How the ‘digital formula’ became the ‘digit ratio’ formula’!

September 27, 2008

Take a look at your feet…

What do you see? Most of us will see 5 toes … and very likely your inner toe will be the longest, the largest, AND the biggest! As a matter of fact, this a typical characteristic of the human foot!

Now, let’s take a look at the feet of primates… (see the picture below):

The primate foot and the human foot.

Do you see the difference? The foot of these primates show quite a different picture: for, the inner toe is always the lowest set toe! This is a typical characteristic of the primate foot. And often the length of the inner toe does not pass the length of the other toes. 

Another rather remarkable aspect is the fact that the ‘big toe’ of primates (the inner toe) shows quite some similarities with the thumb of our hands.

These typical characteristics in human and primate foot were already described in 1920 in the work PRINCIPLES OF ANATOMY presented by Frederic Wood Jones. Wood Jones described these characteristics through the concept: DIGITAL FORMULA.

The typical ‘digital formula’ for the human foot is: 1>2>3>4>5 – in the typical human foot the inner toe (toe 1) is usually the longest, and the little toe (toe 5) is usually the shortest.

However, the typical primate foot is characterised by the so-called ‘simian digital formula’: 3>4>2>5>1 – in the typical primate foot the middel toe (toe 3) is usually the longest, and the ‘inner toe’ (toe 1) the shortest!

Notice: Jones’ describes on page 30:

 “… the digital forumula*, and it must be remembered that such a formula does not express the relative length of the digits, but the relative projection of the tip of the digits from the extremity of the limb”.

The ‘human digit formula’ for our hands…

Interestingly, the typical ‘digital formula’ for the primate foot resembles the typical ‘simian digital formula’ for the primates hand: 3>4>2>5>1 – you see the confirmation in the picture below!

How to measure digit ratio?

As a matter of fact, the ‘digital formula’ of the human hand often resembles the typical ‘simian digital formula’: 3>4>2>5>1 – especially in the hand of human males! But also the hands of human females can often be characterized by the ‘simian digital formula’, however more often the hands of women can be described with the ‘human digital formula’: 3>2>4>5>1.

The difference is that in human males the ring finger is more often larger than the index finger (or: pointer finger) – which resembles the  ‘simian digital formula’! In human females more often the index finger is longer than the ring finger – which resembles the ‘human digital formula’! These principles are visible in the picture below:

Digit ratio in the male and the female hand

The ‘digit ratio’ formula!

However, both in human males and females the length difference between the index finger (digit 2) and the ring finger (digit 4) is often very small. And therefore the ‘ratio’ between the length of those fingers is often close to ‘one’ (1.00) – when both fingers have the same length, the ‘ratio’ between the 2 fingers is exactly ‘1.00’.

Because of this situation scientists around the world are using the concept ‘digit ratio’ to study the relative length difference between the index finger (digit 2 = 2D), and the ring finger (digit 4 = 4D), which results in the formula: ‘digit ratio’ = 2D:4D.*

* One should notice here that the concept of Wood Jones ‘digital formula’ is related to “… projection of the tip of the digits from the extremity of the limb” -see the 3th picture in this blog post). However, the ‘digit ratio’ is related to the absolute length difference between the index finger and the ring finger – see the picture below.

How to measure digit ratio?
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11 Responses to “How the ‘digital formula’ became the ‘digit ratio’ formula’!”

  1. amar Says:

    hi,
    is feminish didgit ratio say 1.00 realy linked to transexualism.if this has to be true then polish or danish men would have been all trans? whats your take at this?

    • fingerlengthdigitratio Says:

      Hello Amar,

      No, you’ll have to put everything in the perspective of the average digit ratio in the Danish population… and whether the individual is a male or female of course.

      Is this enough for you to understand this research?

      Anyway, thanks for asking! 🙂

  2. dr okamkpa chikezie Says:

    is there any other method one can use to collect data apart from the photocopy method .I need your assistance as wish to establish a digit ratio of a particular ethnic group in africa.

    • fingerlengthdigitratio Says:

      Hello dr Okamkpa Chikezie,

      Yes, there are other methods.

      You can for example measure the finger length directly from the hand with a measurement tool like this:

      Have I answered your question?

      Greetings from The Netherlands!

  3. okamkpa chike Says:

    please what is the exert anatomical land mark for measuring the digits.

    • fingerlengthdigitratio Says:

      Hello Okamkpa,

      The anatomic landmark for measuring the digit length in John Manning’s 2D:4D are the creases where the fingers connect with the palm – which is only found in the inner hand (measuring the length of hand bones result in completely different measurements, featured with a much lower ratio).

      Have I answered your question?

      🙂

  4. Tft Says:

    Hi all,
    My Digit ratio is around 1 using a photocopy but I’ve seen the X-rays and I’m pretty sure that using a X-ray and measuring the bones my digit ratio would be around 0.96-0.97.

    Which is the best way to measure it?

    I’m a male from the group of Spain, Poland and England.

    • fingerlengthdigitratio Says:

      Hello Tft,

      Thank you for your specified question!

      The issue of the ‘digit ratio’ as measured via the points where the fingers involved connect with the palm, should not be ‘mixed’ with X-rays measurements (not impressions from the back of the hand, etc.).

      By the way, there are a few studies where the difference between the various methods of measurement where compared – and X-rays always result in much lower values (typically below 0.95 and even close to 0.90 instead of the normal values).

      And yes, males from Spain, Poland, and England typically have a digit ratio close to 1.0 (usually a bit smaller) – so your digit ratio of 1.00 is not unusual for a male at all… though it is not ‘typical’ for a male either.

      Unfortunately you didn’t describe your nationality… 🙂 (otherwise maybe I would have been able to share a few more thoughts)

      Kind regards from The Netherlands,

      Martijn.

  5. Scott Says:

    What is the typical male data spread within humans for the digital ratio?

    Is there data for this?

    For example my ring finger was 64mm and my index finger was 58mm resulting in a 0.906 ratio.

    • fingerlengthdigitratio Says:

      Hi Scott,

      Thank you for sharing your measurements – 0.906 is for sure a ‘low’ digit ratio (regardless of your ethnicity).

      The trouble is that the ‘digit ratio’ varies very significantly among ethnic populations. In his second book ‘The Finger Book’, Prof. John Manning described that:
      – the average for Zulus, Finish & Jamaicans varies from 0.93 to 0.95
      – the average for Hungarians, Hungarian Gypsees, Germans & Indian varies from 0.96 to 0.97
      – and the average for Spanish, Polish and English people varies from 0.98 to 1.00.

      So, for example: if you’re from Spain, Poland or England then your ‘digit ratio’ is actually very low.

      I hope this makes sense now?
      Anyway, thank you for your question!

      Greetings from The Netherlands,

      Martijn.

  6. Mr WordPress Says:

    Hi, this is a comment.
    To delete a comment, just log in, and view the posts’ comments, there you will have the option to edit or delete them.

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