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Hitchhiker's thumb[edit]

The reading says that no Hitchhiker's thumb has no ill-effect on the thumb's function. I don't believe that. I have Hitchhiker's thumb, and often times, when I grasp something, I bend my thumb way back. Us441 (talk) 15:25, 4 February 2010 (UTC)

In fact this entire section appears to be bullshit... but I'm not much a wikipedia-er so I'm not going to edit the article. Apparently this is a common genetic myth: -- (talk) 04:09, 3 June 2011 (UTC)

Yeah, the only evidence for it being a recessive trait is this article from 1953. I'm going to edit the section to make it a bit more balanced. Nickopops (talk) 12:12, 7 November 2012 (UTC)

"The thumb contrasts with each of the (other) four by being the only finger opposable"[edit]

Opposable redirects to this article. The "Opposable thumbs" section states that "An animal species is said to have opposable thumbs if the thumb is capable of bending in such a way that it can touch all the other digits on the hand." Farther down in the article is the statement that "The thumb contrasts with each of the (other) four by being the only finger opposable". If opposability refers to a digit with the ability to touch all the other digits on that hand, then a quick personal test demonstrates to me that all human fingers are opposable (I know that different people have different ranges of motion, so this may not be 100% true, but I suspect it is widespread). I think either the definition of opposability needs to be clarified, or this statement needs to be removed. cmadler (talk) 12:16, 6 April 2010 (UTC)

This article is indeed a bad mess. To my knowledge, 'true' opposability refers to the ability to bring the distal pads of two fingers together, and most humans can bring the thumb into opposition to all other fingers. Chimpanzees, on the other hand, can bring thumb and index finger into contact, but are not able to oppose their distal pads. The best definition I've found is this:
Napier and Napier define opposition as: "A movement by which the pulp surface of the thumb is placed squarely in contact with - or diametrically opposite to - the terminal pads of one or all of the remaining digits". While an opposable thumb is one of the hallmarks of humans, it is not unique to the species. What is unique to Homo sapiens sapiens is the broad area of the contact achieved between the compressible pulps of the index finger and thumb. Not all primates are capable of opposing their thumbs. The necessary movement for true opposability is the rotation of the about its own long axis. Without this rotation the movement of the thumb towards the palm is a form of pseudo-opposability where pulp-to-pulp contact of the thumb and digits is not possible.
"Primates FAQ: Do any primates have opposable thumbs?". 
The article really needs some clean-up. --Fama Clamosa (talk) 13:01, 6 April 2010 (UTC)

But since we say that the birds' feet- the 1st digit- is opposable, why should we argue on that of primates? Sky6t (talk) 00:56, 9 August 2011 (UTC)

The palmar aspect of the thumb: what is it?[edit]

User:Fama Clamosa has added the following para in the section "As one of five digits, and as companion to four fingers":

  • Opposition and apposition — two movements unique to the thumb — are not synonyms. Opposition is when the palmar aspect of the thumb is brought into contact with the fifth digit (little finger); apposition is when the thumb is approximated to another digit not using the palmar aspect. [2]

Can this be somewhat clarified? I take it when the non-palmar aspect of the thumb is offered up to the any of the others fingers, it is tucked under the finger(s)singularly or similar to a clenched fist but the thumb tucked inside all the fingers? Is that then apposition you mentioned? Dieter Simon (talk) 01:58, 19 November 2010 (UTC)

Yes and no, I guess. The reference is somewhat unclear in the second line below:[1]
Thumb: approximation of the palmar aspect of the thumb and fifth digit
Thumb: approximation between the thumb and other digit not using the palmar aspect
I suppose they mean the palmar aspect of any digit.
Furthermore, these two words are used differently elsewhere. Often a distinction is made between "[incomplete] opposability" and [true] opposability (i.e. human opposability). For example, Napier and Napier defines it:
"A movement by which the pulp surface of the thumb is placed squarely in contact with - or diametrically opposite to - the terminal pads of one or all of the remaining digits". While an opposable thumb is one of the hallmarks of humans, it is not unique to the species. What is unique to Homo sapiens sapiens is the broad area of the contact achieved between the compressible pulps of the index finger and thumb. Not all primates are capable of opposing their thumbs.[2]
So according to the first reference, opposition always involves the little finger and the palmar aspect of the thumb. Which makes sense since these two digits have two muscles named for this movement (opponens pollicis and opponens digiti minimi). As far as I can tell, a clenched fist is definitely neither apposition or opposition but holding something with the hand in a similar position is. Most definitions would agree the palmar aspect of the thumb must be involved for the opposition to be "true"; other primates can have the tip of their thumbs touch some of the other digits but are not able to use this for a firm grip, but this fact is often ignored by [human] anatomists. --Fama Clamosa (talk) 10:31, 19 November 2010 (UTC)
I guess all this was to say I agree the article needs clarification. --Fama Clamosa (talk) 10:35, 19 November 2010 (UTC)
I've expanded and modified this part of the article. Hopefully things are more clear/detailed now. --Fama Clamosa (talk) 15:21, 20 November 2010 (UTC)
Maybe the entire paragraph on opposition/apposition should be moved to a separate section? Looking at the article and redirects such as opposable and opposable thumb, there is perhaps even enough information for a new separate article on opposability? --Fama Clamosa (talk) 20:06, 20 November 2010 (UTC)
Thank you, you have added a lot to this article and it is very much appreciated. You certainly elucidate things, especially since you are citing good sources in your explanations. The only problem is, moving the paragraph of the opposition/apposition section needs to be well linked to this article, so that it still appears as a part of the subject "thumb" over all. What do you think, could that be done? Dieter Simon (talk) 00:36, 21 November 2010 (UTC)
Thanks. A lot of articles mention "opposable" (but only a few articles actually link to it) and, for example, dinosaurs' digits can be opposable [first digits] without being "thumbs" (human definition). So a separate article makes sense. On the other hand, as you said, the thumb article can hardly be written without describing opposability, and I'm not sure Opposability can be written without a lengthy description of the thumb. I guess my preferred solution is (1) a separate section on opposability in this article and (2) redirects directly to that section. --Fama Clamosa (talk) 10:50, 21 November 2010 (UTC)
I made opposition/apposition a separate section and redirected a number of pages to that section. If the section grows large enough, it can now easily be exported to a separate article. --Fama Clamosa (talk) 11:24, 21 November 2010 (UTC)
Sounds perfectly reasonable to me, many thanks. Dieter Simon (talk) 19:00, 21 November 2010 (UTC)

