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Biotech Science

Chimpanzees Shed New Light on Hand Preference 519

An anonymous reader writes "'Language skills are associated with the left side of the brain, and many scientists have said early humans developed a preference for their right hands when they acquired speech,' but Emory University's Yerkes National Primate Research Center has a new study that links hand preference to the motor skills area of the brain rather than the language part of the brain. 'That means lefties have probably been around much longer than believed -- at least 5 million years, when scientists say humans and apes branched on the primate family tree. And evolution has purposely kept them.'"
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Chimpanzees Shed New Light on Hand Preference

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  • by andorsch ( 833253 ) on Tuesday December 07, 2004 @06:47AM (#11016271)
    why? evolution is not a process of "optimisation" it is a selection process. Those who are "good enough" survive.

    Obviously there is no disadvantage for being left handed, why should there be a selection against it?

    • by Bwian_of_Nazareth ( 827437 ) on Tuesday December 07, 2004 @07:31AM (#11016421) Homepage
      There is a advantage of being left-handed - it is the element of surprise when you meet your foe. This obviously works only when the percentage of left-handed individuals is low enough - around 10 - 20 %, IIRC.

      I am left-handed and I can say I do take advantage of it. I play volleyball and it always takes some adjusting until the opponent starts to block my left hand instead of my right. Playing squash, opponent often let me play mostly forhand because they don't realise my weak side is the other one.
      And quite obviously, this is even true for two left-handed opponents playing against each other. With majority of my opponents being right-handed, I myself am taken bu surprise when I meet left-handed opponent.

      Obvously, this advantage is lesser in repeated encounters and lesser when there are more left-handed people around.

      • There is a advantage of being left-handed - it is the element of surprise when you meet your foe

        Most FPS games now have the option to make your character left or right handed when it's using an ae or something, so it's no more a surprise :)
      • good as one hand can get, I'm sure there are evolutionary good reasons to also have a good second hand. That'll keep left and right fairly equal, and then the "gap" to flip it around and use left as your primary and right as your secondary isn't that big.

        I think many people misunderstand evolution as a process towards a "superbeing", one obviously better than the last in every respect. It is just as much about providing a flexibility so that a species may adapt to changing circumstances. Being able
      • And as absolutely conclusive proof of this, I just got back from a squash match where I flogged the daylights out of my opponent for the first 2 games simply because he failed to note that I was a lefty. Of course, it didn't help that I used my /right/ hand during the warm up (a bit of a deception game ;-)

      • This is especially true in fighting sports, where having an unorthodox stance really throws your opponent off. This seems to support the theory that it was developed as a self-defense advantage.
      • There is a Scottish clan, the Kerr's, who are known for being left-handed and built their castle with a left-handed spiral staircase, to deter right-handed enemy attacks.

        Ferniehirst Castle [], Wikipedia article []

        (And yes, I am partly left-handed ;)

        • Eh? That doesn't make any sense.

          Yes, all castles spiral the staircase the same way, so that it is easier (for right handed people) to fight down than it is up.

          But this trick only works if both defenders and attackers are the same-handed.

          If the defenders are left handed and attackers right-handed, then this fails, since the defenders are impeded as well as the attackers. Flipping the direction of the stair, while meaning that the defenders have it easier, also makes it easier for the right-handed attacker
      • But you can't beat ambidextrious ;) Someone set you shallow? Someone set you wide? Switch up!
      • by Have Blue ( 616 ) on Tuesday December 07, 2004 @10:10AM (#11017400) Homepage
        "You are wonderful."
        "Thank you; I've worked hard to become so. "
        "I admit it, you are better than I am."
        "Then why are you smiling? "
        "Because I know something you don't know."
        "And what is that? "
        "I... am not left-handed!"


        "You are amazing."
        "I ought to be, after 20 years."
        "Oh, there's something I ought to tell you."
        "Tell me."
        "I'm not left-handed either!"
    • Obviously there is no disadvantage for being left handed, why should there be a selection against it?

