Last summer professor John T. Manning re-designed his popular 2D:4D digit ratio theory about finger length ratio development in the hand. While he had already mentioned the role of prenatal sex steroids, now the updated theory now focusses on the balance between sexe hormones (androgens) testosterone & oestrogen during the development in the whomb!

Professor Manning presented his revised theory in the PNAS magazine under the title: ‘Resolving the role of prenatal sex steroids in the development of digit ratio‘.

Manning’s new working hypothesis now includes e.g. the following 7 key-elements:

1 – The 2D:4D digit ratio results from the balance between prental androgens testosterone & estrogen;

2 – A high 2D:4D digit ratio results from relatively low testosterone concentrations – OR relatively high estrogen concentrations;

3 – A low 2D:4D digit ratio results from relatively high testosterone concentrations – OR relatively low estrogen concentrations;

4 – The ring finger (= digit 4D) is featured with many more hormone receptors compared to the index finger (- digit 2D), therefore the 2D:4D digit ratio is mostly driven by changes in the length of the ring finger (due to prenatal hormone concentrations);

5 – Studies in human & animals indicate that the link between prenatal androgens and 2D:4D digit ratio is generally stronger for the right hand;

6 – 2D:4D Digit ratio varies with sexe: males generally have longer fourth digits relative to second digits than females;

7 – 2D:4D Digit ratio varies with ethnicity.

A quote from Manning’s article:

“Armed with this list of skeletogenic genes linked to 2D:4D, we can now be more focused in our examination of the links between 2D:4D and the etiology of sexdependent behaviors and diseases of the immune system, cardiovascular disorders, and a number of cancers.”

“Prenatal sex steroids [i.e., prenatal testosterone (PT), prenatal estrogen (PE)] are often implicated in the etiology of behaviors and diseases. They show sex differences (higher concentrations of PT to PE in males), with PT peaking at the end of the first trimester, and cause permanent “organizational” changes in the brain and other organ systems. It has een suggested that relative levels of PT and PE may have differential effects on fertility, speed, strength, aggression, autism, many cancers, and heart disease.”

Full report:
Professor John Manning  revised his 2D:4D finger ratio theory

Most of us have fingerprints, but some people are born with missing fingerprints. Only four families around the world are known to have been born with this disorder - a disease called ‘adermatoglyphia’. Recently dermatologists have found adermatoglyphia in a Swiss family - 9 out of 16 members have no fingerprints - is caused by a smaller version of a gene called SMARCAD1!

Almost every person is born with fingerprints, and everyone’s are unique. In an effort to find the cause of the disease, dermatologist Eli Sprecher sequenced the DNA of 16 members of one family with adermatoglyphia in Switzerland. Seven had normal fingerprints, and the other nine did not. After investigating a number of genes to find evidence of mutation, the researchers came up empty-handed—until a grad student finally found the culprit, a smaller version of a gene called SMARCAD1

The larger SMARCAD1 is expressed throughout the body, but the smaller form acts only on the skin. Sure enough, the nine family members with no fingerprints had mutations in that gene.

Being born without fingerprints doesn’t occur simply because one gene has been turned on or off, Sprecher said. Rather, the mutation causes copies of the SMARCAD1 gene to be unstable.

Full story about missing fingerprints in a Swiss family:
Missing fingerprints in a Swiss family caused by SMARCAD1 gene!

A budding singer from Las Vegas cut her nails for the last time about 18 years ago – resulting in fingernails total nearly 19 feet + 9 inches long! Guinness Records announced a few days ago that Chris Walton will receive a notification in the 2012 edition of the Guinness Book of World Records!

An impression from Chris Walton’s life:

“I never set out to make it into Guinness,” she says. “It just happened. One day I stopped cutting my nails. I liked the way they looked. And they just kept growing.”

An even more impressive Guinness World Record holder for longest nails is Lee Redmond from Salt Lake City. Her fingernails measured a total of 28 feet in 2008, but in 2009 she lost her nails in a car crash.

The story about Chris Walton’s fingernails:
Chris Walton has the longest fingernails!

Wearing your heart on your sleeve is merely an adage, but most people do display their emotions – even if unintentionally – on their faces. Women tend to be better than men at reading other people’s subtle facial cues, especially cues from the eyes. Because of the gender difference in cognitive empathy – the ability to notice and correctly interpret body language – psychobiologistsscientists that study psychology from a biological perspective, or vice versa have hypothesized that testosterone – a sex hormone present in much higher levels in males versus females levels – could play a role in “mind reading” ability, or lack thereof.

A new study in PNASProceedings of the National Academy of Sciences validates this hypothesis by demonstrating that a dose of testosterone can make women lose some of their cognitive empathy. Researchers recruited 16 young women (age 20-25) to participate in their study. The women were given either a testosterone pill or a placebo, and then tested on their ability to assess emotions based on photographs of eyes. The test the women took is called the Adult Eyes Test, and is available for free from the Autism Research Center at the University of Cambridge. Here’s a sample question (formatting is slightly modified):

For the correct answer, click here.

