Redundant design
August 18, 2007 6:22 AM   Subscribe

Wonder what that palmaris muscle is for? Turns out we humans have a whole bunch of spare parts.
posted by salishsea (13 comments total)

This post was deleted for the following reason: This is one of those vestigial posts. -- cortex



 
Amazingly, I was reading about this in Descent of Man just last evening. Yeah, that's what I do on a Friday night.

"The same muscle varies in many ways: Prof. Macalister describes no less then twenty distinct variations in the palmaris accessorius."

"The muscles are eminently variable: thus those of the foot were found by Prof. Turner not to be strictly alike in any two out of fifty bodies."

"...not one body out of thirty-six was 'found totally wanting in departures from the standard descriptions of the muscular system given in anatomical text books.'"
posted by neuron at 6:35 AM on August 18, 2007


...we humans have a whole bunch of spare parts.

Another group of interesting "spare parts" are the pseudogenes, chunks of our DNA that have become inactivated. My favorite is the one for GLO, the enzyme that makes vitamin C. It's absent in humans and in just a couple of other mammal species.

Once upon a time, the gene or its regulatory mechanism mutated such that the gene didn't work anymore. The affected ancestor was getting vitamin C in its diet, so the loss didn't hurt it. The gene is still there in our DNA, mutated just enough to be nonfunctional but the sequence is still easily recognized.
posted by neuron at 6:53 AM on August 18, 2007


“useless, or nearly useless...”

Perfect description of the human species and their vile meat eating ways.
posted by Gnostic Novelist at 6:56 AM on August 18, 2007


I wonder about the one comment in the link re: wisdom teeth, where it says "Only about 5 percent of the population has a healthy set of these third molars."

How is "healthy" defined here? I ask because many dentists here in Canada are in the habit of removing wisdom teeth just on principle "in case they cause a problem." My dentist assured me they'd be very painful later unless I had mine pulled - 15 years later, not a problem. I suspect a lot more are removed for the health of the dentist's wallet too.

Other than that, interesting post.
posted by Zinger at 6:57 AM on August 18, 2007


Interesting post. Ebay here I come!
posted by LarryC at 7:06 AM on August 18, 2007


Maybe it's because I just woke up, but the sentence "Surgeons harvest it for reconstructive surgery" creeped me out.
posted by L. Fitzgerald Sjoberg at 7:12 AM on August 18, 2007


"Intelligent design"--my ass.
posted by Kibbutz at 7:15 AM on August 18, 2007


I understand that Klingons have an entire spare spinal cord.
posted by nax at 7:17 AM on August 18, 2007


Well, that's one new optional anatomical feature I've discovered I have before breakfast. Excellent.
posted by phooky at 7:17 AM on August 18, 2007


Just three weeks ago my mom had the mechanics of her thumb rebuilt using that selfsame tendon. She's not playing "Rhapsody on a Theme of Paganini" yet but the x-rays showing the before and after are pretty amazing.
posted by rleamon at 7:23 AM on August 18, 2007


I can't wait for science to be able to turn that vitamin C gene back on, plus a bunch of others. Also, I'd like super memory, wings and a pony.
posted by DU at 7:30 AM on August 18, 2007


It's a double.
posted by CitrusFreak12 at 7:45 AM on August 18, 2007


Vestigial structures are not really "spare parts" or "redundant" if they are useless. A better example of redundancy in humans is having two kidneys.

The gene is still there in our DNA, mutated just enough to be nonfunctional but the sequence is still easily recognized.

Too easy in fact. This means that people who identify genes in the genome have to take extra care that they aren't calling something a gene when it's actually a pseudogene.

I can't wait for science to be able to turn that vitamin C gene back on, plus a bunch of others.

I'm not sure that it's really worth it for gene therapy—seems like it would be easier to just drink some orange juice every day. More fun too, if it's good orange juice.
posted by grouse at 7:47 AM on August 18, 2007


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