      Could you please forward that insight to Logitech ?
    • by nickco3 ( 220146 ) on Tuesday December 07, 2004 @08:34AM (#11016665)
      There are clear disadvantages to being left-handed, in the life expectancy stakes us lefties hold our own until we reach about 33, then it swing decisely against us, with only 1 in 200 80 year-olds being lefties.

      Evolution ruthlessly selects against even slightly disadvantageous genes, those that incur an apparently small 1% reduction in offspring quickly dwindle down to nothing when you repeat that over 20 or 30 generations. Genetically inflicted conditions usually have some kind of balancing factor that keeps them in the gene-pool, e.g. sickle-cell gene seems to protect against malaria, which gave it a role in West Africa, but it is already be edged out of the US gene-pool where it is no longer required.
    • I think that the time scales involved here suggest your reasoning may not be far reaching enough to allow for the possibilities of a darwinist strategy in the species.
    • Well there must be a disadvantage however slight.

      Human inventions are at worst exclusively right-handed in design, agnostic at best and more usually slightly biased to right handed use. Think corkscrews, mice, and even the way that (the West) writes on a piece of paper.

      Therefore a left handed person is immediately at a disadvantage. Most of the time this makes no odds (except some fumbling or wrist pain perhaps), but I suggest where is a risk of harm through incorrect operation, that it might lead to sl

    • by YouHaveSnail ( 202852 ) on Tuesday December 07, 2004 @09:56AM (#11017279)
      And evolution has purposely kept them.

      I have a big problem with the word "purposely." Evolution does not do anything "purposely," or with intention. Natural selection is a process that applies to all things that reproduce, whether it's an ape or a computer virus, just as gravity applies to all things that have mass.
  • why choose? (Score:2, Interesting)

    by adeydas ( 837049 )
    if lefties has a better channce of using the brain's motor neurons, then why did evolution choose to have 2/3 righties in the chimp population. doesn't it goes against darwin's theory?
    • Only if it is passed down genetically... that's the crux. "Survival of the fittest" means "those most likely and best at passing down genetic material"
    • Seriously- take a look at your average lefty. Now take a look at an average righty. Isn't your average righty better looking?

      Of course my fiancee says I'm "right" all the time, so maybe it's gone to my head.

      'scuse me while I go sleep on the sofa again...
  • by physicsphairy ( 720718 ) on Tuesday December 07, 2004 @06:49AM (#11016279) Homepage
    "a new study that links hand preference to the motor skills area of the brain"

    So, essentially what they've proven is that the motor skills part of the brain may effect the development of our motor skills?

    Man, I can't wait until I get my Ph.D.! This research scientist stuff is going to be a piece of cake!

    • This was my first reaction too. Why the hell would hand preference be connected to the language part of the brain?
      • ... if all of two areas are consumed in motor skills, and then language comes along and pushes one area out...

        Just a thought. Maybe certain areas maintain large hand movements while talking are actually using both regions again.

      • I read the article quickly, and my perhaps incorrect resummarization is this: If the left side of the body is generally controlled by the right side of the brain, and it is the right side of the brain controlling motor functions, why is it that only about 10% of humans are left-handed? This statistic implies an association, not causation, between speech and right-handedness as left-hemisphere brain activities. The research is trying to use chimps, who don't speak as we do, to look for any causative evidenc
    • by Arker ( 91948 ) on Tuesday December 07, 2004 @08:44AM (#11016705) Homepage

      Being that this is related to my work, and I've been following the debate for awhile on it, I can tell you it's more complicated than this lame article makes it sound.

      Unfortunately I wasn't able to find a copy of their actual paper (it may not be published yet,) and newspaper articles just aren't conscious enough to be very usable as sources here. I have read some of this guys earlier papers, along with others, and I at least have some background on what they're talking about though.

      It's been known for quite some time that handedness is associated with Broca's Area [] a part of the brain generally associated with language. However, the simplistic equation of Broca's area = language is not necessarily true - our understanding of the brain isn't that fine-grained, Broca's area may have several function, or may actually be several organs we're conflating. It's also definately associated with some motor functions, for instance facial gestures, and it's been argued that it's primary function may be one of motor control, not language. So what exactly handedness being associated with Broca's means is still clearly up for debate.

