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What is a Hitchhiker's Thumb?

I started taking piano lessons when I was six years old. Although I had long fingers for my age, I always had an issue with the keys in the middle of the keyboard. My thumbs never quite hit them the right way.

My thumb weirdness continued into other activities, with my hands not always working quite as I wanted. I was in high school before I learned why my thumbs seemed so different from everyone else's.

I had hitchhiker's thumbs!

How Does a Hitchhiker's Thumb Work?

Hitchhiker's thumb is a layman's term for distal hyperextensibility of the thumb.The joint closest to the end of the thumb is called the distal joint. In most people, the distal joint of the thumb allows the thumb to straighten and to bend forward (toward the palm of the hand). With a hitchhiker's thumb, the distal joint hyperextends, allowing the thumb to go beyond the straight position and point toward the back of the hand.

Basically, my thumbs not only bend forwards, but they also bend backwards. In my case, both bend ninety degrees backwards. So THAT's why using scissors was always so uncomfortable!

There are variations in the hypterextension of a hitchhiker's thumb. Some people can bend their thumbs backward but have limited flexibility going forward. Others, like myself, have a full range of motion in both directions.

A Hitchhiker's Thumb In Action!

A hitchhiker's thumb looks like this.
A hitchhiker's thumb looks like this.

Do you know anyone who has a hitchhiker's thumb

See results

A Recessive Trait

Let's address a bit of genetics when discussing how a hitchhiker's thumb happens, and why it is so rare.

As part of your genetic makeup, there is a gene that determines whether your thumbs are hyperextendable or not. We'll call this the "bendy thumb gene", for lack of a better term.

For each bendy thumb gene, there are multiple alleles. Alleles are the variations of a given gene that can exist. For example, one allele of the "bendy thumb gene" may produce a perfectly straight, "normal" thumb extension. Another allele of this gene may be a thumb that can bend backwards and forward at ninety degrees each way. The "bendy thumb gene" has a spectrum of alleles, from perfectly straight to bending all the way and everything in between.

Genes are inherited from your parents, and one of each type of gene is inherited from each parent. So, the each of us has two genes (one from Mom and one from Dad) that determine your thumb bending ability. Depending on what alleles you receive from your parents, your thumb could fall anywhere in the spectrum.

A hitchhiker's thumb is called a recessive trait. There are two general types of traits - dominant and recessive. A dominant trait comes from a dominant allele, which means it overpowers any other allele with which it is paired and is the allele that is displayed. A straight thumb is dominant, so anyone with a straight thumb allele, regardless of their other allele, will have a straight (non-hitchhiker's) thumb.

A recessive trait comes from a recessive allele. In fact, in order for a recessive trait such as a hitchhiker's thumb to exist, you must receive a recessive allele of the "bendy thumb gene" from BOTH parents. In other words, it takes two recessive alleles to get a hitchhiker's thumb.

How Do You Get A Recessive Trait?

Let's look at an example of how this works. Below is a Punnett Square, which is the accepted method for displaying the probability of having a specific trait.

Let's represent a straight thumb (the dominant allele) with a capital "A", and the hitchhiker's thumb (the recessive allele) with a lowercase "a". The left column represents which allele you received from your mother. The top row represents which allele you received from your father. the cells in the middle represent your genotype, or the genetic makeup you have with respect to the "bendy thumb gene".

Punnett Square

 
Father - Dominant Gene (A)
Father - Recessive Gene (a)
Mother - Dominant Gene (A)
AA
Aa
Mother - Recessive Gene (a)
Aa
aa


In the above example, any outcome that has a capital "A" (the dominant allele), will have a straight thumb. This is the case for the outcome with the "AA" genotype, as well as both cases of the "Aa" genotype. In the latter, the dominant (straight thumb) gene will overpower the recessive one. The only outcome above that will display the hitchhiker's thumb is the "aa" combination of alleles.

In my particular situation, my father displays the hitchhiker's thumb, so his genetic makeup is "aa". I display the hitchhiker's thumb, so mine must also be "aa".

My mother does not display the hitchhiker's thumb. However, in order for me to display it and have the "aa" genotype, I must have inherited a recessive "a" allele from her as well. So, she must have the "Aa" genotype, with the dominant gene masking the recessive one.

Oh no! My thumb is broken! Just kidding!
Oh no! My thumb is broken! Just kidding!

Hitchhiker's Thumb Tricks!

Not many people have seen a hitchhiker's thumb like mine, that can bend backward ninety degrees. So I have a lot of fun playing tricks with it!

I can always scare people (especially kids) by pretending my thumb is broken. I push down on a table and bend it back, acting like I broke it. Guaranteed to freak kids out!

My thumbs are also a great conversation starter. There aren't many people with hitchhiker's thumbs, so most people are surprised at my "ability." After the initial gross-out, it makes for great conversation.

I'm also the grand champion of thumbwrestling! No one can pin me because I can bend my thumb back out of their reach. Ahhh, the perks of a crazy recessive trait!

I've grown to love my thumb weirdness, and am actually a little sad that neither of my children inherited it. It's a bond I will always share with my father and his mother, who both had the same thumbs as I do.

Comments 32 comments

Robie Benve profile image

Robie Benve 4 years ago from Ohio

Wow, I never heard of it before, and I have to admit it makes me quiver a little, because since my thumb does not do that, my mind reads it as uncomfortable and potentially very painful.

very interesting. :)


Nettlemere profile image

Nettlemere 4 years ago from Burnley, Lancashire, UK

I have one too Amy, just like yours in the amount of bend. Hardly seen any others around!


