Finger lickin' cool

June 4, 2019 3:34 PM

Supernumerary fingers (polydactyly) are often considered to be a useless malformation and are usually removed at a young age. In this Nature Communications article (Open Access), two people with polydactyly are shown to coordinate the extra finger with their other fingers for more complex movements than five fingered subjects, and to carry out with only one hand tasks normally requiring two hands. And they were also able to play a video game designed for 6-fingered people.

The exceptional manipulation abilities in our polydactyly subjects suggest that it may be of value to augment normal five-fingered hands with an artificial supernumerary finger. For several years, roboticists have been attempting to develop extra limbs to augment human movement abilities and neural interfaces to control them. The biomechanics and functionality of the polydactyly hands analyzed in this paper may be used as a blueprint for the development of robotic hands.
The article provides supplementary downloadable videos, ; some of these videos are embedded here.

posted by elgilito (23 comments total)

Reminds me of this scene from Gattaca.
posted by Sangermaine at 3:39 PM on June 4, 2019 [3 favorites]

I love how society is rethinking the assumptions about disability.
posted by agregoli at 4:08 PM on June 4, 2019 [5 favorites]

Also useful for murdering fathers of Spaniards.
posted by Pastor of Muppets at 5:15 PM on June 4, 2019 [16 favorites]

Antonio Alfonseca probably had a better career as a major league pitcher because of his six fingers on each hand, not in spite of it. Supposedly, his trademark sinker was only possible because the extra finger on his hand.
posted by jonp72 at 5:19 PM on June 4, 2019 [5 favorites]

I do find it odd that it is standard to remove extra fingers, without seeing if they are functional. Sometimes they don't have complete bones or are otherwise going to interfere with good hand function, but if it's a working finger why would you operate on a child?
posted by tavella at 6:22 PM on June 4, 2019 [10 favorites]

And they were also able to play a video game designed for 6-fingered people.

Guitar Hero?
posted by Faint of Butt at 6:42 PM on June 4, 2019 [7 favorites]

what if someone made a sword for six fingered people?
posted by mulligan at 8:56 PM on June 4, 2019 [2 favorites]

but if it's a working finger why would you operate on a child?

Because Hannibal Lecter (in the book Silence of the Lambs) canonically has "mid ray duplication polydactyly" -- a duplicated middle finger. He eventually (in Hannibal, he eventually removes it surgically to be less conspicuous).

Best not to take chances.
posted by ricochet biscuit at 8:57 PM on June 4, 2019 [1 favorite]

why would you operate on a child

Because unfortunately any kid who looks ‘strange’ will suffer from adverse and unwelcome attention a lot. These decisions can’t be easy, but I entirely understand parents who think their kid is likely to be happier without all that.
posted by Segundus at 10:30 PM on June 4, 2019 [2 favorites]

Relevant kitten.
posted by sebastienbailard at 12:18 AM on June 5, 2019 [2 favorites]

I met quite a few people in Afghanistan with extra thumbs. From what I understand it is considered uncool there to modify God's work, so extra fingers or thumbs tend to be left as is.
posted by Meatbomb at 12:35 AM on June 5, 2019

If your cozy costal cliff-face cave dwelling is infested with jedi puffins, the Norwegian Lundehund is here to help.
posted by sebastienbailard at 2:19 AM on June 5, 2019

I'm so jealous, I would have love to have 2 extra fingers.
posted by SageLeVoid at 2:57 AM on June 5, 2019

I have an aunt and uncle who both had extra fingers at birth that were removed. Family lore says it was due to Mennonite ancestry and associated inbreeding.
posted by nestor_makhno at 3:06 AM on June 5, 2019

I met quite a few people in Afghanistan with extra thumbs.

I have extra thumbs, but sadly only in my brain.
It doesn't provide any extra dexterity, it just means I drop stuff more often when I forget and try to hold things with a non-existent thumb.
posted by Just this guy, y'know at 3:21 AM on June 5, 2019 [1 favorite]

I would like to be able to Ctrl-Alt-Delete with one hand. With only 5 fingers on each hand, I can't quite do it.
posted by Kirth Gerson at 3:35 AM on June 5, 2019 [1 favorite]

I was born with postaxial polydactyly on both hands. Had the extra digits removed soon after birth.