      This paper by Corballis, [] is probably the best summary of recent research on the question that I'm able to find a clear link to for you right now - not that it's nearly thorough enough to serve that purpose really, but it does cover a lot of ground, and most articles like this are not available without subscription. Anyway, it has been argued that handedness was caused by language, but it's also been argued, for instance, that human language arose originally from a mixture of manual gestures, facial gestures, and involuntary vocalisations which change soundshape with those facial gestures, thus becoming distinguishable representations of them. In this scenario, Broca's primary function was motor control, and it became associated with language before language became the primarily vocal thing it is for most of us today.

      What exactly Hopkins new data is, and what exactly he's arguing it shows, I honestly can't figure out from this article though. It's not even clear to me whether he's saying he has more evidence that Broca's is primarily a motor control centre, rather than a language center, or if he's found an association with another part of the brain entirely. I am looking forward to reading his actual paper.

      • links (Score:3, Informative)

        by Anonymous Coward
        Hi there.

        I got sent a link to your post from a friend who knows I do some research into hominid handedness and laterality. I was interested in reading the articles and managed to find them through the power of the internet, so I thought you might want the link: ec ember_2004/bne1186.html

        Cheers, Lisa
  • by IainMH ( 176964 ) on Tuesday December 07, 2004 @06:50AM (#11016283)

    *extends left hand*
  • by GuyFawkes ( 729054 ) on Tuesday December 07, 2004 @06:50AM (#11016284) Homepage Journal
    i fact just about every creature in nature and everything in nature has "handedness"

    only a "scientist" could attribute this to something recent like language skills.
  • by Nine Tenths of The W ( 829559 ) on Tuesday December 07, 2004 @06:54AM (#11016296)
    Since when has evolution* purposely chosen to do anything

    *In case there are any Americans reading, so as not to offend I'll include the standard disclaimer that evolution is just a theory and it's equally likely we were created out of mud 6000 years ago and fossils are the result of God's sense of humour.
    • Replace Americans with Alabamains and you are closer to the proper stereotype. Seriously, nut jobs that want to convince you that something like an evolutionary process exist in almost any country, not just the States.
      • True. However, in most countries they don't approach 45% of the population. []
    • "*it's equally likely we were created out of mud 6000 years ago and fossils are the result of God's sense of humour."

      Heh. If one were to debate with you, they could point out that the oil we have to day has.. pardon the experession.. fueled a lot of conflict that started at the turn of the millineum.

      I only bring that up playfully. ;)
  • "Purposely"? (Score:4, Insightful)

    by JaredOfEuropa ( 526365 ) on Tuesday December 07, 2004 @06:59AM (#11016319) Journal
    And evolution has purposely kept them.
    That sounds like evolution is something that deliberately picks what it thinks are good traits, and then decides to keep them around. In other words: God :)

    Perhaps left-handedness doesn't have any advantages, but no drawbacks detrimental to survival either. That too would allow it to remain in the 'gene pool'.
    • Re:"Purposely"? (Score:4, Insightful)

      by dave420 ( 699308 ) on Tuesday December 07, 2004 @07:22AM (#11016394)
      In the same way that gravity purposely decides what's balanced, and what will topple. You can call it God if you want, I just call it well-documented and well-researched science :)
      • "In the same way that gravity purposely decides what's balanced, and what will topple."

        Doubtful as gravity's goals don't change like evolution's does.

        Don't get me wrong, I understand your point. But likening evolution to physics is a bit uneven. I mean, name something other than evolution that strives to become better or more advanced. Gravity? No. It just sits there attracting mass.
        (Note: I'm not trying to 'debate and be right' with my post here. Rebuttals invited and considered. I'm feeling open
        • Re:"Purposely"? (Score:3, Insightful)

          by dave420 ( 699308 )
          Evolutions goals don't change at all - I don't know where you got that idea from. Evolution is a process. The process is continual. It's just the materials which get processed that change...

