
Sensorimotor Mechanics of People with a Sixth Finger - sohkamyung
https://digest.bps.org.uk/2019/06/12/breakthrough-investigation-of-people-with-a-sixth-finger-has-implications-for-infant-medicine-and-cyborgs/
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m463
The interesting technology of ctrl labs:

    
    
      https://www.ctrl-labs.com/
    

will give "common five fingered" individuals the ability to catch up.

They use machine learning to decode the nerve impulses in the arm, so you can
play video games without moving and can let you synthesize "extra" arms.

search "ctrl labs" and watch the youtube videos, some of scifi possibilities
are very interesting.

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Causality1
>suggest that it may be of value to augment normal five-fingered hands with an
artificial supernumerary finger

That's missing the big picture in my opinion. This research indicates the
human brain is capable, all on its own, of adapting to entirely new
sensorymotor functions. Think of the implications. If some type of new
functionality were grafted onto you, you'd be able to control it without
having to "reassign" any of your current functions. You could move a "third
hand" cursor around in three dimensional virtual space as if it were a virtual
body part, not just an interface you have to consciously manipulate like a
mouse or keyboard.

~~~
Swizec
> not just an interface you have to consciously manipulate like a mouse or
> keyboard

How conscious is that really tho? I don’t think about how to type, I just
think thoughts and they come out on the screen. It’s about as conscious as
speaking.

Same for the mouse. I don’t think about the mouse consciously, I just look at
an item on the screen and choose to interact. Like grabbing a glass of water
with my hand.

~~~
causality0
Now matter how perfect it is, it is by definition less perfect than the
movement of your hand itself. The real world is also limited by inertia, which
virtual interfaces are not if they bypass the hands entirely. We're a long way
from developing really good brain-computer interfaces, but this finding means
we have just a little less groundwork to lay.

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m-i-l
I remember reading (a long time ago so can't provide a reference) that in
1000s of years most humans would have an extra finger. I'd assumed that this
was because of the evolutionary advantage it would have given their forebears,
although I would question how much natural selection applies to rational
beings like humans these days. But on a quick bit of reading now, it seems
like it could be because it is a dominant trait. Although after a bit more
reading, it seems it might not become more common over time due to the Hardy-
Weinberg principle[0].

[0]
[https://en.wikipedia.org/wiki/Hardy%E2%80%93Weinberg_princip...](https://en.wikipedia.org/wiki/Hardy%E2%80%93Weinberg_principle)

~~~
dTal
I know it was just an aside, but I can't let this go:

>I would question how much natural selection applies to rational beings like
humans these days.

It's a universal principle, why wouldn't it apply? Each generation is composed
of the offspring of those members of the previous generation who reproduced,
introducing a statistical bias. Why would it be different "these days", and
what has rationality got to do with it?

Besides - as for the notion of 'rational' humans, especially in the context of
sex and reproduction - I'll get my coat.

~~~
TeMPOraL
> _It 's a universal principle, why wouldn't it apply?_

Because ever since we've invented writing (and arguably even before that -
ever since we've invented spoken language), we've left the domain of
biological evolution. We now accumulate, evaluate and discard knowledge and
technology couple orders of magnitude faster than natural processes. From
nature's POV, the entire ~10k years of human civilization happened in a blink
of an eye (and note that all the interesting things happened arguably in the
last couple hundred years).

~~~
marcoperaza
There is still differential production of offspring who produce offspring. The
selection is against kind of people who have few children or have few children
who go on to have children themselves. That’s how it always has been and
always will be unless we abolish natural reproduction.

