mix the development of longstanding, pervasive social prejudices against left-handedness, which I'll discuss in more detail in a little bit. These prejudices likely influenced countless children who otherwise would have developed into lefties to essentially force themselves to be right-handed, effectively inflating the proportion of the right-handed population.

When did handedness first evolve?

We can feel reasonably confident that Neanderthals and Homo heidelbergensis were right-handed. Neanderthal skeletons tend to have stronger right arms and shoulders than their left counterparts, perhaps because they used them to throw spears while hunting animals. There's less direct evidence for Heidelbergensis, but we can tell from their preserved teeth indicate that they ate food with their right hands. The 1.6 million year old Homo ergaster skeleton Nariokotome Boy showed signs of right-handedness, but we can't infer the hand preference of an entire species from just one skeleton.

Determining the handedness of other primates is also tricky for a bunch of reasons. In general, wild primates aren't particularly likely to engage in the sorts of activities that require fine motor skills - and thus would require handedness - and it's hard to know whether we can really trust results we get from giving human-like tasks to captive primates. But as primatologist Bill Hopkins explains in the Discover article, decades of accumulated research have given us some rather unexpected answers:

A close look at primate research since the 1920s shows that all primates have hand preferences, and those preferences follow a clear pattern: Lemurs and other prosimians tend to be left-handed; macaques and other old-world monkeys are evenly split between lefties and righties; among gorillas and chimpanzees, 35 percent are lefties, while in humans that percentage hovers around 10. In other words, the more primitive the primate, the more likely it is to be a lefty. Left-handedness, far from being a recent invention, seems to predate right-handedness.

We know that the ancestor of all primates evolved about 65 to 85 million years ago as a member of the extinct order Plesiadapiformes. One of the last of the Plesiadapiformes was Carpolestes simpsoni, which had grasping digits like those of all its primate descendants. It's possible that the development of handedness goes right back to this very ancient transition from claws to digits.

Why primates apparently slowly moved from left-dominant to right-dominant as they evolved remains an open question. We could go back to the division of labor theory here. It's possible that because Carpolestes simpsoni and the earliest primates had small brains, they had to cluster control of their emerging motor skills in one hemisphere, which just happened to be the right.

This led to a lot of left-handed monkeys, but as larger, bigger-brained primates began to evolve, this division of labor became less important, which opened the door for a wider mix of righties and lefties. Of course, that doesn't explain why handedness started to swing towards righties as we get to chimps and gorillas is still - it's certainly possible that changing brain structure and random mutations played a major role, but we just don't know for sure.

What does it actually mean to be right-handed or left-handed?

After everything we've already discussed, that may seem likely a stupidly easy question, but it's surprisingly controversial. The everyday answer to that question is probably this: if you write with your right hand, then you're right-handed. It's a straightforward enough popular definition, but translating that into scientific terminology is trickier than you might think. Even simply saying that handedness is determined by which hand you prefer to use doesn't actually help us that much.

Let's consider some of the problems here. Should a person's dominant hand be determined by the hand they prefer to use, or the hand that performs better in tests? In other words, is handedness primarily psychological or physiological? Even if you can sort that out, there's still the question of how to categorize all this. Should left-handed and right-handed be considered precisely equal, or does the fact that such a vast majority of people are right-handed suggest that the people are simply either right or non-right? That's a bit of a charged way to look at things, but it does have some popularity in scientific literature.

And how about people who use different hands for different tasks? I write and throw with my right hand but bat and play(ed) hockey with my left hand - should I be considered primarily right-handed, a mix of right- and left-handed, or ambidextrous, meaning I feel equally comfortable using both hands? (Yeah...I'm probably not ambidextrous.) And should we look at handedness as something that can be lumped into only a very few categories - say true right-handed, more right-handed, ambidextrous/mix, more left-handed, and true left-handed - or something that exists on a broad spectrum?

Indeed, the very idea that one hand is "dominant" might be a complete misunderstanding of how our hands divide up tasks. In the Science post, Michael Balter details an argument by University of Liverpool archaeologist Natalie Uomini:

Uomini points out that handedness does not mean that one hand is "dominant" over the other. Rather, she writes, "both hands have different but equally important roles." In right-handed people, for example, the right hand might be used for tasks requiring greater manual dexterity whereas the left hand might perform the more mundane but nevertheless crucial role of supporting an object. (Imagine eating dinner with just a knife but no fork, for example.)

There isn't a ton of consensus here - ask a dozen scientists and you'll probably get at least ten different ways to define and organize handedness. Part of the problem here is that handedness is generally a pretty touchy issue, one with a long history of bias and prejudice. Speaking of which...

What exactly do people have against lefties?

For reasons that can probably best be described as "stupid", people have historically held left-handers in contempt. You can find evidence of an anti-left bias throughout the world's languages. The word "left" itself comes from the Anglo-Saxon word "lyft", which means "weak." We get the word "sinister" from the Latin word for "left", and that double meaning persists in the modern Romance languages.

It really is an insanely long list - English, French, Chinese, Korean, Finnish, Irish, Hungarian, Dutch, Spanish, Italian, Portuguese, German, and most of the Slavic languages all either link the word "right" with goodness, the word "left" with wrongness and impropriety, or both. That's not even getting into all the expressions and customs that have sprung up against left-handed people. In Ghana, even gesturing with the left hand can be considered taboo, and a common form of 19th century bigotry was to say minority groups such as homosexuals and Roman Catholics were left-handed.

As to why these prejudices exist - well, it does appear that majority right-handedness has been around at least since modern humans first emerged 200,000 years ago. This may simply be a case of a natural majority picking on a minority, perhaps out of an embarrassingly human fear of what's different. There's also at least one possible vaguely practical reason for this animosity. As any lefty will be happy to tell you, tons of everyday objects that right-handed people take for granted are a pain in the ass to use if you're a lefty. There's spiral notebooks, can-openers, stick shifts...and that's just what I remember from the Simpsons episode on the subject.

It's possible that ancient tools were similarly designed with right-handed users in mind, and the natural difficulties a lefty would have with such implements could draw social scorn and, over time, build up negative associations towards lefties. That all sounds fairly fanciful, honestly - although a few languages do have words that mean both "left" and "clumsy", suggesting a linked meaning somewhere along the line. Ultimately, we're probably just looking at good old-fashioned fear of the unusual.

There's really no definitive evidence either way that righties are better than lefties or vice versa - they just happen to hold their pencils differently. And while there have been a bunch of attempts to tease out specific differences between the two groups - including a recent study that basically suggested left-handedness is a form of cognitive impairment - there's way too much conflicting data out there to say much for certain.

As Chris McManus observed in the Discover article, ""The real question is why everyone wants left-handers to be defective", and there's a great deal of truth to that observation both throughout history and right up to now. Anyway, if this whole exercise has taught us anything, it's that we're probably just a couple random genetic mutations away from left-handers snootily trying to figure out what's up with that 30% minority of righties.

