Why do we have five digits on our hands and feet?
Why not six, or four?
According to the Scientific American, many millions of years ago some tetrapods – meaning
four-limbed creatures – had more digits, but as animals developed better wrist and
ankle joints the number of digits was reduced over a very long period of time.
Few animals have six digits, with the panda bear being a four-legged beast that stands
out from the crowd.
Humans and animals may be born with an extra digit or two, but this is the result of supernumerary
digits appearing as a result of a physical anomaly known as polydactylism.
Some people are born with fewer digits, and that is known as oligodactyly.
Today we’ll look at the strange case of our diverse digits, in this episode of the
Infographics Show, Why are our fingers different lengths?
We will get to the length very soon, but first let’s talk a bit more about why we have
five digits.
“We know that in the Devonian there were many [fish-like] tetrapods with different
digit ray numbers — five, seven, I believe up to 13 — but by the end of the period,
we had only pentadactyl tetrapods,” said a palaeontologist at Monash University (pentadactyl
means having five digits).
But he then went on to say no one is exactly sure why five became the magic number.
Science just tells us that’s the way we have evolved.
Four would be too few and six too many.
What makes humans the great manipulators of things we grab hold of are our excellent thumbs,
which give us more digit dexterity than our closest ancestors the apes.
We have something called the flexor pollicis muscles, which give us more control over our
thumbs.
In other primates this muscle is either absent or works in a very rudimentary way.
Apes can peel bananas, but we can carefully construct the internal organs of a highly
complex watch.
If you ever find yourself in the position of being told you have to lose a finger, you
might think you should probably opt to lose your little finger, or pinky finger to those
of you in the USA.
You certainly don’t want to lose your thumb, sometimes called ‘half of the hand” or
the index finger, as together these two digits do most of the work.
Saying that, just losing one finger will profoundly affect the strength of your grip.
Lose a thumb and life will get much harder.
Imagine trying to button-up a shirt, turn a key, play Playstation, write with a pen,
or even cut into a delicious steak without your thumbs.
Ok, let’s just imagine you’ve been kidnapped and in a moment of altruism your kidnappers
tell you that you can choose which digit you will lose first.
They also tell you if they don’t receive the ransom they are going to send more of
your digits.
A doctor interviewed by Business Insider says that people would often make the wrong choice
and go Yakuza-style and choose the pinky finger first.
Apparently, that’s the wrong choice.
She said that your most expendable digit is the first finger of the hand you don’t write
with.
She said if you lose that your second finger will compensate for the loss quite well, while
losing the pinky will affect the strength of your grip.
That outlier pinky can’t be compensated for so well.
Business Insider wrote, “The pinky is actually incredibly important, and it's a keeper.
Basically, the reason humans have ‘opposable’ thumbs — the springboard of our evolution
from being just another ape — is that the thing doing the most opposing is the little
finger.”
The New York Times wrote a story about this, too, called, “The importance of the pinkie,
experienced firsthand.”
This little digit provides lots of strength.
Try doing pull-ups and not using it and you’ll see.
As for toes, if the kidnappers have taken all your fingers, we are told the most expendable
digit is the fourth toe on the foot which you don’t use for kicking things.
By the way, if you want to keep all your fingers there are some activities you should be mindful
of.
The U.S. Consumer Product Safety Commission tells us the activities that cost people fingers
are wood-chopping, feeding paper shredders, chopping vegetables, working with industrial
machines and power tools, cleaning stuff out of your lawnmower and a biggie for younger
people, closing windows and doors.
Ouch.
Ok, so now let’s turn to the question asked in this show, why are these digits all different
lengths?
Well, not all fingers are made equal.
Some people do tend to have rather large hands and long fingers.
It’s quite complicated as to why some of us have bigger hands and longer fingers.
It’s generally thought that the ratio of your fingers is related to how much testosterone
fetuses are exposed to in the womb.
There are some pretty crazy studies out there.
One such study wrote, “The ratio of the length of the second finger, or digit, to
the fourth finger (2D:4D) is influenced by fetal exposure to androgens; a smaller ratio
indicates greater androgen exposure.”
Believe it or not, that study said that men with longer ring fingers than index fingers
(first finger) were more agreeable with women, and men with longer index fingers were more
likely to fight with females.
This isn’t pseudo-science by the way, these were serious studies led by scientists.
