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.'"
Re:!tsop dednah tfet tsriF (Score:3, Informative)
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.
Re:Evolution wants to be anthropomorphised? (Score:2, Informative)
speaking from the midline (Score:4, Informative)
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.
To the laterality-interested... (Score:3, Informative)
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Re:... evolution has purposely kept them ... (Score:4, Informative)
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:From the its-bloody-obvious-department (Score:5, Informative)
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 [medterms.com] 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, [google.com] 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.
Re:... evolution has purposely kept them ... (Score:3, Informative)
Ferniehirst Castle [burkes-peerage.net], Wikipedia article [wikipedia.org]
(And yes, I am partly left-handed ;)
Re:... evolution has purposely kept them ... (Score:2, Informative)
links (Score:3, Informative)
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/
Cheers, Lisa
Re:It's a preference, and is condemned in the Bibl (Score:4, Informative)
[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.