          Evolution strives as much as physics does - that is not at all. Both happen as a result of the physical makeup of the universe. Their "goals" remain the same - as goal of multiplication remains the same, as does that of subtraction :)

        • Re:"Purposely"? (Score:3, Insightful)

          by Scarblac ( 122480 )

          Doubtful as gravity's goals don't change like evolution's does.

          Evolution is just the phenomenon that if the exact genes of individuals can drift a tiny bit over the generations, and if some sets of genes tend to produce more offspring than others, you end of with more of one type than another over a long time.

          It doesn't have "goals".

    • Not to flame but, like, that's possibly the weirdest interpretation of God that I've even come accross.
      God=the Creator, fair enough.
      God=Quantum uncertanty, plausable.
      God=The big bang and that's it
      God=Picks and chooses what happens to us in our everyday life, compleatly against everything that I know! (well maybe I just don't know God), I know in the bible that Satan sat on one side and The Angel gabrail on the other, and the whole if you left eye causes you to sin then pluck it out stuff, but
      • Yeah, the scissors problem is annoying for us southpaws. (For all you rightys wondering what I mean, take a pair of 'ambidextrous' scissors in your left hand and cut about 8 inches into a piece of cardboard with them. It tried to gouge the flap of skin between your forefinger and thumb, didn't it? That's the scissors problem.) But I digress.

        Having to think in a slightly different way is a good thing though. It means that not everyone approaches problems from exactly the same angle. Groupthink is almos
    • That sounds like evolution is something that deliberately picks what it thinks are good traits, and then decides to keep them around. In other words: God :)

      God is not what decides somethings evolution... Things higher up on the food chain do :P
  • by Anonymous Coward
    ...must be difficult to find lefthanded bananas
  • by The Dodger ( 10689 ) on Tuesday December 07, 2004 @07:06AM (#11016343) Homepage
    First time I've heard of IT helpdesk staff actually doing anything useful...


  • by Nine Tenths of The W ( 829559 ) on Tuesday December 07, 2004 @07:06AM (#11016346)
    To suggest that left handedness is genetic is a socialist lie. It is condemned in the Bible, like being crippled and eating shellfish. Everyone knows that left handedness is a choice, a sinful lifestyle promoted by Satanic liberals. Even the scientific term, sinister, reveals it's Luciferian origin. Concerned parents must act now to stop children being taught to be left handed in schools, and to stop the media being overrun by positive depictions of left handedness. Would you want your child to be fondled by a left handed pedophile coming home from a sickening Sinster Pride march?

    Order a copy of "What Liberals Don't Want You to Know about the Left Handed Agenda", by Salvation Publications, for only $99.99. Comes with guaranteed promise of Heaven and a free shotgun.
    • I know this is a troll, but somebody went and modded it up I feel compelled to respond. Which was probably the point, so I'm a loser.

      Even the scientific term, sinister, reveals it's Luciferian origin.

      Sinister is derived from Latin, and means "left." That's all.

      • by Triskele ( 711795 ) on Tuesday December 07, 2004 @09:54AM (#11017248)
        Sinister is derived from Latin, and means "left." That's all.

        [Sigh] And it's use by the mediaeval church is why it means 'evil'. In fact although the parent was satire (not troll) as all good satire it was very close to the truth. The church has long used 'left' to mean 'evil' - left-handers really were persecuted in times past. We still use the phrase cack-handed. And a lot of the modern left-wing demonisation by the right is very religiously inspired.