Other research shows that a long ring finger may lead to more risk-taking and better athleticism.
One study at Oxford University even said that if the ring finger is longer it may well lead
to the person being more promiscuous.
That’s both men and women, so maybe you should check out your partner’s hands today.
If you’re a promiscuous person you can always blame the testosterone.
“It wasn’t my fault, my exposure to hormones while in my mother made me do it.”
Case closed.
You might also just have big hands and big feet.
You could be big in general and so that’s normal, but you might also have excessively
large hands for your size.
That could just be hereditary.
Does the size of your hands correlate with penile size?
That’s the million-dollar question.
Live Science tells us that various studies have come up with different conclusions.
Once again, some studies tell us that more testosterone in the womb, larger ring finger,
bigger phallus.
But it’s not conclusive, and so don’t go judging a book by its cover.
So, you might have small hands for a big man.
You might have finger ratio differences.
But why are your fingers not all the same length?
Unlike other primates, as you know we have this marvelously strong thumb.
We also have shorter digits and a smaller palm.
Gizmodo talks about the “perfect opposability” of our thumb, meaning it can touch the tips
of each of our fingers with finesse or it can lock-on tight.
This gives us the ability to firmly manipulate objects and also tinker with things.
This is why we are the great tool makers of the animal world- well, that and our excellent
brains.
Millions of years ago our ancestors had the hands we see of modern primates: long and
strong fingers that were good for tree-climbing but not so good for threading a piece of cotton
through the eye of a needle.
Some scientists tell us our hands evolved in line with the tools we were making.
3.4 million years ago when we started making crude stone tools we didn’t need so much
dexterity, but later we refined our tools when we had better dexterity.
We only have that dexterity because our fingers are perfectly sized to oppose our thumb.
It wouldn’t make much sense to have a longer pinky finger, for instance.
But it wasn’t just about making tools, it was what we did with those tools.
We fought each other and we hunted.
To do that well we needed to have a very strong grip.
If you’re going to club your enemy to death you will need to be able to grab hold of that
weapon with a strong grip.
But we also have a precision grip, which is different.
When the person didn’t have a club lying next to him he might have picked up a stone.
The way we hold stones, or balls, or darts, is very different from the grip we employ
when holding an axe.
Scientists tell us it is this precision grip that really led the evolution of our different
sized fingers and how they work so well with our thumb.
Next time you’re up close to a chimpanzee hand it a stick and see how well it can manipulate
it without dropping it.
Better still, hand it a tennis ball and watch how much difficulty the chimp has keeping
hold of it.
We are kidding, don’t go near chimps, they might pull your fingers right off.
Ok, so we evolved with these hands to make complex tools and also to have strong grips
that are firm and precise.
So, why not just evolve to have even longer fingers and have more precision?
The Economist touches on this question and it seems the answer might be boxing.
Can you imagine Mike Tyson with long witch-fingers?
It wouldn’t work.
Long fingers as we have seen are good for climbing, but they are not good for making
a fist.
In fact, we don’t see monkeys getting into punch-ups, although that would be quite amusing.
A paper in The Journal of Experimental Biology by Michael Morgan and David Carrier of the
University of Utah tell us that our hands are the way they are not just because of grip,
or precision, or watch-making, but also because when we scrunch our fingers into a fist we
have a weapon already.
The scientists conducted an experiment with athletes, including boxers, in which they
were asked to hit a punching bag as hard as they could – both with an open palm and
with a fist.
They then asked the athletes to form badly made fists, such as with a pointed thumb or
the fingers laying flat on the palm and not dug right into it.
You won’t be surprised to hear that the properly-made fist delivers much more power
than any other way you can hit a punching bag.
We now have to acknowledge that it is only because we have varying finger lengths that
we can make this ideal fist.
This, with the thumb, creates the perfect storm of a stiff fist.
If a monkey tried to do it there would be a space between the fingers and the palm and
so its fist would not be anywhere near as powerful.
Before we started making tools or throwing stones we were heavy punchers, primitive pugilists
who didn’t have a spear to fall back on when the going got tough.
Can you add anything to this story of our hands and fingers?
Tell us in the comments.
Also, be sure to check out our other video: What Would Happen If You Only Drank Coke.
Thanks for watching, and as always, please don’t forget to like, share and subscribe.
See you next time.