Further Reading

Is being left-handed a form of cognitive impairment? by Alasdair Wilkins
The Biology of Handedness by Jocelyn Selim
The Origins of Handedness by Michael Balter
What does Handedness have to do with Brain Lateralization (and who cares?) by M.K. Holder
Wild chimpanzees show population-level handedness for tool use by Elizabeth V. Londsor and William D. Hopkins

Image Credits

Top image by M.C. Escher.
Cerebral lobes via Wikimedia.
Green frog by thatredhead4 on Flickr.
Carpolestes simpsoni by Sisyphos23 on Wikimedia.
Leftorium via Loonpond.

It seems like such a simple question, but it's actually one of the most biggest mysteries in all of science. Is it because of how our brains are organized, how ancient humans gripped tools, or is it simple anti-lefty prejudice?

Nobody knows for sure, but scientists have come up with theories that are alternately intriguing, persuasive, and a little bonkers. Let's take a look at the often baffling science of handedness, running from how the development of language in early humans might have helped cause the evolution of handedness...to how all the world's languages seem to have it in for lefties.

Why does handedness exist?

Handedness - the idea that one hand is better able to perform certain tasks than the other - is, if not exclusively a human trait, then certainly a mostly human one. After all, how could you tell if a dog was left-handed or a lion was right-handed? Their paws aren't evolved to handle complex tasks like our hands are, and there's no evidence that non-primates favor one limb over any other.

But exactly why humans favor different hands, or why most people tend to be right-handed, remains mysterious. The most common answer is that handedness is determined by the structure of our brains, which are divided into two hemispheres. Our brains are far more specialized than those of other animals, with different regions of the brain responsible for different specific tasks. Admittedly, these are only general guidelines, and most neural activities are shared between the hemispheres to some extent, but we can definitely say that many functions are primarily handled by one hemisphere as opposed to another. This is known as brain lateralization.

Two of the most energy-intensive human activities are language and the use of our fine motor skills - in other words, the use of our hands. One theory suggests that it's more efficient for the brain to cluster control of these two major tasks in one hemisphere rather than having it spread throughout the brain. Since the vast majority of people have their language functions centered in the left hemisphere, it follows that most people's fine motor skills would be controlled by the left hemisphere too. Each hemisphere generally controls the opposite side of the body, so the end result is that most people are right-handed.

However, the opposite does not hold true - being left-handed does not mean the language centers are located in the right hemisphere, which is fairly rare. Certainly, lefties are more likely than righties to have their right hemisphere responsible for language, but it's still not a common arrangement. Between 61 and 73% of lefties have their language centers in the left hemisphere, compared to over 90% of right-handed people.

This doesn't necessarily invalidate the division of labor theory. After all, between 70 and 90% of people are right-handed, and well over 90% of those people do indeed cluster language and fine motor skill control in the left hemisphere. What we're looking at here is the evolutionary equivalent of a rule of thumb. People's brains are generally organized to maximize energy efficiency, but a reasonably large minority of people - including most lefties - get along just fine with a less efficient arrangement.

But why are most people right-handed?

As we've discussed, another possible way of phrasing that is, "Why is the language center usually in the left hemisphere of the brain?" After all, if the energy intensive language centers happened to evolve so that they were usually in the right hemisphere, then most people would probably be left-handed instead. To that point, there's no reason why our brains couldn't have evolved that way - it's simply a historical fact that they didn't.

But that hasn't stopped scientists from attaching great significance to the fact that we evolved as righties instead of lefties. In the January 1, 2002 issue of Discover Magazine, Jocelyn Selim describes a particularly spectacular theory:

In most primates and other animals, the hemispheres of the brain divide the processing of tasks somewhat equally. But in humans, the hemispheres tend to specialize: Nearly all righties process language in the left side of the brain, while many lefties process language on the right. Because handedness and language both seemed uniquely human traits, biologists long assumed that they were closely linked.

One Oxford neurobiologist went so far as to argue that right-handedness could be traced back 200,000 years to a single mutation-a sort of genetic Big Bang that created hemispheric specialization, language, and higher cognitive functioning in one go. Right-handedness, to this way of thinking, is the most obvious mark of the genetic instructions that separate us from speechless, symmetric beasts.

While some of that that might be going a bit far - if nothing else, it doesn't seem to leave a lot of room for lefties - the root of handedness quite possibly is a random genetic mutation that pushed the language centers to the left hemisphere as the ancient human brain became more specialized. Without this particular genetic mutation, our brains still might have evolved to their present levels of sophistication, but our language hemispheres would be chosen at random, meaning handedness would be more evenly split.

In fact, a second major gene mutation might have had precisely that effect, at least in a subset of the population. University College London neuropsychologist Chris McManus suggests that sometime between 20,000 and 100,000 years ago, a second mutation entered the human gene pool that canceled out the brain's natural bias towards right-handedness, allowing for the emergence of more left-handers. People who carry this second mutation are also more likely to have unusual patterns of brain organization, which neatly explains why lefties are more to have both high intelligence and mental disorders.

So is it really all about language?

Well...that's just one theory. It's a pretty good one, as theories go, but it doesn't explain everything, and - as we've just seen - it very easily gets wrapped up in grand triumphal stories of humanity's brilliant evolution. Certainly, we should be careful in saying the development of language centers in the left hemisphere caused the rise of handedness. The two appear linked, but it may not be quite as direct as we might have imagined.

One issue is that we're not the only other animals to use a particular hemisphere of the brain to create noises. Birds and frogs, for instance, process the noises they make in one particular side of the brain, and there's no evidence of handedness in the way they use their limbs. University of Auckland researcher Michael Corballis suggests an alternative explanation for our handedness in the Discover article:

"It's quite possible that what set humans apart was that speech began from gestures, which would explain an indirect association with handedness. But it's one of those mysteries that refuses to resolve itself. Think of it this way: Primates do have very symmetrical brains, but then again, so did Einstein."

The division of labor theory and the two genetic mutations don't need to be thrown out - instead, we can roll them into a larger picture of the evolution of handedness. It's possible that the specialization of our brains were already pushing our species toward handedness, but this process was accelerated by the activities of ancient humans, in particular their use of tools. In a 2009 blog entry for Science, Michael Balter details one possible explanation for the rise of handedness:

The "technology-dense lifestyles" of early hominins might have required our ancestors to more or less make up their minds about what hands they were going to use to perform complex tasks. Moreover, such hand bias could have aided the learning process as hominins taught each other toolmaking and other skills; a number of studies have shown that people learn manually difficult tasks, such as knot-tying, more easily when they use the same left- and right-hand movements as their teachers.

We can also add into the mix the development of longstanding, pervasive social prejudices against left-handedness, which I'll discuss in more detail in a little bit. These prejudices likely influenced countless children who otherwise would have developed into lefties to essentially force themselves to be right-handed, effectively inflating the proportion of the right-handed population.

When did handedness first evolve?

