Scientists Trace Humans Fishy Origins

Neil Shubin, professor of Anatomy at Chicago University is due to publish a new book which explores the links between the osteology of humans and links to their ancient ancestors; the first fish and amphibians.

Using evidence related to the evolution of fishes and the first land living vertebrates, Shubin demonstrates that many of the traits associated with H. sapiens, traits thought unique to us, have their origins in animals that lived hundreds of millions of years ago.

Professor Shubin and his team reinforce the believe that the origin of human hands and digits lie in the emergence of the lobe-finned fish in the middle of the Devonian period.  Lobe-finned fish, more precisely described as Sarcopterygians, were so called as their fins sprouted from muscular lobes supported by bone.  Indeed, Shubin heralds Eusthenopteron (means “good strong fin”), a lobe-finned fish of the late Devonian as evidence of the development of upper arm bones such as the humerus.

A Fossil Eusthenopteron

Picture Credit: Parc National de Miguasha

This fossil Eusthenopteron (head is pointing to the right), shows the scales and the typical tail fin arrangement so typical of this group of primitive fishes.

His team go on to cite a number of examples from the fossil record that indicate that the majority of the human genome (the instructions or blueprint for making a person), evolved millions of years ago.  Study of an ancient sea creature, a Tiktaalik (fossils discovered in the Arctic in 2003), may provide a clue to the origin of our shoulder and arm joints.

Interestingly, many of the early Tetrapods such as Acanthostega and Ichthyostega had many more digits than humans.  This may be a legacy of the digits first evolving to help water based creatures clamber over vegetation in the shallows rather than for supporting body weight for movement around on land.

Close study of early amphibian fossilised vertebrae can show evidence of vertebral pegs called zygapophyses.  These helped stiffen the back bone and allowed early Tetrapods to carry their bodies off the ground.  Front and rear zygapophyses can still be found in human vertebrae today – another legacy from our fishy origins.

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