Chimpanzees Shed New Light on Hand Preference

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.'"

Comments

... evolution has purposely kept them ...

[andorsch]

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?

Re:... evolution has purposely kept them ...

[Bwian_of_Nazareth]

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.

Re:... evolution has purposely kept them ...

[nickco3]

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.

Re:... evolution has purposely kept them ...

[YouHaveSnail]

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.

Re:... evolution has purposely kept them ...

[Have Blue]

"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!"

Re:... evolution has purposely kept them ...

[WormholeFiend]

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 :)

In Unreal 2004, you can choose one of three positions -- left, right, or middle.

However, the game manual does not explain what body part you use to hold the weapon if you choose the "middle" position.

From the its-bloody-obvious-department

[physicsphairy]

"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!

Re:From the its-bloody-obvious-department

[Arker]

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.

I for one welcome our new left-handed overlords

[IainMH]

*extends left hand*

Re:!tsop dednah tfet tsriF

[mccalli]

HE shouldn't have been using the devil's hand in the first place

You Sinistromanualist, you...

More seriously the, errr, granparent post is referring to this happening to his grandfather. Minus the beating, this was still happening to me when I was at school in the eighties (UK). An English teacher made a concerted effort to force me to be right-handed, and it completely messed up my writing. You can see a clear difference between the schoolbooks I had before her 'teaching', and those I wrote afterwards.

For the worse, of course.

Cheers,
Ian

Evolution wants to be anthropomorphised?

[Nine Tenths of The W]

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.

Re:Evolution wants to be anthropomorphised?

[TheRaven64]

Consider the two options:

1. Create people and animals by waving your hands and saying `let there be stuff'
2. Create an incredibly simple system in which a combination of seemingly random events give rise to the evolution of consciousness.

Personally, I'd have more faith in a God who did the second - it's far more elegant - any God that opts for option 1 clearly has no sense of style. Assuming the existence of God, I'd say that belief in creationism is rather insulting to said being.

Re:Evolution wants to be anthropomorphised?

[kahei]

As a christian, I strongly agree.

It's ridiculous to suppose that God would have created a whole universe and then expected us to restrict our examination of it to a short list of statements.

And in Victorian times, everyone used to think the same way; the business of a scientist(*) was to admire, analyse, and better appreciate God's creation. Then the ****ing Evangelicals came along and it all went straight to heck.

(*)Except Frankenstein.

Re:!tsop dednah tfet tsriF

[TheRealSync]

nor am I a member of Mensa unforunately

Actually we had a poll on the members only section of our local mensa chapters website regarding this exact question - the conclusion being that we didn't have an unusually high (or low for that matter) number of lefties.

"Purposely"?

[JaredOfEuropa]

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"?

[dave420]

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 :)

Re:dude, read the bible

[krymsin01]

Yeah, well it's BUSH'S fault that he can't READ.

Re:I had never heard of this

[DataCannibal]

Nothing to do with handedness, that's just the way wome are. You'll realise that as you get to know more of them :-)

It's a preference, and is condemned in the Bible

[Nine Tenths of The W]

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.

Re:"Chimpanzees Shed New Light..."

[Nine Tenths of The W]

That's an outrageous comparison. Chimpanzees are capable of using simple tools and learning from their mistakes.

speaking from the midline

[bloodredsun]

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.

Re:i am left handed and yes...

[TheRaven64]

I'm ambidextrous. I'm better than both of you.

What about ambidextrous?

[smacktits]

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 ;)

Re:What about ambidextrous?

[dJOEK]

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

Re:!tsop dednah tfet tsriF

[NanoGator]

"One strange thing I've noticed when teaching and attending Emergency Medical Services (read 'ambulance service') classes is that there are a higher number of lefties then the general population."

It's a lot harder to run with left-handed scissors than the general populace realizes.

" And evolution has purposely kept them."????

[kahei]

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.

Holy anthropomorphisation!

[Tim C]

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...

My Dog's Got a Name and It's Oscar Mayer

[The-Bus]

While helping my girlfriend with her lab on the common Fiddler crab (Uca pugilator) I decided to do some side-research of my own*. I found that approximately 1/3rd of Fiddler crabs in our population (of about 20) were left-handed (in that their left claw was freakin' huge). This would lead credence to an earlier post talking about handedness being a surprise to rivals.

It is interesting to see, however, that the Scientific American article covering the same subject seemed to focus more on the study whose results found similarites in the limbic system asymmetry between primates. The handedness study (which of course waters down easier for the average person) seemed to be second fiddle.

By the way, the actual studies are found here (in 300-500KB PDFs):
Asymmetries in the Hippocampus and Amygdala of Chimpanzees
Handedness in Chimpanzees (Pan troglodytes) Is Associated With Asymmetries of the Primary Motor Cortex but Not With Homologous Language Areas

* I had previously determined that the bisque turned out a bit stringy and that scampi was preferred. This, sadly, derailed the other, more "important" research.

links

[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:

http://www.apa.org/journals/bne/press_releases/d ec ember_2004/bne1186.html

Cheers, Lisa

Re:It's a preference, and is condemned in the Bibl

[Triskele]

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.