We can feel reasonably confident that Neanderthals and Homo heidelbergensis were right-handed. Neanderthal skeletons tend to have stronger right arms and shoulders than their left counterparts, perhaps because they used them to throw spears while hunting animals. There's less direct evidence for Heidelbergensis, but we can tell from their preserved teeth indicate that they ate food with their right hands. The 1.6 million year old Homo ergaster skeleton Nariokotome Boy showed signs of right-handedness, but we can't infer the hand preference of an entire species from just one skeleton.

Determining the handedness of other primates is also tricky for a bunch of reasons. In general, wild primates aren't particularly likely to engage in the sorts of activities that require fine motor skills - and thus would require handedness - and it's hard to know whether we can really trust results we get from giving human-like tasks to captive primates. But as primatologist Bill Hopkins explains in the Discover article, decades of accumulated research have given us some rather unexpected answers:

A close look at primate research since the 1920s shows that all primates have hand preferences, and those preferences follow a clear pattern: Lemurs and other prosimians tend to be left-handed; macaques and other old-world monkeys are evenly split between lefties and righties; among gorillas and chimpanzees, 35 percent are lefties, while in humans that percentage hovers around 10. In other words, the more primitive the primate, the more likely it is to be a lefty. Left-handedness, far from being a recent invention, seems to predate right-handedness.

We know that the ancestor of all primates evolved about 65 to 85 million years ago as a member of the extinct order Plesiadapiformes. One of the last of the Plesiadapiformes was Carpolestes simpsoni, which had grasping digits like those of all its primate descendants. It's possible that the development of handedness goes right back to this very ancient transition from claws to digits.

Why primates apparently slowly moved from left-dominant to right-dominant as they evolved remains an open question. We could go back to the division of labor theory here. It's possible that because Carpolestes simpsoni and the earliest primates had small brains, they had to cluster control of their emerging motor skills in one hemisphere, which just happened to be the right.

This led to a lot of left-handed monkeys, but as larger, bigger-brained primates began to evolve, this division of labor became less important, which opened the door for a wider mix of righties and lefties. Of course, that doesn't explain why handedness started to swing towards righties as we get to chimps and gorillas is still - it's certainly possible that changing brain structure and random mutations played a major role, but we just don't know for sure.

What does it actually mean to be right-handed or left-handed?

After everything we've already discussed, that may seem likely a stupidly easy question, but it's surprisingly controversial. The everyday answer to that question is probably this: if you write with your right hand, then you're right-handed. It's a straightforward enough popular definition, but translating that into scientific terminology is trickier than you might think. Even simply saying that handedness is determined by which hand you prefer to use doesn't actually help us that much.

Let's consider some of the problems here. Should a person's dominant hand be determined by the hand they prefer to use, or the hand that performs better in tests? In other words, is handedness primarily psychological or physiological? Even if you can sort that out, there's still the question of how to categorize all this. Should left-handed and right-handed be considered precisely equal, or does the fact that such a vast majority of people are right-handed suggest that the people are simply either right or non-right? That's a bit of a charged way to look at things, but it does have some popularity in scientific literature.

And how about people who use different hands for different tasks? I write and throw with my right hand but bat and play(ed) hockey with my left hand - should I be considered primarily right-handed, a mix of right- and left-handed, or ambidextrous, meaning I feel equally comfortable using both hands? (Yeah...I'm probably not ambidextrous.) And should we look at handedness as something that can be lumped into only a very few categories - say true right-handed, more right-handed, ambidextrous/mix, more left-handed, and true left-handed - or something that exists on a broad spectrum?

Indeed, the very idea that one hand is "dominant" might be a complete misunderstanding of how our hands divide up tasks. In the Science post, Michael Balter details an argument by University of Liverpool archaeologist Natalie Uomini:

Uomini points out that handedness does not mean that one hand is "dominant" over the other. Rather, she writes, "both hands have different but equally important roles." In right-handed people, for example, the right hand might be used for tasks requiring greater manual dexterity whereas the left hand might perform the more mundane but nevertheless crucial role of supporting an object. (Imagine eating dinner with just a knife but no fork, for example.)

There isn't a ton of consensus here - ask a dozen scientists and you'll probably get at least ten different ways to define and organize handedness. Part of the problem here is that handedness is generally a pretty touchy issue, one with a long history of bias and prejudice. Speaking of which...

What exactly do people have against lefties?

For reasons that can probably best be described as "stupid", people have historically held left-handers in contempt. You can find evidence of an anti-left bias throughout the world's languages. The word "left" itself comes from the Anglo-Saxon word "lyft", which means "weak." We get the word "sinister" from the Latin word for "left", and that double meaning persists in the modern Romance languages.

It really is an insanely long list - English, French, Chinese, Korean, Finnish, Irish, Hungarian, Dutch, Spanish, Italian, Portuguese, German, and most of the Slavic languages all either link the word "right" with goodness, the word "left" with wrongness and impropriety, or both. That's not even getting into all the expressions and customs that have sprung up against left-handed people. In Ghana, even gesturing with the left hand can be considered taboo, and a common form of 19th century bigotry was to say minority groups such as homosexuals and Roman Catholics were left-handed.

As to why these prejudices exist - well, it does appear that majority right-handedness has been around at least since modern humans first emerged 200,000 years ago. This may simply be a case of a natural majority picking on a minority, perhaps out of an embarrassingly human fear of what's different. There's also at least one possible vaguely practical reason for this animosity. As any lefty will be happy to tell you, tons of everyday objects that right-handed people take for granted are a pain in the ass to use if you're a lefty. There's spiral notebooks, can-openers, stick shifts...and that's just what I remember from the Simpsons episode on the subject.

It's possible that ancient tools were similarly designed with right-handed users in mind, and the natural difficulties a lefty would have with such implements could draw social scorn and, over time, build up negative associations towards lefties. That all sounds fairly fanciful, honestly - although a few languages do have words that mean both "left" and "clumsy", suggesting a linked meaning somewhere along the line. Ultimately, we're probably just looking at good old-fashioned fear of the unusual.

There's really no definitive evidence either way that righties are better than lefties or vice versa - they just happen to hold their pencils differently. And while there have been a bunch of attempts to tease out specific differences between the two groups - including a recent study that basically suggested left-handedness is a form of cognitive impairment - there's way too much conflicting data out there to say much for certain.

As Chris McManus observed in the Discover article, ""The real question is why everyone wants left-handers to be defective", and there's a great deal of truth to that observation both throughout history and right up to now. Anyway, if this whole exercise has taught us anything, it's that we're probably just a couple random genetic mutations away from left-handers snootily trying to figure out what's up with that 30% minority of righties.