Each woman was tested twice – once with placebo and once with real testosterone (in random order; they didn’t have any idea which was which). 75% of the women performed worse on the “mind reading” test after taking testosterone than after taking a placebo. So to a first approximation, an artificial increase in testosterone levels impaired women’s abilities to interpret facial expressions.

But the results aren’t quite that simple. Some women were less affected by the extra testosterone than others, and the researchers had a hunch that this could relate to their exposure to testosterone in the womb. All fetuses are exposed to testosterone while developing, but to different extents. There is a simple way to qualitatively measure fetal testosterone exposure – this parameter is believed to be correlated to the adult ratio of ring finger length to index finger length (see picture at the top of this post).

Larger ratios of ring finger to index finger lengths correspond to higher fetal testosterone levels. This study showed no difference between the inherent expression-reading ability of women exposed to higher vs. lower doses of testosterone in the womb. However, the women with longer ring fingers (higher fetal testosterone) seemed to be more easily impaired when given a dose of testosterone in pill form.

Thus, this study demonstrated that (1) testosterone administered to women can impair their ability to read facial expressions, and (2) women who experienced more testosterone in the womb are more sensitive to the effects of testosterone administered as adults. Nothing further can be definitively gathered from these results, but they seem to suggest that men’s testosterone levels could be to blame for their increased confusion about what others (especially women!) are thinking/feeling.
 
PS. A brand new study reported by researchers from Florida has recently (sep 2011) presented proof that fingers have hormonal receptors!
 
Via: ICanHasScience

The following finger length study presents a likewise effect:
How lingerie can sharpen the financial mind! 
 

When U.S supercop Bill Bratton and wife Rikki were pictured in The Mail on Sunday last week, her elegantly manicured fingers were lightly – but oh so firmly – resting upon her handsome husband’s torso.

And a little research reveals that in almost every photograph taken of the couple, TV personality Rikki has adopted a similar pose.

Bill is the charismatic policeman credited with reversing America’s crime epidemic – and the fact that Rikki is his fourth wife is perhaps a clue to the significance of her sub-conscious hand signals.

Because body-language expert Judi James says the pose is classically adopted by women everywhere to send a hands-off gesture to any rivals who may be interested in their man.

‘This is a possessive barrier gesture,’ explains James. ‘Although it is a sign of affection, principally it is a signal to other females, who may be potential rivals.

‘Basically, what the woman is communicating to others is, “I’ve got him – hands off.” ’

It’s a tactic that doesn’t work with all men, warns James. So The Mail on Sunday set about finding the stars who use the hands-off hand signal to most effect .  .  . with surprising results.

Via: Emily Hill

A few more ‘hands off, he’s mine’ celebrity-pair examples, including: Angelina Jolie & Brad Pitt, Victoria & David Beckham, J-Lo & Marc Anthony, Katie Holmes & Tom Cruise, Katy Perry & Russell Brand, Emma Thompson & Greg Wise, and Megan Fox & Brian Austin:

- ANGELINA JOLIE & BRAD PITT -

- VICTORIA & DAVID BECKHAM -

- J-LO & MARC ANTHONY -

- KATIE HOLMES & TOM CRUISE -

- KATY PERRY & RUSSELL BRAND -

- EMMA THOMPSON & GREG WISE -

- MEGAN FOX & BRIAN AUSTIN -

A few quotes from respected philosophers describing the philosophical importance of hands:

Aristotle (384BC - 322BC)

“… (the hand) is the organ of the organs, the active agent of the passive powers”

Sir Charles Bell (1774-1842).

“The hand is essentially the organ of the mind, the medium of its expression, and the Instrument whereby its promptings are carried into execution”

Carl Gustav Jung (1875-1961).

Carl Gust Jung, the Swiss psychiatrist said:

“Chirology [hand reading] is an art which dates back to very ancient times. The ancient physician never hesitated to make use of such
auxiliary systems as chiromancy and astrology for diagnostic and prognostic purposes as is shown, for instance, by the book of Dr. Goclenius who lived at the end of the sixteenth century. … The totality-conception of modern biology which is based on the evidence of a host of observations and research does not exclude the possibility that hands, whose shape and functioning are so intimately connected with the psyche, might provide revealing and therefore, interpretable expressions of psychical peculiarity, that is, of the human character. …”

Today, the hand can be used to study the significance of hand signs in the perspective of quite a few syndromes, diseases, and psychiatric disorders. You can check out many more details about dozens of hand signs via the sources below:

• 34 Hand signs in Diabetes Mellitus (type 1 & 2)

• 29 Hand signs in Down syndrome (trisomy 21)

• 30 Hands signs in Fragile-X syndrome

• 5 Hand signs in Marfan syndrome

• 24 Hand signs in Psoriasis

• 28 Hand signs in Rheumatoid Arthritis

• 37 Hand signs in Schizophrenia 

More hand art is available at:
http://www.handresearch.com/hand/Evolutie/kunstEngels.htm

A few impressions of Thomas Hooper’s hand art tattoo mandalas:

A mole has (only) 5 digits + a large sickle shaped sesamoid bone.

