Do any primates have opposable thumbs?
Napier and Napier define opposition as: “A movement by which the pulp surface of the thumb is placed squarely in contact with – or diametrically opposite to – the terminal pads of one or all of the remaining digits” While an opposable thumb is one of the hallmarks of humans, it is not unique to the species. What is unique to Homo sapiens sapiens is the broad area of the contact achieved between the compressible pulps of the index finger and thumb. Not all primates are capable of opposing their thumbs. The necessary movement for true opposability is the rotation of the about its own long axis. Without this rotation the movement of the thumb towards the palm is a form of pseudo-opposability where pulp-to-pulp contact of the thumb and digits is not possible. Source: Napier and Napier. The Natural History of the Primates. MIT Press, 1985. There are four categories of thumb movements determined by the degree of independence of the thumb. They are: 1) Non-opposable thumbs.
Napier and Napier define opposition as: “A movement by which the pulp surface of the thumb is placed squarely in contact with – or diametrically opposite to – the terminal pads of one or all of the remaining digits” While an opposable thumb is one of the hallmarks of humans, it is not unique to the species. What is unique to Homo sapiens sapiens is the broad area of the contact achieved between the compressible pulps of the index finger and thumb. Not all primates are capable of opposing their thumbs. The necessary movement for true opposability is the rotation of the about its own long axis. Without this rotation the movement of the thumb towards the palm is a form of pseudo-opposability where pulp-to-pulp contact of the thumb and digits is not possible. Source: Napier and Napier. The Natural History of the Primates. MIT Press, 1985. There are four categories of thumb movements determined by the degree of independence of the thumb. They are: 1) Non-opposable thumbs. Examples: tarsiers