  • by bloodredsun ( 826017 ) <> on Tuesday December 07, 2004 @07:12AM (#11016359) Journal
    This is an interesting study but I'm not sure how relevant it is.
    Humans have several areas of the brain where structure and therefore function differ vastly from other primates. Specifically the areas of the brain dealing with speech (Broca's and Wernicke's areas) and the connection between the two (arcuate fascicus). These areas have a definite correlation to handedness as a right-handed person has a 97% chance of having these speech structures on the left versus the right while in a left-handed person has a 50-50 chance of this (if my neuroanatomy is correct). This is why speech mapping must be performed on patients who will undergo neurosurgery near possible speech centres, for example in a temporal lobectomy.
  • by teamhasnoi ( 554944 ) <.teamhasnoi. .at.> on Tuesday December 07, 2004 @07:21AM (#11016386) Journal
    My puzzling habit of throwing my poop with my left hand is one step closer to being explained!

    Thank you, science monkey!

  • by smacktits ( 737334 ) on Tuesday December 07, 2004 @07:37AM (#11016446)
    I'm ambidextrous, and I'm in MENSA. Admittedly I was forced to learn to use my left hand while taking several years to recover from an injury to my right hand, so it's not 100% natural. Does that count?

    It's fun to be writing something in front of someone who doesn't know, and switch hands and continue perfectly. The look on their faces is priceless ;)
    • by dJOEK ( 66178 ) on Tuesday December 07, 2004 @07:48AM (#11016484)
      why do mensa members feel the need to constantly plug that fact?

      The fact that you're in mensa really has nothing to do with being ambidextrous.

      I suggest you try therapy, since you obviously have some problems to adapt to society, and it might wipe that smug "I'm-smarter-than-you" grin of your face

      And try using your capabilities for something useful, other than doing monkey tricks with your writing. they're really only feeble attempts to make other people feel inferior, and hardly impress other intelligent people.

      find a cure for cancer, then come back to brag
    • ... was to have you undergone brain scans before, during, and after your 'retraining'. A comparison study of language regions of the brain with motor skill manipulation may shed some light on why you're in MENSA.

      After all, wouldn't it be humorous to learn that your right handed injury granted you more intelligence since the neurons in another area of your brain were forced to more mundane tasks? :)
  • by j.leidner ( 642936 ) <> on Tuesday December 07, 2004 @07:52AM (#11016501) Homepage Journal
    ...I recommend the following two things:
    • in London, there's a shop called 'All things left-handed'; they have special scissors for left-handed people and other hillarious items
    • there's a great book about laterality called 'Left Hand, Right Hand' by Chris McManus (nomen est omen -- the Latin for 'hand' is manus ;-). Here's the Website of the book: click me []

    Try Nuggets [], the natural-language SMS search engine. Answers to your questions per SMS in 10 seconds.

  • by Anonymous Coward
    Interesting article though I disagree with the statement about LH persons being less analytical.

    I'm a third gen lefty (tree: PGM, F, myself). My eldest son fell from near my side of the family tree and he (now 6) has only ceased to be ambidexterous in the last two months. He went to the dark side and uses his right hand to throw and write. Still bats and kicks left however so maybe he'll make it to the major leagues yet. Still holding out hope for the newborn daughter.

    Anyway, I'm PhD physicist, my Dad
  • I'm a leftie. The reason I think left handness exists is specialisation. Darwinian theory doesn't mean we will all be the same exact highly optimised beings. What happens if the environment changes? Evolution would not be able to react fast enough. Instead sucessful groups of our ancestors, the ones which survived, emerged from the jungle and ultimately produced us, had group members with different strengths, different abilities. It's like any game, for example it red alert or d&d. If you only have spel
  • by kahei ( 466208 ) on Tuesday December 07, 2004 @08:28AM (#11016644) Homepage

    Evolution is not a god that sits on a mountain somewhere. It's the theory that those forms that have the greatest tendency to propagate in a given environment gradually become more frequent in that environment(*).

    Seriously, this kind of bizarre 'science as voodoo' thinking is why to a lot of people creationism doesn't sound so stupid -- "God wanted there to be left handed people for his own ineffable plan" sounds about equivalent to "Evolution has kept left handed people on purpose".

    It sucks and requires a certain amount of discipline, but it's better to keep science as science, a methodology for choosing between theories, than to let it become just another set of beliefs, like a religion.

