Hand shape gives a clue about Genes, Chromosomes & DNA!

APRIL 22, 2013

Hand shape gives a clue about Genes, Chromosomes & DNA!

Hand shape is often presumed to represent the domain of the palmist; however, the truth is that our hand shape actually represents a clue about our genes, chromosomes and DNA!

To make a long story short: human hand shape & finger length proportions typically display a combination of unique characteristics in the primate family. And genetic & chromosomal characteristics play a key-role in the variations between human individuals!

A precise assessment of hand shape requires a measurement of three aspects of the hand, including: (1) finger length [via the longest digit], (2) palm breadth, and (3) palm length.

Structure of a DNA polymerase for the hand: palm, finger, thumb & pad.

Structure of a DNA polymerase for the hand, including: palm, fingers & thumb.

The two pictures below present a quick visual summary of how what distinguishes human hand shape from the proportions seen in other primate species.

The 3 ratios between these three aspects then represent the major key-aspects of the hand shape; where the most interesting results are found when the finger length to palm breadth ratio [= fl/pb] is plotted against the summary of finger length to palm length [fl/pl] + palm breadth to palm length [pb/pl].

- PRIMATE HANDS IN EVOLUTION -

The primate hands in evolution grouped by primate sub-family (drawn hands inside the
picture above origin from A. H. Schultz, The Life of Primates, Universe Books, 1969).

- HAND SHAPE CORRELATES WITH DNA (= GENETIC DISTANCE) -

The plot above describes how human hand shape (upper left quadrant) varies from hand shape in the great apes (lower left quadrant), old world monkeys (lower right quadrant), new world monkeys + prosimians (upper rigth quadrant); more details in table below.

NOTICE: Percentages show genetic distance (in terms of DNA) for primate species compared to humans; especially inside each primate sub-family the percentages correlate with the distance inside the plot to the coordinates of human hand shape.

1D = Thumb | 2D = Index finger | 3D = Middle finger | 4D = Ring finger | 5D = Pinky finger

PRIMATE SPECIES	Genetic distance to humans	Finger length vs. Palm breadth ratio	Finger length vs. Palm length ratio	Palm breadth vs. Palm length ratio	Digit Formula	2D:4D ratio
_Human apes:
Humans	-	0.980	0.764	0.781	3D>4D>2D>1D>5D	0.96
_Non-human apes:
Bonobos	0.017%	1.05	0.71	0.67	3D>4D>2D>5D>1D	0.94
Chimpanzees	0.016%	1.128	0.688	0.610	3D>4D>2D>5D>1D	0.91
Gorillas	0.019%	0.662	0.549	0.879	3D>4D>2D>5D>1D	0.89
Orangutans	0.031%	1.116	0.571	0.512	3D>4D>2D>5D>1D	0.89
Gibbons	0.042%	1.909	0.940	0.493	3D>2D>4D>5D>1D	1.03
_Old World Monkeys:
Macaques	0.061%	1.174	0.740	0.630	3D>4D>2D>5D>1D	0.85
Baboons	0.066%	0.846	0.579	0.684	3D>4D>2D>5D>1D	0.86
Guenon monkeys	0.063%	1.163	0.641	0.551	3D>4D>2D>5D>1D	0.86
Longnose monkeys	0.072%	1.500	0.761	0.507	3D>4D>2D>5D>1D	0.83
Surili monkeys	0.071%	1.184	0.577	0.487	3D>4D>2D>5D>1D	0.80
Colobus monkeys	0.072%	1.459	0.730	0.514	3D>4D>2D>5D>1D	0.65
_New World Monkeys:
Capuchin monkeys	0.123%	1.140	0.814	0.714	3D>2D>4D>5D>1D	1.09
Squirrel monkeys	?	1.140	0.864	0.758	3D>4D>2D>5D>1D	0.93
Tamarin monkeys	?	1.238	0.722	0.583	3D>4D>2D>5D>1D	0.94
Night monkeys	?	1,146	0.786	0.686	3D>4D>2D>5D>1D	0.84
Spider monkeys	?	1.325	0.693	0.533	3D>4D>2D>5D>1D	0.83
_Prosimians:
Tarsiers	24.8%	2.080	1.531	0.745	3D>2D>4D>5D>1D	1.02
_Non tarsier prosimians:
Lemurs	22.1%	1.444	0.813	0.563	4D>3D>5D>2D>1D	0.74
Aye-ayes	?	2.111	1.583	0.750	4D>3D>5D>2D>1D	0.63
Bush babies	28.1%	1.500	1.154	0.769	4D>3D>5D>2D>1D	0.66
Lorises	?	1.500	1,071	0.714	4D>3D>5D>1D>2D	0.60
Slow lorises	?	1.300	0.813	0.625	4D>3D>5D>1D>2D	0.45
Potos	?	1.300	0.765	0.588	4D>3D>5D>1D>2D	0.20

The data in the table above shows how next to hand shape also finger length (digit) distribution provide a sign of evolution. The digit formula shows how the role of the pinky finger (5D) becomes less prominent while going up in primate evolution tree: in humans the pinky finger is usually the smallest of all 5 digits, while in prosimians the pinky is usually longer than the two fingers on the opposite side of the hand: the thumb and the index finger. And the reversed tendency is seen in the middle finger (3D), which is usually the longest digit of all... except in the prosimian hand (non-tarsier) - where the ring finger is the longest digit.

Interestingly, a likewise tendency is seen in respective the ring finger (4D) and the index finger (2D) - where the 2D:4D digit ratio between these fingers tends to become higher while going up in the primate evolution tree.

This likely implicates that the pinky (5D) & ring finger (4D)can be recognized to represent the more 'primitive' fingers, while the thumb (1D), index- (2D) and middle finger (3D) can be recognized to represent the more 'evolved' fingers (one can also speak of the more 'specialized' or more 'complex' fingers). The Youtube-video below presents a visualization of the evolution of hand shape and finger length distribution.

- HAND SHAPE CORRELATES WITH GENETICS & CHROMOSOMAL CHARACTERISTICS -

But hand shape signals more than just the genetic distance (DNA) in the evolutionary perspective. Because hand shape provides also a clue regarding chromosomal- and genetic disorders, such as: Down syndrome, Fragile-X syndrome, achondroplasia & Marfan syndrome. The picture below presents an overview of some of the most common chromosomal- and gentic disorders.

Plot describes how human hand shape correlates with genetic & chromosomal characteristics for males, females + various genetic sub-populations (such as: Down syndrome, Fragile-X syndrome, Marfan syndrome & achondroplasia); more details in table below.

HUMAN SUB-POPULATION	Genetic peculiarity	Finger length vs. Palm breadth ratio	Finger length vs. Palm length ratio	Palm breadth vs. Palm length ratio	Digit Formula	2D:4D ratio
Human average	normal	0.98	0.76	0.78	3D>4D>2D>1D>5D	0.96
_Genetic sub-population:
Males	XY	0.95	0.75	0.79	3D>4D>2D>1D>5D	0.95
Females	XX	1.01	0.77	0.77	3D>4D>2D>1D>5D	0.97
Achondroplasia	FGFR3 gene	0.70	0.66	0.95	3D>4D>2D>1D>5D	0.96
Down syndrome	Trisomy 21	0.87	0.70	0.81	3D>4D>2D>1D>5D	0.96
Fragile-X syndrome	Xq27.3 gene	0.89	0.78	0.88	3D>4D>2D>1D>5D	0.96
Marfan syndrome	FBN1 gene	1.21	0.81	0.67	3D>4D>2D>1D>5D	0.96

PRIMATE HANDS IN THE NEWS

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