Further Reading

Is being left-handed a form of cognitive impairment? by Alasdair Wilkins
The Biology of Handedness by Jocelyn Selim
The Origins of Handedness by Michael Balter
What does Handedness have to do with Brain Lateralization (and who cares?) by M.K. Holder
Wild chimpanzees show population-level handedness for tool use by Elizabeth V. Londsor and William D. Hopkins

Image Credits

Top image by M.C. Escher.
Cerebral lobes via Wikimedia.
Green frog by thatredhead4 on Flickr.
Carpolestes simpsoni by Sisyphos23 on Wikimedia.
Leftorium via Loonpond.

Even in decidedly "wealthy" countries, human health is not always guaranteed. In fact, studies show that the best indicator of a country's health is not its overall wealth, but how that wealth is distributed. Time Magazine's Maia Szalavitz reports:

Imagine there was one changeable factor that affected virtually every measure of a country's health- including life expectancy, crime rates, addiction, obesity, infant mortality, stroke, academic achievement, happiness and even overall prosperity. Indeed, this factor actually exists.

It's called economic inequality. A growing body of research suggests that such inequality - more so than income or absolute wealth alone — has a profound influence on a population's health, in every socioeconomic group from rich to middle class to poor.

Economic inequality is measured by looking at the distribution of wealth and income in a society, not the general wealth of a country. At a basic level, a country's overall economic success does predict its people's well-being, but the healthiest and happiest countries in the world are not the richest. Rather, they are countries where wealth is shared widely and more equally.

One of the most obvious ways that economic equality may improve a country's overall health is by improving access to health care for all of its citizens, but Szalavitz writes that poor overall health manages to persist, "even in countries with national health services." So from where, exactly, does the negative correlation between economic inequality and public health stem?

"The roots of the problem," write Szalavitz,"appear to reach deeper than [access to public health care]. Indeed, they may go back to the dominance hierarchies of our primate ancestors."

Read the rest of Szalavitz's excellent piece over at TIME.
Top image via

Order the book

A review of Richard Dawkins’ The God Delusion (Bantam Books, 2006, ISBN 0618680004). This review was originally published in Science, January 26, 2007.

There is no position on which people are so immovable as their religious beliefs. There is no more powerful ally one can claim in a debate than Jesus Christ, or God, or Allah, or whatever one calls this supreme being. The religious factions that are growing throughout our land are not using their religious clout with wisdom. They are trying to force government leaders into following their position 100 percent. If you disagree with these religious groups on a particular moral issue, they complain, they threaten you with a loss of money or votes or both. I’m frankly sick and tired of the political preachers across this country telling me … that if I want to be a moral person, I must believe in A, B, C, and D. Just who do they think they are?

Such stirring words, spoken with such moral conviction, must surely come from an outraged liberal exasperated with the conservative climate of America today, and one can be forgiven for thinking that in a review of The God Delusion these are the words of Richard Dawkins himself, who is well known for not suffering religious fools gladly. But no. They were entered into the Congressional Record on 16 September 1981, by none other than Senator Barry Goldwater, the fountainhead of the modern conservative movement, the man whose failed 1964 run for the presidency was said to have been fulfilled in 1980 by Ronald Reagan, and the candidate whose campaign slogan was “In Your Heart You Know He’s Right.”

If Goldwater had been president for the past six years, I doubt that Dawkins would have penned such a powerful polemic against the infusion of religion into nearly every nook and cranny of public life. But here we are, and like Goldwater, Dawkins is sick and tired of being told that atheists are immoral, second-class, back-of-the-bus citizens. The God Delusion is his way of, like the Howard Beale character in the 1976 film Network, sticking his head out the window and shouting, “I’m as mad as hell, and I’m not going to take this anymore.”

But The God Delusion is so much more than a polemic. It is an exercise to “raise consciousness to the fact that to be an atheist is a realistic aspiration, and a brave and splendid one. You can be an atheist who is happy, balanced, moral, and intellectually fulfilled.” Dawkins wants atheists to quit apologizing for their religious skepticism. “On the contrary, it is something to be proud of, standing tall to face the far horizon, for atheism nearly always indicates a healthy independence of mind and, indeed, a healthy mind.”

Dawkins also wants to raise consciousness about the power of Darwin’s dangerous idea of natural selection. He believes that most people — even many scientists — do not fully understand just how powerful an idea it is. He attributes that failure to the need to be steeped and immersed in natural selection before you can truly recognize its power. In this context, natural selection “shatters the illusion of design within the domain of biology, and teaches us to be suspicious of any kind of design hypothesis in physics and cosmology as well.”

Out of obligation, of course, Dawkins reviews and offers rebuttals to all the standard arguments for God’s existence. He concentrates on dissecting the anthropic principle and dismantling intelligent design creationism. (As part of the latter efforts, he redirects the creationists’ argument from complexity to show that God must have been designed by a superintelligent designer.) He then builds a case for “why there almost certainly is no God.” The remainder of the book outlines possible evolutionary origins of morality and religious belief, a justification for being hard on religion, childhood religious indoctrination as child abuse, and an elegant commentary on the progressively changing moral zeitgeist. Dawkins closes with a tribute to the power and beauty of science, which no living writer does better.

When I received the bound galleys for The God Delusion, I cringed at the title, wishing it were more neutral (why not, say, The God Question?). As I read the book, I found myself wincing at Dawkins’s references to religious people as “faith-heads,” as being less intelligent, poor at reasoning, or even deluded, and to religious moderates as enablers of terrorism. I shudder because I have religious friends and colleagues who do not fit these descriptors, and I empathize at the pain such pejorative appellations cause them. In addition, I am not convinced by Dawkins’s argument that
without religion there would be “no suicide bombers, no 9/11, no 7/7, no Crusades, no witch-hunts, no Gunpowder Plot, no Indian partition, no Israeli/Palestinian wars, no Serb/Croat/Muslim massacres, no persecution of Jews as ‘Christ-killers,’ no Northern Ireland ‘troubles’…” In my opinion, many of these events — and others often attributed solely to religion by atheists — were less religiously motivated than politically driven, or at the very least involved religion in the service of political hegemony.

I also never imagined a book with this title would ever land on bestseller lists in the United States. But I was wrong. The data have spoken. The God Delusion is a runaway bestseller, a market testimony to the hunger many people — far more, I now think, than polls reveal — have for someone in a position of prestige and power to speak for them in such an eloquent voice. The God Delusion deserves multiple readings, not just as an important work of science, but as a great work of literature.

The hagfish is an evolutionary throwback that definitely lives up to its name. When the eel-like creature finds a carcass on the seafloor, it burrows inside the dead meat and starts eating...not just with its mouth, but with its skin.

The trick of absorbing nutrients not only through the mouth but through the skin and gills is practiced by a few other simple sea creatures, such as the mollusk. But all of those creatures were invertebrates - the hagfish is the first vertebrate ever discovered that eats in this way. That isn't exactly surprising, as the hagfish is essentially a living fossil, the oldest surviving link back to the first ever vertebrates.

Hagfish are extraordinarily simple, resembling little more than tubes. They are almost completely blind and, as University of British Columbia researcher Carol Bucking describes:

"Their most striking feature, besides the ability to exude thick, gel-like slime in copious amounts when disturbed, is the whisker-like appendages around their mouths that they use to explore the environment."