    (*) I know this is not a good or rigorous definition of evolution in general or biological Darwinian evolution in particular, but throw me a frickin' bone here.
  • by Tim C ( 15259 ) on Tuesday December 07, 2004 @08:40AM (#11016689)
    Evolution hasn't purposely done anything. For whatever reason, there is not sufficient evolutionary disadvantage to being left handed for it to have died out amongst humans. Conversely, any advantage there may be to being right-handed is sufficent to make it dominant, but insufficient to wipe out left-handedness.

    Evolution is a name for a process, not a thing, it doesn't do anything, on purpose or not.

    For a geek/tech site, we're very loose with our terminology and language at times...
  • by jeffkjo1 ( 663413 ) on Tuesday December 07, 2004 @08:59AM (#11016757) Homepage
    1. Jim Henson
    2. Half of the Beatles (The half that still walks on this earth)- Paul and Ringo
    3. Ross Perot
    4. Henry Ford
    5. Joel Hodgson
    6. Jay Leno
    7. Matt Groening
    8. Mark Twain
    9. Michelangelo, Raphael, Leonardo (The painters)
    10. Don Adams

    The list goes on here. []
  • by museumpeace ( 735109 ) on Tuesday December 07, 2004 @10:04AM (#11017329) Journal
    We all have a brain and most of us have two hands so I guess that qualifies all of us to report anecdotal evidence and extrapolate.
    But chimp research would have to null out the contributions to handedness that might be made by any number of OTHER differences in brain development between humans and the rest of the primates before these scientists, let alone a bunch of /. readers could draw conclusions:.
    1. The timeline of human brain development from birth to adolescence is hardly one of linear increases in all capabilities and is not the same as chimps
    2. the LACK of parity between LH and RH dominant individuals is complex: the numbers are not evenly distributed but that is obscured, as serveral posters reported, by cultural enforcers that mask biologicaly determined behavior. We might even be seeing the reports of apparent intellectual advantages in a few lefties because our culture has beaten the lefthandedness out of a larger subset of the population with only the more gifted and adaptable surviving the brainwashing.
    3. ...These areas have a definite correlation to handedness as a right-handed person has a 97% chance of having these speech structures on the left versus the right while in a left-handed person has a 50-50 chance of this (if my neuroanatomy is correct)....[bloodredsun's comment] is particularly interesting since it implies there are yet other dimensions to the asymmetry between LR and RH dominance, these are not distributions of capability that are anatomically just mirror images of each other but distinctly different wiring.
    4. I have not read every comment but so far there is no report of data correlating extent of corpus collosum [CC:the bridge between L and R hemispheres. nearest analog to a computer bus you will find in brain anatomy] to handedness. The CC is [if memory serves] is better developed in women than men ON AVERAGE and women [perhaps as a consequence] have [on average] less rigid specialization of functions to particular brain regions. This is why [on average] women recover more fully from strokes then men do.
    5. someone probably trotted out the stat that lefties have more accidents and I just missed it. Its a whole other debate about whether that is due to strong tendencies to put the saftey/kill-switch/brakes/etc on dangerous equipment where a RH person would expect them or due to other considerations but its not likely to be attributable to language skills...differences between LH and RH persons that don't stem from language either support or don't repute the findings of the article so I guess this one is a point for the sciencists.
    6. Is there any study or known correlation between handedness and [_]dyslexia, [_]ADD or ADHD, [_]Stuttering, [_] other developmental anomalies, e.g. autism?
    But, of course, I have my anecdotes too;)
    My mom reports that she was probably a lefty but growing up in the 30's in a Missouri village where the dogs barked in German and you were either a Luthern or a Methodist, she had that bad habit beaten out of her. One of my boys writes [illegibly] with his left hand but throws [and I mean quite athletcally: he's an ultimate frisby player] righty.
    and PLEASE, if you can't read or react in an informed and rational way concerning the general fact that there are differences between men and women, please exit the conversation NOW!.

The unfacts, did we have them, are too imprecisely few to warrant our certitude.