July 16, 2011
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.
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
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!
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!