Amy Gillie profile image

Amy Gillie 4 years ago from Indiana Author

Yay, Nettlemere! I'm glad to know another "aa"!!


Amy Gillie profile image

Amy Gillie 4 years ago from Indiana Author

Thanks Robie! It actually doesn't hurt or pull at all. It feels just as comfortable as bending it forward. Now when you see someone with one, you'll know! :-)


Spmccarthy4 profile image

Spmccarthy4 4 years ago from Boston

I have a hitchhiker thumb as well but it bends about twice as far as yours. The one benefit is that i never lose a thumb war haha


Marcy Goodfleisch profile image

Marcy Goodfleisch 4 years ago from Planet Earth

I think I have that trait - but I didn't know that's what it was. I think my mom had it, too - I remember her hands clearly. But I don't recall if my dad had it. Does this have anything to do with a little finger that is almost double-jointed? Both of my little fingers do almost the same thing.

So - are we normal in other respects?


Amy Gillie profile image

Amy Gillie 4 years ago from Indiana Author

Thanks spmccarthy4! I would love to challenge you!


Amy Gillie profile image

Amy Gillie 4 years ago from Indiana Author

Marcy - that's awesome! Now you know all about it. I have only one parent who displayed the trait also. I don't have any double-jointed fingers.

And I would never aspire to call myself "normal"... :-)


Robie Benve profile image

Robie Benve 4 years ago from Ohio

mmmhhh, di I tart to see a correlations between being a writer and having a hh thumb? How interesting!


Nettlemere profile image

Nettlemere 4 years ago from Burnley, Lancashire, UK

I came back to take the poll. Marcy one of my little fingers does that too (my other one got trapped in a dog lead incident some years ago and lost it's double jointedness.)


Michael J Rapp profile image

Michael J Rapp 4 years ago from United States

Yikes! My thumb definitely doesn't do that! Really interesting.


Amy Gillie profile image

Amy Gillie 4 years ago from Indiana Author

Michael - that's the reaction most people have once they notice it! It doesn't hurt though, I promise!


Turtlewoman profile image

Turtlewoman 4 years ago from California

Oh my goodness, that looks painful even though I know it's not. I don't have the bender thumb gene and don't know anyone that does either. Maybe I just never noticed! Thanks for sharing...I was also surprised to get a quick review of a genetics course. :-) Voted up and interesting!


Amy Gillie profile image

Amy Gillie 4 years ago from Indiana Author

Thanks Turtlewoman! I'm so glad you found it interesting!


Craden 3 years ago

My dad me and my sister have the recessive trait too,it was my sister's friend who first noticed it while playing thumb wrestling then we realized can't everybody do it? At first we are kinda freaked out but as time goes by we appreciate this different yet beneficial trait of ours


Job 3 years ago

Oh man I think I am going to throw up...


DAVO 3 years ago

I thought everyone had bendy thumbs till I was 11. To bend ya thumbs so far back is a big benefit i think. I can put most of the force from my arm in to my thumb when pressing down


Brandon 2 years ago

Today someone at my school pointed this out so I came here to research and I'm glad I did. Also all my other fingers do this too.


grmpf 2 years ago

The genetic aspect of this is something that was suggested in the 50s and has since been disputed. It's not that you either have a "Hitchhiker's Thumb" or not; the thumb angle actually varies between people from 0° all the way to 90°.


Alex 2 years ago

I have a hitchhikers thumb and I can play piano just fine.


mik3 2 years ago

I can go past 90 lol if I press down it and it's crazy cus my left thumb goes 90 but right only can get to about 80


Barry 2 years ago

I also have bendy thumb it bend 90 degrees with no pressure I can bend nearly 180 degrees pushing on it. I still freak people out with. I thought it WS normal until secondary school my sister has it as well not as pronounced.


martina mc carthy 23 months ago

My son and partner have it also my brother


Hello 21 months ago

If all your fingers can bend, then you are double jointed ... which is different from having hitchhiker's thumb


Charl Cook 19 months ago

I've got hitchhikers thumb and I just thought I had funny thumbs till today. So received its my genes! I would look at my brother and parents who's thumbs are normal, but now I know my parents with normal thumbs BOTH carry the gene fo me to be effected. I no longer feel a freak but special x


Vikashjin 17 months ago

my thumb is also flexible !! I went far from 90 degrees ! by pressing a table I can almost folded my thumb into two


Zach 14 months ago

I have a flat 90 degree back thumb so a little more than yours (180 degrees of motion) and I honestly had never considered using it for a thumb war. I feel so dumb rn.


Max 14 months ago

I have both of them. I have one hh Thub and one straight one


rohanfelix profile image

rohanfelix 13 months ago from Chennai, India

Great hub! I have hitchhiker's thumb, and I just realized it a while ago. It's affecting my reach as a student of piano, and I find it hard to even reach an octave without pressing the key before the target key. Is there any exercise or treatment that you could suggest for me? Thanks in advance!


IloveHuskys 7 weeks ago

mine does that to!I always thought i had broken it or something as a kid,but now i feel better that i never broke anything!Whenever i thumbs up my friends they always just give a reaction much like this:OMG How do you do that?!That has to hurt!But it really doesnt, im the only one in my class that can do it,all of my friends just lose it when they see it,


Fryderyk Chopin 7 weeks ago

Honestly Hitchhiker's thumb is awful. I can reach a ninth on the piano but could easily reach an 11th with my thumb straight, yet I am not able to straighten it with straining my thumb. Any help or words of wisdom to practice straightening my thumb when playing???


Stephanie Doulgeris 5 weeks ago

i'm not the only one, yay because i thought i was the only one with a weird positioning thumb!!!

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