The Opposable Thumb

The opposable thumb has played a key role in human evolution:

A discussion of primate characteristics is often included during units on human evolution. One of the characteristics most often identified as being typically primate and having played a role in human evolution is the opposable thumb. It is argued that the eye-hand coordination made possible by both stereoscopic vision and a grasping hand permitted primates to exploit arboreal habitats in a more efficient fashion. That same hand is used by humans today to manipulate tools and, in turn, the environment with a great deal of dexterity.

Recent research has shown that the evolution of the opposable thumb was not unlikely:

An ancestor of mammals first took to the trees before the age of dinosaurs, evolving the first known opposable thumbs on the way, a group of Toronto researchers reports.

The animal, dubbed Suminia getmanovi, lived at a time when other known vertebrates, including both predators and plant-eaters larger than itself, spent all their time on the ground, said University of Toronto paleontologist Robert Reisz, who studied its complete fossil remains with his PhD student Jörg Fröbisch.

“This is a small plant eater that was not only able to get away from the predators by climbing into the trees,” Reisz said in an interview Tuesday, “but also to access an untapped food resource — that is, the leaves of the trees.”

How might one help to front-load the evolution of an opposable thumb? Front-load the appearance of the pentadactyl limb and front-load the appearance of trees. From there, it’s just a matter of time.

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2 responses to “The Opposable Thumb

  1. Nick (Matzke)

    Two points:

    1. Generic opposable thumb != humans’ specific opposable thumb, which I guess can do a few things other primates’ thumbs can’t.

    2. I don’t see why pentadactyl-ity or thumbs have much to do with it, various birds with fewer toes have evolved opposability for perching, woodpeckers have special arrangement for trunks, chameleons have 2 “thumbs” in a 3-2 split, etc.

    So all you really can say is, yeah, trees encourage opposable digits. Thus proving that God specially constructed the biosphere so as to front-load woodpeckers, of which there are far more species than there are of humans.

  2. Hi Nick,

    Can you make the case that humans were as likely to evolve without trees? As I see it, a planet with trees is more likely to evolve a human-like entity than a planet with no trees.

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