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What's Right When You're Left?

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Jonathan Gottschall was just a lowly adjunct in the English Department of a small college outside of Pittsburgh. Then one day a mixed martial arts gym shows up across the street from his office. Jonathan can’t resist trying his hand in the ring, but 4 months into his training he’s stopped in his tracks by a southpaw and something called the Faurie-Raymond hypothesis. David Wolman, author of "A Left-Hand Turn Around the World" breaks in to dispel the popular myths surrounding left-handedness, and explain why people like him have managed to stick around in a right-handed world. And somehow, we end up in an art studio full of parrots.

Guests:

Jonathan Gottschall, Pat Walters and David Wolman

Comments [14]

Tom Cushing from Saline, MI

About your story on 'handedness' in parrots: While I have no actual scientific data to back it up, I believe 90% of parrots are also right-handed.
Consider; You are hanging from a pipe, far enough above the ground that you would be seriously hurt if you fell. You must reach for something. Wouldn’t you maintain your grip on the pipe with you dominant hand, and reach with your non-dominant?
Since parrots perch and reach with the same pair of 'hands,' doesn't it follow that they would grip the perch with their dominant, and reach with their non-dominant?
Jus' sayin'...

Jul. 08 2014 12:17 PM
Rick Evans from 02368

Tio Tony change Rafa from a natural righty to a tennis lefty. So much for genes.

Jul. 05 2014 03:57 PM
Ruth from Michigan


You discussed only handedness.

If you are right handed, you are usually right eyed. However, I wonder how many people are right handed and left eyed. When I was in the Air Force, we found that I was left eyed when I went to the firing range, they had to create an eyepatch for my left eye so that I could try to aim with my right eye.

Most point and shoot cameras were made for right eyed people. Digital cameras have made life much easier for left eyed people.

Also, left or right footed or left or right eared?

Jul. 04 2014 02:29 PM
kyle of Science did WHAT?! from NYC

I've only listened to this episode last night and, as much as I love radiolab, I couldn't help but think you should have included a chat with a geneticist or evolutionary biologist or genetic anthropologist. I completely agree with the comment by Brien Boru. There's were two things that struck me from the conversations in the podcast. One was the prevalence today of this misconceived notion about trait presence and selection. Evolution is funny sometimes because traits can continue on as long as there's no selective pressure AGAINST passing on those genes. It doesn't always necessarily mean there HAS to be some sort of advantage to passing them on.

The other thing that struck me, especially with the righty-writer friend who got KO'd out of his wits by the lefty boxer... Correlation does not equal causation. I refer you guys to http://tylervigen.com/ and the classic http://xkcd.com/552/ (roll over image please).

May. 10 2014 02:15 PM
TJG

A bit late, but I only just listened to the podcast. I think a trait must incur it's advantage or disadvantage before individuals reache reproductive age for it to be effected by natural selection. If it doesn't, it is just as likely to selected or eliminated as any neutral trait, no matter the magnitude of the advantage or disadvantage.

Apr. 07 2014 03:14 PM
paul burns from Los Angeles

A little clarification on a comment made by Jad. Left handed pitchers specialize in pitching to left handed hitters, nor right handed ones.

Mar. 20 2014 05:24 PM

You get knocked out after four months of training and write it off as a genetic advantage possessed by the left handed for millions of years? Train for another fifteen months.

Mar. 12 2014 07:11 PM
JA from Atlanta, GA

I think Jonathan is following the wrong path by ascribing Nick's physical dominance of him to the Faurie-Raymond hypothesis.

It's more likely as simple as this: Nick was the superior fighter.

Mar. 12 2014 03:55 PM
brienboru

In the discussion of left-handedness and evolution, there was an assumption that selective advantage was necessary to explain persistence of a phentoype. If you leave out selection pressure, the genetic frequency will be inherently stable under the general conditions of the Hardy-Weinberg equilibrium (http://anthro.palomar.edu/synthetic/synth_2.htm). So, to whatever degree left-handedness is influenced by genetics, one would expect it to continue in some proportion, even without a distinct reproductive advantage. Selection could be used to explain why right-handedness is the more dominant phenotype, but it really has no bearing on left-handedness not "going extinct".

Mar. 06 2014 10:25 AM
Hannah from London

Lefty high five to all my fellow lefties out there!

Mar. 05 2014 05:22 AM
Taylor

While there may not be conclusive evidence for increased fitness of left-handed humans in violence or athleticism, selection for rare handedness HAS been shown in some taxa.

In Lake Tanganyika, there are cichlids which eat the scales off of other fish. Some are "left" mouthed (eat the scales from the right side of other fish), others "right" (the inverse). It looks like when left-mouthed cichlids are common, right-mouthed individuals are better able to surprise fish. This is called "frequency-dependent selection", and was alluded to in your broadcast. Several publications on this topic have been published. Some examples below:

Hori (1993) Frequency-dependent natural selection in the handedness of scale-eating cichlids. Science. 260(5105): 216-219.

Lee et al. (2012) Handed foraging behavior in scale-eating cichlid fish: It's potential role in shaping morphological asymmetry. PLoS. doi: 10.1371/journal.pone.0044670

Mar. 03 2014 11:00 AM
amy

Think that you got the workings of evolution a bit wrong. Evolution, or natural selection more correctly, would not "select for diversity" just in case, it works by selecting FOR or AGAINST certain phenotypes (and indirectly genotypes), mainly by determining who passes on the most offspring. if being left-handed did not confer an advantage on its own, it would not be selected for. It is most likely that it does not confer a big DISADVANTAGE to the the people who carry the trait. Note that based on the genetics, it is likely that more than one gene is involved in handedness and that if even if you select against the people who express the trait, if there is no selection against the carriers who can transmit it, but not express it, the trait will remain in the population. The deleterious variants such as those causing Cystic fibrosis and Tay Sachs disease (just to name two) are still present in the population even though the affected people rarely reproduce. while I realize the none of your interviewees are geneticists, perhaps checking with someone who is would have been wise.

Feb. 27 2014 04:57 PM
donniedarko

In the segment about left handedness the connection between language and right handedness is made. But when another species, parrots who are predominantly lefties is mentioned, the question of brain structure is ignored. For anyone interested, the motor and language centers in the parrot, songbird and hummingbird brains are both located in the forebrain. Whether it is in the right or left hemisphere seems like the obvious question that was never asked.

As a side note depending on the species of parrot, they may be either right, left or ambidextrous. There is a strong correlation between larger size and being right/left footed or smaller and being ambidextrous.

Feb. 27 2014 03:28 PM
Amy from Washington, DC

Are we asking the correct question, with regard to Parrots? Are they lefties because they prefer to grab the chip with the left, OR - are they righties because they prefer to balance with the right foot while they grab the chip?

And on an unrelated-but-kind-of-related note, who can we talk to at Google to make Google Glass favor the left-eye dominant among us!?

Feb. 27 2014 12:09 PM

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