Vertebrates usually have five fingers on each hand, but in some specifies – including the Great Panda & the Mole – the hand ‘appears’ to be featured with an extra thumb (polydactly). Earlier this week paleontologists from the University of Zurich have uncovered a new theory about the underlying biological causes that are responsible for the mole’s extra thumb.

The researchers see a connection between the species-specific formation of the extra thumb in the mole and the peculiar “male” genital apparatus of female moles. In many mole species, the females have masculinized genitals and so-called “ovotestes,” i.e. gonads with testicular and ovary tissue instead of normal ovaries. Androgenic steroids are known to influence bone growth, transformation and changes, as well as the transformation of tendons in joints. A high level of maternal testosterone is also thought to be one of the causes of polydactyly in humans.

ABOUT SESAMOID BONES & EXTRA THUMBS! 

Anatomically, what ‘appears’ to be extra thumb that is seen in the Mole and the Giant Panda can be described as the result of excessive growth of the so-called sesamoid bones which are typically found in all vertebrates at the end of the thumb metacarpal.

NOTICE: Sesamoid bones are found in locations where a tendon passes over a joint.

In the human hand sesamoid bones are rather small and they act to protect the tendon and to increase its mechanical effect – so they play a key role in the multi-functionality of the human hand, see the picture below.

- Sesamoid bones in the human hand -

However, in some other vertebrate species sesamoid bones have a more explicite function for it’s owner.

E.g. in the mole’s paw the extra thumb is shaped by a sesamoid bone manifesting as a sickle shape which gives the mole a bigger surface for digging.

And in the Giant Panda’s paw the extra thumb is actually shaped by a radial sesamoid larger than the same bone in counterparts such as bears. It is primarily a bony support for the pad above it, allowing the panda’s other digits to grasp bamboo while eating it. 

The Giant Panda has 5 digits + a large sesamoid bone.

 
NOT A REAL FINGER!

These considerations implicate that Moles and Giant Pandas do not really have an extra finger. This is confirmed by the fact that their ‘appearance’ of an extra finger is not featured with other typical characteristics seen in the other fingers – e.g. a nail (claw) & phalanges are missing, and embryology studies have revealed that the extraordinary sesamoid bone in both the Mole and the Panda starts developming at a much later stage compared to the 5 digits that are typically seen in every vertebrate!

MORE ABOUT THE HANDS IN VERTEBRATES:
• The mystery of the five fingers

Finger length ratio predicts penis length!

JULY 4, 2011 – Finally… researchers in Korea think that they found the long awaited proof: finger length can predict penis length! Korean researchers at the In Ho Choi of Gacheon University Gil Hospital, have presented results in a sample of urological patients which indicate that in men with a low ’2D:4D finger ratio‘ more often is featured with a long phallus (compared to men with a high ‘digit ratio’).

The researchers from Korea found that the ratio between the pointer finger & ring figner (2nd and 4th digits) on men’s right hand correlate to the length of his flaccid and stretched phallus (not errected). A lower index-to-ring finger length ratio indicates a longer (stretched) penis.

NOTICE: The table below is taken from the scientific article; it e.g. illustrates that likewise results were found for body length and penis length – for the ‘flaccid condition’ the result for body height were slightly higher than for the 2D:4D digit ratio, but in the ‘stretched condition’ finger length ratio was a better predictor for penis length!

The key to this relationship between penis size & finger length likely lies in the womb, a team member added:

“During the fetal period, high concentrations of testosterone lead to high testicular activity, resulting in a lower digit ratio, in the present study, patients with a lower digit ratio tended to have a longer stretched penile length.”

The researchers also added that the length of the stretched and flaccid penis does show “a strong correlation” with an erect penile length.

The Korean report was published on july 4 in the Asian Journal of Andrology, and the scientific article is available at Nature.com.

NO SURPRIZING RESULTS!

Finger names in Korean language.

Actually, the Korean results are not surprizing at all. Because British professor John Manning had already pointed out in his second book ‘The Finger Book‘ (2008) that a study in the Naval and Veteran’s Hospital of Athens (Greece, 2002) had pointed out that the length of the index finger correlates with the length, glans & volume of the penis.

Manning commented (in ‘The Finger Book’):

“Spyropoulos and his collegues did not measure the remaining fingers, so we cannot be sure of their relationship to penis length. My guess is that they would have found the ring finger the strongest predictor, and that long ring fingers in relation to index fingers would be associated with longer penises.”

So, the 2011 Korean study shows ‘finger professor’ John Manning was right… again!

MORE ABOUT THE SCIENCE OF FINGERS: 
48 Reports about the 2D:4D finger length ratio!

The X-Finger is developed by Dan Didrick (Didrick Medical Inc.) and it has been presented as the world’s first active-function artificial finger assembly designed specifically for partial finger amputees. This finger device provides users to regain complete control of the flexion and extension movements with an artificial finger in a self-contained device.  The X-Finger wass designed to bend a silicone finger sheath in a very realistic manner.

Dan Didrick was motivated in part by a desire to help a hearing-impaired person regain sign language ability after losing fingers. He whittled his first concept prototype out of pine wood.