A hypothenar whorl in the right hand of a macaque (macaca fascicularis), source: 'Dermatoglyphics: an international perspective', p.58 (Mavalwala, 1978).
NOTICE: The macaque hand example above demonstrates some typical features of the primate hand, including: (1) a very short thumb; (2) a low 2D:4D finger ratio; (3) a simian line-like palmar transverse crease; and (4) various palmar whorls.
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While the 'hypothenar whorl' is rare in the human hand, in the primate hand it is a common feature - the primate hand example on the right has 5 palmar whorls, including the 'hypothenar whorl'!
Primate hand examples in the work of Cummins & Midlo (1943) indicate that in primates the 'hypothenar whorl' is most common in 'promsimians' (present in 3 out of 4 example); less common in 'Old & New world monkeys' (present in 3 out of 14 examples)and least common in the 'human apes' (present in 3 out of 24 examples).
Interestingly, studies in various primate species indicate that there is a 'reversed' evolutionary link between the occurence of palmar patterns (loops and whorls) and the advance of (motoric) specialization ('Quantitative dermatoglyphics', p.98, D.Z. Loesch, 1943) - see the figure below.
Likely, this is a very important point to notice, in order to understand the 'nature' of palmar whorls!
For, this 'primate hand pattern' indicates that - next to the famous simian crease - 'palmar whorls' as well should be recognized as a potential 'problematic' hand characteristic! [Notice: in medical science the 'simian line' is recognized as a minor physical anomaly (MPA)]
The distribution of palm & sole patterns in primates and humans, source: 'Finger prints, palms and soles', p.174 (H. Cummins & C. Midlo, 1943).
NOTICE: The primate species described in figure above are (right to left): 'Homo'=human; 'Pan'=chimanazee, 'Gorilla'=gorilla, and 'Pongo'=orangutan (the 3 'human ape' primates); the next 15 species are 'New & Old world monkeys' (starting with: 'Hylobates'=gibbon); and the last 4 primates species are known as 'prosimians' (tarsius to lemur).
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