"The thumb contrasts with each of the other four by being the only finger that..."[edit]

The subject sentence, found within the Definition section, implies that the thumb is a finger. Apparently, the thumb is not a finger (according to a few paragraphs prior). Perhaps the word "finger" should be changed to "digit"? (talk) 04:21, 20 May 2011 (UTC)

Other animals with opposable digits[edit]

No mention there of squirrels, though they do have thumbs, according to But I do not know if theirs are opposable or not --Julien Demade (talk) 19:09, 23 March 2012 (UTC)

Redundant references[edit]

I removed the following sentence from the article because it is sort of a no-brainer. It would be useful if it described a specific property in primate thumbs, but it adds virtually nothing to the article. The link is a 404 but the same source can be found here: [3]. Primate dexterity is better described elsewhere in the article, so we can do without this. --Fama Clamosa (talk) 11:15, 12 August 2012 (UTC)

The thumb, in conjunction with the other fingers, makes human hands and those of other species with similar hands some of the most dexterous in the world.
Chaisson, Eric J. (2007). "Cosmic Evolution — Epoch 6 - Biological Evolution". Tufts University. Retrieved April 26, 2007. {{dead link}}

I also removed the following not obviously helpful statements from the same section. --Fama Clamosa (talk) 12:20, 12 August 2012 (UTC)

The opposable thumb has helped the human species develop more accurate fine motor skills. It is also thought to have directly led to the development of tools, not just in humans or their evolutionary ancestors, but other primates as well. The opposable thumb ensured that important human functions such as writing were possible.
"Lesson Plans — Chimps, Humans, Thumbs, and Tools". National Geographic. 2006. Retrieved April 26, 2007. 
Damonte, Kathleen (February 2004). "Thumbs Are Handy Digits". National Science Teachers Association: Science & Children: The Elementary Science Classroom. Retrieved April 26, 2007. 

"First" finger/digit[edit]

Is it accurate and objective to call the thumb the "first" finger/digit on the hand? How do we define what is first? My thumb can be first on my right had if I am looking at the back and counting from the left to right, is this really what it means or is there some more scientific meaning behind the word "first" used here. If so, shouldn't it be better defined? (talk) 03:52, 18 December 2013 (UTC)

Opposable thumb[edit]

It redirects here, but this article does a poor job at explaining this concept. Also, can somebody stub Opposable big toe? --Piotr Konieczny aka Prokonsul Piotrus| reply here 01:40, 13 September 2012 (UTC)

Evolution of The Human Thumb[edit]

First, this article could be improved by taking a more in depth look at anatomical differences between modern humans and their distant primate relatives. Modern humans are unique in the musculature of their forearm and hand. Yet, they remain autapomorphic, meaning each muscle is found in one or more non-human primates. The extensor pollicis brevis and flexor pollicis longus allow modern humans to have great manipulative skills and strong flexion in the thumb.

Secondly, this article has a very clear depiction that bipedalism evolved after and maybe a result of “busy hands.” However, there are several studies that support the exact opposite. That walking allowed hands to become free for other activities and as a result hand movements became more complex. The complex movements then in turn made stone technology possible.

Lastly, the article could have expanded on the evolutionary history of the thumb. [1]

Chorba.12 (talk) 21:55, 30 September 2014 (UTC)chorba.12Chorba.12 (talk) 21:55, 30 September 2014 (UTC)

  1. ^ Diogo, R., Richmond, B. G., & Wood, B. (January 01, 2012). Evolution and homologies of primate and modern human hand and forearm muscles, with notes on thumb movements and tool use. Journal of Human Evolution, 63, 1, 64-78.