So, these aren't complicated creatures. But, as with most adaptations, their ability to process food through their skin and gills is rather ingenious and even elegant, despite the fact it seems pretty disgusting from our perspective. Carcasses are not often found, and when the hagfish do come across a food source they have to make the absolute most of it, particularly because other scavengers could show up at any moment. The ability to absorb nutrients all over its body allows the hagfish to keep going well into its species's 360,000,000th year on this planet.

Via LiveScience.

The Atlantic tomcod that live in the heavily polluted Hudson River have come up with an extreme solution to deal with all the toxins surrounding them: mutate, and mutate fast. But though their super-speedy adaptation has allowed them to survive over thirty years in the dirty rivers, it may have come at a terrible price.

These tiny brown fish live just downriver of a bunch of General Electric plants, which had been steadily dumping waste in the river for decades until the practice was halted in the early 1980s. But the damage was done, and the particularly dangerous chemicals, polychlorinated biphenyls (PCBs) and dioxins, can still be found in heavy concentrations throughout the Hudson. When the dumping stopped thirty years ago, 94% of the adult tomcod had a PCB-induced tumor on their liver.

After making that initial discovery, New York University researcher Isaac Wirgin spent decades studying how the tomcod changed to meet this devastating new ecological paradigm. The results were shocking:

I started working on these fish with the hypothesis that they would be very sensitive to the toxic effects of PCBs. But the more work we did in controlled lab studies, we found that they were highly resistant to the toxic effects of PCBs and dioxin."

Yes, in the last thirty years, the tomcod have mutated, and every fish that has ever been taken out of the river in the last few years has been found to possess a gene that greatly reduces the dangers of PCBs and dioxins. It's allowed the fish to survive in waters that would be lethal to their counterparts elsewhere, but the fish have suffered in other ways. They likely grow slower than other tomcod, and they may have reduced resistance to other dangers.

But the real concern is that these fish aren't getting rid of the toxins - they're actually shunting the chemicals up the food chain:

"They serve as a prime prey for striped bass. You've got this fish that would normally be dead from PCBs or dioxin. It's alive and it's carrying around all this PCB and dioxin and it gets eaten."

The helpful mutation that has allowed the tomcod to survive involves a particular gene that, normally, would cause molecules in the fish to bind together with the toxic molecules, triggering a number of severe health problems. But the mutation discourages this action. All the fish tested possess this mutation, and 95% possess a second copy of the gene for extra protection. Only 5% of the fish in the nearby, relatively clean waters off Connecticut and Long Island possess the mutated gene.

Wirgin suspects other animals may possess the capacity for this sort of ultra-fast adaptation:

"I don't know what percent of species in a highly contaminated spot are going to be resistant. It's probably not that rare of an occurrence."

Science via Discovery News.

Almost everybody has a dominant hand that they use, but it's actually a mystery why that is. After all, we can see both of our hands just as well, and there's no built-in reason why one should work better than the other. But some grabby parrots might hold the deep evolutionary reason behind handedness.

Researchers had 322 parrots from 16 different species attempt to pick up an object beneath them with their feet. Because parrots have eyes on the side of their heads, they can't look directly down at the object to help them pick it up. Instead, they have to cock their head to one side or the other to see what they're trying to grab.

The parrots consistently showed a preference for grabbing the object with one foot or the other, and this was in turn reflected by how they cocked their head. For instance, let's say the parrot was right-handed - or, perhaps more accurately, right-footed. In that case, the parrot would almost always cock its head to the left to give its right eye a good view of what was going on below. The right eye would be better equipped to track the movement of the right foot, and so it would grab the object with that foot.

This connection between eyes and handedness isn't something we humans have to worry about, because our eyes are both on the front of our face. But eyes on the side of the head do raise these issues when dealing with things outside the normal field of vision, like the objects beneath the parrots. If our long distant evolutionary ancestors exclusively had eyes on the sides of their heads, that would explain a lot about why handedness evolved and why we humans still possess it.

Via Biology Letters and ScienceNow.

The most famous philosopher of the Victorian age, Herbert Spencer, coined the term "survival of the fittest", tried to apply the concepts of evolution to human society, and was described by Charles Darwin himself as "twenty times my superior." He was also a shameless hypochondriac, a sadistic prankster, and liked to dress in a one-piece suit that made him look like a bear.

On The Origins Of Herbert Spencer

Herbert Spencer was born on April 27, 1820 in Derby, England, the son of William George Spencer, a religious dissenter with a love of learning and an anti-authoritarian streak. The older Spencer instilled these values in his son Herbert, teaching him the basics of scientific empiricism while his friends in the Derby Philosophical Society - an organization founded by Charles Darwin's grandfather Erasmus, and of which George Spencer was secretary - gave the younger Spencer lessons in biology, particularly the proto-evolutionary ideas of Jean-Baptiste Lamarck and Erasmus Darwin.

Beyond some math and Latin lessons from his uncle, the Reverend Thomas Spencer, the rest of Herbert's education was completely self-taught. Herbert Spencer had a remarkable ability to extract all possible information from a chosen text, carefully picking out readings that would expand his understanding of a given topic. He also gained as much information as he could from those he spoke with, folding the knowledge of all those he met into his own rapidly growing intellect.

Spencer bounced around a few jobs, finding success as a young man writing and editing various radical journals advocating for free trade. His ideas were a mix of cutting edge economic theory and proto-Darwinian notions of evolution, which together he used to chart the future of humanity. In 1851, he published Social Statics, which danced around the concept of "survival of the fittest" that he would coin fifteen years later. Consider this passage, which melds social theory with notions of Lamarckian evolution:

"It is clear that any being whose constitution is to be moulded into fitness for new conditions of existence must be placed under those conditions. Or, putting the proposition specifically - it is clear that man can become adapted to the social state, only by being retained in the social state...Only by the process of adaptation itself can be produced that character which makes social equilibrium spontaneous."

Man Of The Salon

As Spencer gained so much of his knowledge from those he conversed with, it was hugely important for Spencer to pick the right friends. On this point, he was helped by Social Statics publisher John Chapman, who brought him into contact with an intellectual salon full of the United Kingdom's most radical thinkers. Interaction with these men and women cemented his political philosophy, a libertarian system that believed the natural progression of humanity would make all government wither away. To this end, Spencer at times advocated for universal suffrage for women and children, and he argued for the nationalization of land to diminish the power of the aristocracy.

The salon's ranks included the utilitarian philosopher John Stuart Mill, literary critics and religious skeptic George Henry Lewes, pioneering sociologist Harriet Martineau, and writer Mary Ann Evans, better known as pseudonymous Silas Marner author George Eliot. Spencer became particularly close to Lewes and Evans, and Evans even once proposed marriage to him, although Spencer turned out to be just one of several men who did not reciprocate her more romantic feelings.

