‘The Finger Book’ – by John Manning: a book about finger length!

The Finger Book - author: John T. Manning

Book Review: The Finger Book – author: Prof. John T. Manning, psychologist, University of Liverpool Publisher (Fabe and Faber, 2008) comment: “This book employs finger ratio to examine a group of questions about human behaviour, from sexuality, to musical ability, to predisposition to disease.”

The publisher writes about John Manning’s book The Finger Book: “This book is about a simple measurement of the human hand: the ‘finger ratio’. What could fingers & sex possibly have in common? What does the shape of a child’s fingers reveal about future music talent? Why should professional footballers have longer ring fingers than other men? This book is about a simple measurment of the human hand. You may not have noticed that men tend to have longer ring fingers relative to their index fingers, and it turns out this tiny sex difference is highly revealing. John Manning, ‘a pioneer in this field’ (New Scientist) uses it to examine a dizzying group of questions about human behaviour, from sexuality, to music ability, to predisposition to disease. Controversial, but untainglingly clear and balanced, John Manning presents his cutting-edge research for the reader to consider. The finger length ratio (2D:4D) appears to tell us what happens to babies in the whomb, indicating the amount of testosterone and oestrogen to which each foetus is exposed. This early evens has, it seems, profound consequences in each of us. Provocative, arresting and direct, The Finger Book makes accessible a whole new area of evolutionary science, and poses many fruitful questions about what makes us as we are.”

Book review by Michael E. Mills: ‘Digit ratio: A Pointer to Fertility, Behavior and Health’!

Digit Ratio: A Pointer to Fertility, Behavior and Health

Book Review: Digit Ratio: A Pointer to Fertility, Behavior and Health – author: John T. Manning Publisher: Rutgers University Press 2002 Review by Michael Mills, Psychology Department, Los Angeles.

Michael Mills writes about John Manning’s book Digit Ratio: “Take a look at your right-hand. Which of your fingers is longer: your ring finger, or your index finger? Surprisingly, a passing stranger who noticed a difference in length between these two fingers (and who had handy a copy of John Manning’s book Digit Ratio: A Pointer to Fertility, Behavior and Health) might infer some very personal characteristics about you. With no more data than that gleaned from a passing glance at your hands, a stranger might infer whether you are likely to have homosexual inclinations, are highly fertile, may eventually suffer from a heart attack or breast cancer, have musical aptitude or sporting prowess, and a surprisingly long list of other characteristics. …Females typically have index and ring fingers of about the same length. The ratio of index finger length to ring finger length is called the “2D:4D digit ratio,” or more simply, the “digit ratio.” Manning reports that, for males, the index finger is generally about 96 percent of the length of the ring finger, which gives an average digit ratio for males of .96. …Manning devotes separate chapters to explore the relationship between digit ratio and a variety of characteristics, including assertiveness and attractiveness (chapter 3), reproductive success (chapter 4), hand preference, verbal fluency, autism, and depression (chapter 5), health and disease (chapter 6), homosexuality (chapter 7), musical aptitude (chapter 8 ) and sports aptitude (chapter 9). A brief summary Manning’s findings (some of which he notes are quite preliminary) is presented in the table below.”

	Low 2D:4D ratio	High 2D:4D ratio
Males	* More fertile * Higher lifetime reproductive success * More aggressive and assertive * Greater proclivity toward homosexuality/bisexuality * Higher musical and sports aptitude * Lower SES (?)	* Higher risk of early heart disease
Females	* Greater proclivity toward homosexuality/bisexuality * More aggressive and assertive	* More fertile * Higher lifetime reproductive success * Higher risk of breast cancer

Digit ratio: finger length research in primates!

Emma Nelson studies

‘Digit ratio’ in non-human primates: ‘Digit ratio’ research is not limited to the human hand. Emma Nelson from Department of Archaeology, University of Liverpool is one of the key-researchers who studies ‘digit ratio’ in the hands of primates. The major focuss in Emma Nelson’s ”digit ratio’ research in primates is:

“Using digit ratios (2D:4D) to investigate social systems in anthropoids; implications for the study of the evolution of hominin sociality.”. Variation in non-human primate 2D:4D is currently unknown. One of the aims of this project is to map differences in mean 2D:4D within and between non-human primates species.

7 Milestones in the history of ‘digit ratio’!

A short history of major the developments in the concept of ‘digit ratio’:

In 1888 antropologist and biologist Dr. Frank Baker noticed that the index finger is usually short than the ring finger:

More than a hundred years ago, a very entertaining paper concerning various customs and superstitions associated with the hand – titled: ‘Anthropological Notes on the Human Hand‘ (1888) – was presented to the Antropological Society of Washington by Frank Baker, Professor of Anatomy at the University of Georgetown. Following some fascinating tales, and a debunking of palmistry, he concluded by discussing the comparative lengths of the digits, and noted that the second (index) finger is usually shorter than the fourth (ring) finger.

In 1930 antropologist Ruggles George noticed a sex difference in the index finger and the ring finger:

Some years later R. George described in a paper – titled: Human Finger types (1930) – a sex difference in the distribution of finger length ratios in that males are more likely to show the 2 < 4 pattern (i.e. a longer ring finger relative to the index finger), while females are more likely to show the opposite pattern (2 > 4).

In 1952 antropologist V.R. Phelps discovered that finger length is stable throughout life:

Two decades later the sex difference findings reported by George (1930) were confirmed in the work of V.R. Phelps – titled: Relative index finger length as a sex-influenced trait in man (1952) – noting that such differences were observed in foetuses, and then appeared to be stable throughout life.

Psychologist Glenn Wilson

* In 1983 Psychologist Glenn Wilson introduced the word ‘digit ratio’: Dr Glenn Wilson of King’s College, London published a study – titled: ‘Finger length as an index of assertiveness in women‘ – which introduced the 2D/4D ‘digit ratio’ as a marker of exposure to prenatal testosterone + examining the correlation between assertiveness in women and their digit ratio. This was the first study to examine the correlation between digit ratio and a psychological trait within members of the same sex.

Psychologist John T. Manning

* In 1998 Psychologist John T. Manning presented a link between ‘digit ratio’ and testosterone + sperm counts: This link was described by Manning in a study – titled: ‘The ratio of 2nd to 4th digit length: a predictor of sperm numbers and concentrations of testosterone‘.

Digit Ratio - the book

* In 2002 Psychologist John T. Manning presented the book ‘Digit ratio’: Psychologist John T. Manning presented his first book about the 2D:4D ratio – titled: ‘Digit ratio: A Pointer to Fertility, Behavior and Health‘. In this book Manning presents a first overview of the digit ratio research which has been presented uptill the year 2002.

The finger book

* In 2008 Psychologist John T. Manning presented the book ‘The finger book’: Psychologist John T. Manning presented his first book about the 2D:4D ratio – titled: ‘The finger book‘. Quote from New Scientist: “According to evolutionary psychologist John Manning, who has spent years researching the secrets they betray, your digits reveal all sorts of things, from your sexuality to whether you are socially disadvantaged or likely to suffer a heart attack. They even, as the legend goes, give away the size of a man’s penis.”

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

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):

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!

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:

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.