Reader Comments

Post a new comment on this article


Posted by pbio on 07 May 2009 at 22:11 GMT

Author: C.Jairaj Kumar
Position: Dr.
Institution: Kasturba Medical College, Mangalore
Submitted Date: October 30, 2005
Published Date: October 31, 2005
This comment was originally posted as a “Reader Response” on the publication date indicated above. All Reader Responses are now available as comments.

I would like to congratulate the authors on their discovery of tool usage among wild gorillas. Observational studies on tool usage and manually dexterous activities yield important clues for understanding primate evolution. In response to this article I would like to draw your attention to our observation regarding tool usage in humans, which we believe may help enhance our knowledge of human and primate evolution. The main factor responsible for the digital dexterity and the use of tools by humans is their unique ability to oppose the thumb to the pulp of their fingers. Thus they can perform dexterous activities like untying knots, threading needles and tearing paper without the use of their orofacial appendages. All primates (gorillas, orangutans and chimpanzees), with the exception of human beings, lack the ability to oppose the thumb to the pulp of their fingers and circumvent this deficiency by using their orofacial appendages to perform dexterous tasks.
Although human beings no longer require the use of their orofacial appendages to perform dexterous task, It is our observation, confirmed over the years, that the higher the degree of digital dexterity involved in the performance of a manual task (like untying a knot, threading a needle), more pronounced is the involuntary orofacial response to the degree of concentration the task requires. We strongly believe that this involuntary orofacial response to dexterous activities is an odd non-anatomical, physiological atavistic trait present in humans.


1.Breuer T, Ndoundou-Hockemba M, Fishlock V (2005). First observation of tool use in wild gorillas. PLoS Biol 3 (11) : e 380.

2. Kumar A, Kumar JC. Atavistic orofacial response to manually dextrous activities. Med Hypotheses 2005; 65 (1):196.

Competing interests declared: I have no competing interests.