Lewes and Evans helped bring Spencer's thinking to the next level, and the result was 1855's Principles of Psychology, in which Spencer argued the workings of the human mind were fundamentally knowable through application of natural laws. This pronouncement staked out a position in extreme opposition to that of religious orthodoxy, which maintained certain parts of the world - the human consciousness chief among them - were inherently beyond the understanding of science. This made Spencer's book unpopular with the establishment, and it failed to achieve much critical or public support. Still, Spencer was just getting warmed up.

The Other Father Of Evolution

As early as 1852 - seven years before Charles Darwin went public with his evolutionary theories in On the Origin of Species - Herbert Spencer sketched out the basics of evolution and natural selection. His basic idea was that human development was naturally progressive and everywhere increasing. This optimistic view led him to what he termed "evolution", arguably making him the real popularizer of this term, not Darwin. The key distinction is that Spencer could not advance an actual theoretical framework for this evolutionary process, which Darwin was able to do with his notions of natural selection.

Spencer's philosophy became hugely popular, offering the growing intellectual class a ready-made substitute to conventional religion. His system suggested everything from biological evolution to the laws of thermodynamics could be used to predict the future of humanity and, more specifically, the future perfection of humanity. The cosmos existed to promote human happiness, as far as Spencer was concerned, and the laws of nature were universal in their reach.

But let's focus on Spencer's take on evolution, because it could take years to unravel his entire argument. It's important to keep in mind that Spencer was not simply taking Darwin's ideas and applying them to society as a whole. It's an understandable mistake - indeed, what other assumption is possible when Spencer is generally credited as the inventor of something called "Social Darwinism"?

In actual fact, Spencer was more comfortable with Lamarck's earlier notions of acquired characteristics, which hold that how particular organs or traits are used during a person's lifetime can affect their physical makeup and then be passed down to their children. Darwin's idea of a directionless evolution, in which there was no endpoint but simply adaptation to changing environmental niches as governed by natural selection, was not an easy fit for Spencer's earlier ideas, and it was only with some reluctance that he incorporated these ideas into his work.

Survival Of The Fittest

Spencer's most famous idea is encapsulated by "survival of the fittest", although it's often mistakenly attributed to Charles Darwin. Spencer came up with this iconic turn of phrase in his 1864 book Principles of Biology, in which he writes:

"This survival of the fittest, which I have here sought to express in mechanical terms, is that which Mr. Darwin has called 'natural selection', or the preservation of favoured races in the struggle for life."

Darwin would then use the phrase himself in the fifth edition of On the Origin of Species, although his use was only metaphorical, and not intended as a scientific description. Indeed, the term doesn't really capture the evolutionary process, as it's not just the fittest that survive to reproduce - it's all organisms that are fit enough to not die young, which has led later biologists to suggest "survival of the fit enough" is the more accurate term.

Besides, Spencer's use of the phrase might have been redundant, a mere tautology. He seemed to use "fittest" as "best-equipped to survive", which makes the phrase "survival of the best-equipped to survive" a bit useless. Still, though his ideas proved a clumsy fit for the actual science of evolution, they captured - and still capture - the public imagination, and they proved to be much better fits for Spencer's primary concern, which was an evolution-based theory of society.

A Word About Social Darwinism

In general, Spencer's positive reputation is as the coiner of "survival of fittest" and as the popularizer of Darwin. His negative reputation comes from his attempts to wed these ideas to society at large. Social Darwinism - the term generally applied to Spencer's sociological efforts - is often thought of as apologism for the wealthy, as it says those who are successful in society are those best-adapted to it, meaning the poor are less fit to survive in society.

It's an understandable misconception, and other philosophers have advanced ideas more along those lines, but that wasn't really what Spencer was driving at. The main focus of his social evolution was focused on the state itself, which he basically believed evolved first to give society structure, and then withered away as the members of that society were sufficiently evolved to do without it. (This is, like most paragraph-long summaries of a lifetime's work, something of an oversimplification. But it will do for our purposes.)

As we previously mentioned, his writings proved staggeringly popular, and he became the most famous philosopher of the Victorian Age. He became an international inspiration for revolutionary groups looking for an innovative system that could replace their failed states, and his ideas were influential in various movements as far away as Poland, China, and Japan. No less than Charles Darwin called him "twenty times my superior", and wrote these glowing words:

"Every one with eyes to see and ears to hear (the number, I fear, are not many) ought to bow their knee to you, and I for one do."

Spencer was often compared favorably to Aristotle, and there's a decent argument that he was, in his own time, the most famous philosopher ever. But as interesting as Spencer's ideas were, the man behind those ideas was often far more fascinating. Let's now consider just who Spencer really was...because he was a strange man indeed.

The Hypochondriac And The Hammock

Herbert Spencer was never particularly healthy, and his constant intellectual exertion took its toll on his frail physique. Of course, no one was more keenly aware of this than Spencer himself, who spent the final decades of his life an incorrigible hypochondriac, constantly complaining of various illnesses that no doctor could ever diagnose. Chief among these was "the mischief", an odd sensation he sometimes felt inside his head.

Amazingly, Spencer was by far the strongest member of his family - tragically, he was the only one of William George Spencer's nine children that even reached adulthood. He was known to be a chronic insomniac, which kept him in a state of perpetual exhaustion that limited his ability to work to just a few hours a day, and he suffered a series of nervous breakdowns. These bouts didn't do wonders for his social skills, as he often took to wearing earplugs whenever he felt over-excited...particularly if he was on the verge of losing an argument.

Traveling was a particular ordeal for Spencer, and he was constantly convinced that any coach ride would spell his doom. Indeed, he would frequently demand the coachman pull over so that Spencer could check his pulse, just to be absolutely certain he was still alive. The fact that the coachman had responded to him at all should have been proof enough, really, but Spencer was nothing if not thorough.

Train rides weren't much better. Spencer kept two men on constant retainer to help him whenever he got on a train. One of the assistants was in charge of his traveling hammock, which would be set up in his compartment and Spencer would clamber in, where he remained for the length of the stay. The rest of the work consisted of moving all his luggage, which included several rugs and air cushions meant to increase the comfort of the trip.

But the strangest part had to be how Spencer was dressed. He had designed a rather ridiculous-looking one-piece, overall-like costume, and this became his preferred thing to wear. It was designed to reduce the great effort it took to wear all that excessive Victorian attire, as Spencer now had no need to wear boots, socks, pants, shirt, or a coat. There was a trade-off though - Spencer looked like a big brown bear whenever he wore his overalls. On second thought, maybe that wasn't really a trade-off.

Is It Water On The Brain?

Still, Spencer wasn't so obsessed with his health that he couldn't enjoy himself. He could have a wicked sense of humor, as a fellow academic named Trimbell discovered. Hydrocephalus, better known as water on the brain, was one of the most feared conditions of the Victorian world, and it wouldn't be until the 20th century that medical science came up with effective treatments for the disease.