~~~
TeMPOraL
Again, whatever effect this selection has (with quantized increments of the
length of a generation), it's completely drowned in memetic and technological
evolution(s) which currently operate at the speed of Tweet. In your particular
example, this arguably derails biological evolution completely - the decision
to have kids, and how many kids to have, is dominated by economic and
(secondarily) cultural considerations, which change significantly between
generations. Evolution will have hard time identifying genes to promote, when
the minimum unit of change is probably "how smart people are" or "how social
people are", both having many more reasons for being favoured by natural
selection.

~~~
marcoperaza
It’s a messy process, and we may not be able to see where it’s going, but you
can bet that there will be changes in human phenotypes and their prominence
over the course of many generations.

> _Evolution will have hard time identifying genes to promote, when the
> minimum unit of change is probably "how smart people are" or "how social
> people are", both having many more reasons for being favoured by natural
> selection._

If I understand you correctly, that’s just not true. In his seminal work, _The
Selfish Gene_ , Richard Dawkins showed that the individual gene is the unit of
selection. A genotype that tends to result in a slightly stronger preference
for a family life is exactly the kind of thing that could become more
prominent, even within one or two generations. I’m sure this is happening
right now.

> _In your particular example, this arguably derails biological evolution
> completely - the decision to have kids, and how many kids to have, is
> dominated by economic and (secondarily) cultural considerations, which
> change significantly between generations._

I was not making a particular example at all. That is the function of natural
selection: it selects for the genotypes had by those who have children who go
on to have children themselves.

The selection doesn’t have to happen at the level of a preference for kids. A
gene related to diligence or conscientiousness or just about anything else can
have effects that ultimately cause differential reproductive success for you
and your offspring.

The fact that it’s all too complicated for us to model has bearing on it at
all.

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curioussavage
A bunch of my Wife's cousins all had 6 fingers. They had them removed after
birth.

~~~
eps
From what I read, _fully-functional_ and _fully-formed_ sixth fingers are
exceedingly rare. More often than not they are neither. They just interfere
with daily life and attract unwanted attention.

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anon1253
Ever since I was a child I had this strange idea that I was missing fingers (I
have 10 like most). From grade school till middle school I even kept counting
them as if something was amiss. I mean, it's not like it's actively bothering
me or something, but just a bit of a curious quirk: I think I should have 12
fingers. Although in my case it feels like they should be to the side of my
pinky, not between the index and thumb. As far as I know my parents didn't
have them removed at birth either. Funny enough I believe the gene for it is
even dominant (meaning it needs only one copy to express the phenotype), it's
just not very common in the general populous.

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timbit42
It would be more useful to have another arm or two.

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dx7tnt
Is there anyone on HN with 6 fingers? How's your typing? Seems like it could
only be a benefit on a keyboard.

~~~
baxtr
Not quite typing, still insightful. A video from the original paper the
article refers to: [https://static-
content.springer.com/esm/art%3A10.1038%2Fs414...](https://static-
content.springer.com/esm/art%3A10.1038%2Fs41467-019-10306-w/MediaObjects/41467_2019_10306_MOESM5_ESM.mp4)

~~~
inflatableDodo
That's a really cool video, is interesting to experience how much my vision
tries to reject the extra finger. Is hard to explain exactly, but every time
the hand is held in a way that hides fingers, then my brain goes back to
predicting it as a standard hand, then pops back to six digits again when all
fingers are visible.

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aetherspawn
Sounds like 5 fingers is the mutation!

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arethuza
Isn't every feature of every living thing the result of a mutation?

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ObscureScience
Ofcourse. But I wonder wonder if the sixth finger arose in humans or if it's
an expression of an previously common structure that has been suppressed for
the last couple of million years. I would wager on the latter.

~~~
duskwuff
It's an anomaly. Look at the analogous structures in other vertebrates -- in
species where digits are discernable (i.e, discounting mammals with hooves or
without front limbs at all), there are practically always five. Even a
structure as unusual as a bat's wing is made up of five "fingers".

~~~
mkl
Losing digits seems relatively easy - that's where hooves come from (horses
have one toe left, goats two). It's gaining digits that seems very hard. It's
possible that some configuration of six fingers could be better, but we
probably can't get from our local optimum to that without going through major
disadvantages. Apparently five has been the maximum number for most creatures
for 420 million years:
[https://www.reddit.com/r/askscience/comments/1org2e/why_do_m...](https://www.reddit.com/r/askscience/comments/1org2e/why_do_most_mammals_have_5_fingers/)