Don't have any photos, but same as this.

Both my hands work normally, and have normal symmetry and appearance, other than having somewhat slender fingers, and large palms compared to my normal length fingers (inverted palm-finger length ratio).

Gives me pretty good reach on a guitar. On a standard classical guitar I can hold the bottom F bass note at the first fret, and bar the top 3 strings at the 5th fret to make an F Maj7 chord (F-C-E-A). Much to the annoyance of my guitar playing friends. :-)
posted by Pouteria at 4:12 AM on June 5, 2019 [4 favorites]

Hax!

Seriously cool. Their thumbs are totally different, with a ball and socket joint instead of a saddle. Their next digit is a three-phalanges finger that looks like a pointer finger but has the thumb's ball and socket. Then the rest of the digits are completely mundane. This is the kind of hand I've always wanted; this or a saddle joint digit where my pinky is.
posted by Made of Star Stuff at 4:14 AM on June 5, 2019 [1 favorite]

nestor_makhno: Mennonite ancestry

Eponyhistorical.
posted by clawsoon at 5:34 AM on June 5, 2019 [2 favorites]

I'm fascinated by the brain's role in this. It's completely unfazed by the extra digit (or, in the case of us five-fingered folks, the lack of a potential digit). Extra digit to control? No problem, just gotta run a couple extra wires.
posted by clawsoon at 5:39 AM on June 5, 2019 [3 favorites]

I find it interesting that this family apparently has a stable, heritable form of polydactyly, which apparently provides considerable advantages in manipulation... yet the 5-digit form seems to be really intensely conserved across not just humans but primates in general. We don't even have the level of 'substantial subgroup has polydactyly' like cats or dogs. It really seems like this would be a great form of hand/foot for a primate.
posted by tavella at 9:17 AM on June 5, 2019 [2 favorites]

tavella: digit conservation is an extremely interesting and important question in evolutionary developmental biology. It's not just primates with five digits -- it's tetrapods. In cases where vertebrate tetrapods have fewer than five digits, it is due to loss of digits in the ancestor. Not only that, but digits are lost in a predictable order. Digit order is thumb= I, pointer=II, middle=III, ring=IV, pinky=V. That's the anatomical order based on humans, with your thumbs being "anterior"; it's not the developmental order. Digits develop middle-outward; developmental order is III, II, IV, I, V. And the evolution of fewer digits -- digit loss -- occurs in the opposite order* of development. Pinky first, then thumb, then ring, then pointer. Digit III is always retained unless the entire hand/foot ("autopod") is lost.

So in horses, just for example (previously), the hoof is the fingernail of digit III. Digits IV and II are retained vestigially in ancient horses/some other hoofed animals but completely lost or fused into the digit III in modern horses.

*I might have my order wrong; I'm not sure if II comes before IV developmentally or vice versa.

But "five digits" is the ground state of autopods not because humans have five fingers and five toes, but because of some evolutionarily conserved aspects of limb development. Digits condense from the developing limb bud based on the overlap of different protein gradients, and the size of the embryo's developing hand relative to its developing wrist helps determine that protein gradient, and just generally speaking, there's enough room for five or fewer digits, but not more than five.

Polydactyly seems to happen more often when the hands and feet get really big. Draft horses and Maine Coon cats are classic examples. In animal strains that are much larger than typical, it is mostly anecdotally observed, those paws just get big enough to stick an extra digit on 'em.

So, I'd assume that large stable populations of humans with polydactyly aren't observed for some combination of three reasons: 1) We don't inbreed enough to build up the whole suite of genes necessary for enormous body size and hand size, 2) Most of the time, any real advantages conferred by polydactyly are swamped by human (and primate) fear of aberrant forms and 3) As a corrolary of 1, we aren't likely to know much about groups where it is somewhat common.

OMG this is all so much speculation but it was really fun.
posted by Made of Star Stuff at 10:09 AM on June 5, 2019 [10 favorites]

initial reaction: GAH

ok, back to the video.

cool!
posted by numaner at 11:43 AM on June 5, 2019