Hydrocephalus occurs when an unusually high amount of cerebrospinal fluid accumulates in the cavities of the brain. Although it mostly affects a small percentage of newborns, it is possible for adults to acquire the condition well. The condition is known to be extremely painful for any adults who contract it, and the damage it does to the brain can seriously affect thought and behavior.

So yes, that's the condition Spencer decided to convince his colleague Trimbell that he had. After outlining these symptoms and pointing out a swelling head was the first sign of hydrocephalus, Spencer started to sneakily add strips of paper inside his friend's hat. Every day Spencer added another tiny strip of paper, each time making the space inside the hat a little smaller and a little tighter for Trimbell's head.

Spencer was playing a long game here - it took weeks for Trimbell to realize that his head was "growing", but once he realized he was most distressed at how fast his water on the brain was progressing. If there was any justice in the world, Spencer's longstanding hypochondria should have been the result of poor souls like Trimbell exacting their revenge, fooling him with a set of equally fraudulent maladies that would be impossible for doctors to detect. Maybe they can throw that in when Hollywood makes the Herbert Spencer biopic.

Spencer's End

As Spencer's health deteriorated, so too did his optimism in humanity. Spencer, once a champion of political ideals that fell somewhere between liberalism, libertarianism, and outright anarchy now drifted rightward towards reactionary conservatism. Spencer had always championed the progressive character of humanity, the notion that human minds and societies were always improving so that, eventually, no government would be needed. But, as his friends died off and he became increasingly isolated and lonely - Spencer was a lifelong bachelor - he became disillusioned with this view.

In a sense, the philosophical underpinnings of Spencer's politics hadn't really changed. He had been distrustful and skeptical of government his entire life, but what had once been a more abstract critique became increasingly focused on the policies of Prime Minister William Gladstone, the Grand Old Man of the Liberal Party. Spencer's once revolutionary views slipped away one by one - he now opposed suffrage for women, and he now sought to protect the rights of traditional landowners against what he saw as the rising tide of socialism.

On one point, Spencer's old anti-conservatism remained, but it made him staggeringly unpopular. Spencer remained staunchly anti-military and anti-imperialism, and his final days were spent bitterly critiquing the Boer War. His once near universal influence was already on the wane, and a public that had once seen Spencer as the philosopher now dismissed him as a bitter old crank.

Survival Of The Fittest Reborn

Spencer died in 1903. He was cremated, with his ashes interred in London's Highgate Cemetary. In an odd coincidence, his gravestone faces that of Karl Marx. It seems appropriate that, even in death, Spencer would be provided with someone with whom he could have a fierce philosophical argument.

The backlash against Spencer, which had already begun before his death, reached its apex in the early 20th century. The most popular philosopher of the Victorian Age was now dismissed as a clueless buffoon whose works were little more than an unintentional parody of real philosophy.

In his 1944 book Social Darwinism in American Thought, historian Richard Hofstadter did what is known in academic circles as ripping him a new one, blasting Spencer as "the metaphysician of the homemade intellectual, and the prophet of the cracker-barrel agnostic." Even more damagingly, it was Hofstadter who popularized the notion of Social Darwinism. It's an idea that, yes, is an important aspect of Spencer's work, but it's just one part of a rich, complex philosophical doctrine that often gets swept aside in modern discussion.

The last few decades have been far kinder to Spencer, and he's enjoyed a positive philosophical reappraisal. Although his personal fame has long since been eclipsed by Charles Darwin, his ideas are arguably still better known than those of the father of biological evolution. After all, ask a random person on the street what's the first thing they think when you mention "evolution." (Note - please don't actually do this. They might be busy.) Some will say "natural selection", yes, but just as many will say "survival of the fittest." Even if most people don't know the real context of that phrase, it lives on in our cultural lexicon.

And Now, At Last, The Paper Clip

There's one other notable story about Herbert Spencer that we haven't yet touched - that he invented the paper clip. This is more or less an urban legend. The first paper clip is generally credited to the American inventor Samuel Fay, who panted the bent wire paper clip in 1867. His was one of about fifty paper clip designs patented before 1900, although none of them are actually all that similar to what we use today.

But where does Spencer enter into all this? He did mention in his autobiography that he had invented what he called a "binding pin", which at the time was distributed by the firm Ackermann & Company. An appendix to his autobiography includes a drawing of the pin, and it doesn't really look much like what we now consider a paper clip. It does look like cotter pins, sometimes known as an R-clip. You can see one above.

Of course, it is a perfectly workable design, and Spencer's apparent invention (there's technically no proof for his claims outside his autobiography) is one of the earliest known examples of a cotter pin. And besides, it was meant to hold together sheets of paper, so if we're being technical about this, it could certainly be considered a paper clip, even if it doesn't really fit the more precise definition of the term.

So now, if someone ever tries to impress you by mentioning that the "survival of the fittest" guy invented the paper clip, you can kindly correct them and tell them the real story of Herbert Spencer. Personally, I'd advise starting with his bear-looking one-piece.

You probably know that you can't tickle yourself. And although you might be able to tickle a total stranger, your brain also strongly discourages you from doing something so socially awkward. These facts offer insight into tickling's evolutionary purpose.

According to Robert R. Provine, a neuroscientist at the University of Maryland, Baltimore County, and the author of the book Laughter: A Scientific Investigation, tickling is partly a mechanism for social bonding between close companions and helps forge relationships between family members and friends.

Laughter in response to tickling kicks in during the first few months of life. "It's one of the first forms of communication between babies and their caregivers," Provine says. Parents learn to tickle a baby only as long as she laughs in response. When the baby starts fussing instead, they stop. The face-to-face activity also opens the door for other interactions.

Children enthusiastically tickle one another, which some scientists say not only inspires peer bonding but might help hone reflexes and self- defense skills. In 1984 psychiatrist Donald Black of the University of Iowa noted that many ticklish parts of the body, such as the neck and the ribs, are also the most vulnerable in combat. He inferred that children learn to protect those parts during tickle fights, a relatively safe activity.

Tickling while horsing around may have also given rise to laughter itself. "The ‘ha ha' of human laughter almost certainly evolved from the ‘pant pant' of rough-and-tumble human play," says Provine, who bases that conclusion on observations of panting among tickle-battling apes such as chimpanzees and orangutans.

In adulthood, tickling trails off around the age of 40. At that point, the fun stops; for reasons unknown, tickling seems to be mainly for the young.

Photo: Thomas Marent/Getty Images. This post originally appeared on Popular Science.

Hiccups don't serve a useful function anymore, but they were useful to our very ancient ancestors. Find out how early fish 'hiccuped' in order to breath underwater.

Hiccups are a great way to ruin a good meal, a sad movie, or a first date. They're annoying, sometimes painful, and completely useless. That is, they're completely useless to humans. To early fish and amphibians, the motion of a hiccup was vital to continued survival. Humans' ever-so-great-grandcestors were just beginning to use lungs to crawl out of the water. When roaming the land, they needed to suck air down into their lungs.

When they plunged back into their watery homes, they needed to keep their lungs free of liquid. To accomplish that, they had the ability to close the glottis, the passageway into their lungs. They would muscle closed the glottis, sealing off the lungs when they were underwater. At the same time, they would suck water back, forcing it over their gills to allow them to oxygenate themselves while underwater. The motion would push the closed glottis back and down.

So the motion was as follows: a sudden indrawn breath, meant to pull things into the mouth, and a sudden closure of the airway, stopping anything from actually reaching the lungs. Sound familiar? The motion of a hiccup is what allowed early human ancestors to go from air to water to air again. Today, when we only breathe air and leave water to those in wetsuits, it's just a vestigial twitch.

Via: Smithsonian.com.

Eighty DNA variants associated with type-1 diabetes have undergone positive selection, increasing in prevalence over recent generations. Here's the crazy part - 58 of those variantsincrease the risk of the deadly disease. Why is evolution seemingly out to get us?

The answer, of course, is that evolution can't be out to get us - by definition, positive selection of genes and traits works to maximize our species's chance of survival. So something about those particular DNA combinations that increase the risk of type-1 diabetes must also be conferring some positive benefit that outweighs the dangers of diabetes.

Of course, it would have to be a pretty big benefit. Type-1 diabetes, also known as juvenile diabetes, primarily affects children by causing a potentially lethal shortage of insulin in their bodies. The fact that it affects people who haven't yet reached reproductive age is crucial - natural selection should pretty much always select against diseases that can kill people before they get a chance to pass on their genes. (On the other hand, there wouldn't be nearly as much evolutionary pressure on the more common type-2 diabetes, which mostly affects post-reproductive adults.)

Lead researcher Atul Butte, a biologist at Stanford medical school, explains the conundrum:

"At first we were completely shocked because, without insulin treatment, type-1 diabetes will kill you as a child. Everything we've been taught about evolution would indicate that we should be evolving away from developing it. But instead, we've been evolving toward it. Why would we have a genetic variant that predisposes us to a deadly condition?"

The best answer is that the genetic variants that increase the diabetes risk are also decreasing the risk of certain viral or bacterial infection. That would have made particular sense in a past where infectious diseases ran rampant, and the risks of dying young from these mostly untreatable illnesses far outstripped the dangers of diabetes. It's not yet clear whether the same mutated genes that increase the diabetes risk also provide this protection, or if it's neighboring genes whose allocation from generation to generation is intertwined with the diabetes gene.

Maybe the best example of this genetic phenomenon is seen with the disease sickle cell anemia. A particular recessive gene causes the painful, potentially deadly disease if both parents pass it along to their offspring. It's the sort of trait that natural selection would have weeded out if not for the fact that people with only a single copy of the gene have increased protection against malaria. As such, the sickle cell gene is a net positive, because more people are protected from malaria than become sickle cell patients. (Although that evolutionary balance might shift if we ever managed to wipe out malaria.)

The diabetes question is more complex than the sickle-cell anemia case because it's not limited to the mutation of a single gene. Complex diseases like diabetes are tied to a number of DNA variants, or locations where the nucleotide combinations vary between different people. These variants are known as single nucleotide polymorphisms, or SNPs for short. You can calculate a person's susceptibility to a particular disease by figuring out the net effect of his or her variants, which will likely be a mix of beneficial, malicious, and neutral.

Genome studies have revealed several hundred variants that can play a role in diabetes, so it's supremely complicated to figure out the precise interplay of all these different strands of DNA. Still, the raw numbers are striking - of the 80 DNA variants that have increased in prevalence, only 22 increase protection while 58 cause greater risk of developing the disorder.

There are some possible candidates for the diseases these variants are protecting against. For instance, the gene IFIH1 has been found to increase diabetes risk while also protecting against enterovirus infection, which can cause severe, possibly lethal, abdominal pains. Another disease the researchers found had a majority of increasing risk factors, rheumatoid arthritis, has had its less protective gene variants linked to a sharp decrease in tuberculosis risk.

Still, the picture is far from complete, and Butte and his team are going to keep testing more and more SNPs until they can figure out why natural selection keeps favoring a greater risk of diabetes over the alternative. Until then, Butte says it's a mystery with only the sketchiest answers available:

"It's possible that, in areas of the world where associated triggers for some of these complex conditions are lacking, carriers would experience only the protective effect against some types of infectious disease. Even though we've been finding more and more genetic contributions to disease risk, that's not really an appealing answer. There have got to be some other reasons why we have these conditions."

[PLoS ONE]

Segmentation, the replication of anatomical structures throughout the body, is found in many animal species. It's also a huge reason why all those species succeeded, and it comes from a single common ancestor 600 million years ago.

Specifically, segmentation refers to instances where identical anatomical units are repeated on the axis running from the top to a bottom of an animal. (So the fact that we have eyes, ears, arms, and legs that are all identical doesn't count as segmentation.) Obviously segmented species include centipedes and millipedes, in which a single structure is repeated dozens, even hundreds, of times over, but they're hardly the only examples. Anything from earthworms to humans can possess segmented features.

Three of the most basic groups of animals - arthropods (insects, arachnids, and crustaceans), vertebrates (most animals that we're familiar with), and annelid worms (sea and earthworms, basically) - all heavily make use of segmentation throughout their individual species, and yet they're very distantly related groups. Recent evidence indicates that the genes controlling segmentation are essentially the same in anthropod and worm species, indicating that there was indeed a single common ancestor, probably a worm-like creature, some 600 million years ago that proved phenomenally successful because of its ability to segment.

So why does segmentation provide such a huge evolutionary advantage, and why has it helped bring about such fantastic animal diversity? The answer might be quite simple: segmentation creates ready-made spare parts, producing duplicated anatomical units that can be repurposed as needed. If a species is under heavy pressure to fit into a changing environmental niche, it may need to develop new structures that can deal with the altered conditions. In that instance, it would be much easier to modify an existing organ than build a whole new one. Segmentation would give species a better shot at quickly adapting to new environments, which would create more pronounced changes in the species and, thus, greater diversity.

In that case, segmentation is the ultimate example of what Stephen Jay Gould dubbed an exaptation, in which a trait becomes extremely useful for reasons unrelated to its initial development. If nothing else, there's a certain evolutionary irony in that the exact duplication of body parts is responsible for why animal species all look so wildly different.

via Science

WE HUMANS have let loose something extraordinary on our planet – a third replicator – the consequences of which are unpredictable and possibly dangerous.

What do I mean by “third replicator”? The first replicator was the gene – the basis of biological evolution. The second was memes – the basis of cultural evolution. I believe that what we are now seeing, in a vast technological explosion, is the birth of a third evolutionary process. We are Earth’s Pandoran species, yet we are blissfully oblivious to what we have let out of the box.

• Evolution’s third replicator: Genes, memes, and now what?