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Cartilaginous skeleton not necessarily more “primitive”

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Squalus acanthias stellwagen.jpg
spiny dogfish (Squalus acanthias)

A friend writes to tell us of an insightful article in Nature:

It emerges that a dogfish shark’s spine becomes stiffer as the fish swims faster, enabling the animal to swim efficiently at different speeds. The finding could also provide inspiration for the design of robotic biomaterials. (paywall) – Biomaterials: Sharks shift their spine into high gear
Matthew A. Kolmann & Adam P. Summers, Nature, 14 December 2016 | doi:10.1038/nature21102, More.

The friend believes that the shark’s cartilaginous skeleton should not be thought of, as it often is, as primitive, but as an intelligent use of materials that enable high-speed bursts of movement. As the author put it, the skeleton is “an aquatic equivalent of continuously variable transmission, a type of gear-change system found in some motor scooters that is continuously responsive to a wide range of speeds.”

And the cartilage? “It is a type of in-between substance, neither an elastic solid such as rubber or metal, nor a stirrable fluid such as coffee. Instead, cartilage belongs to the category of viscoelastic materials – materials that resist deformation differently when they change length at different rates.”

The authors naturally hope to apply their newfound knowledge to biomaterials. In the meantime, one wonders how many opportunities have been lost to an artificial “tree of life” way of thinking about nature in which, in the hierarchy of the old-fashioned tree of life, bone was just plain better, “more evolved,” somehow.

Is “primitive” one of those phrases, like living fossil, that implies a scenario that, once accepted, need not actually be demonstrated?

Some use the term durable species for living fossils; less colorful but more accurate.

What would a better term than “primitive” be?

See also: Human hand more primitive than chimps’?

Sneezing sponges – existence challenges assumptions about ‘primitive’ organism

and

Sharks not primitive? Well, if they aren’t, what is?

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2 Replies to “Cartilaginous skeleton not necessarily more “primitive”

  1. 1
    bornagain77 says:

    of related note:

    Shark and human proteins “stunningly similar”; shark closer to human than to zebrafish – December 9, 2013
    Excerpt: “We were very surprised to find, that for many categories of proteins, sharks share more similarities with humans than zebrafish,” Stanhope said. “Although sharks and bony fishes are not closely related, they are nonetheless both fish … while mammals have very different anatomies and physiologies.
    http://www.uncommondescent.com.....zebrafish/

  2. 2
    tjguy says:

    It emerges that a dogfish shark’s spine becomes stiffer as the fish swims faster, enabling the animal to swim efficiently at different speeds.

    The friend believes that the shark’s cartilaginous skeleton should not be thought of, as it often is, as primitive, but as an intelligent use of materials that enable high-speed bursts of movement.

    Another evolutionary assumption bites the dust! Another instance of the evolutionary paradigm leading the scientist down the wrong trail.

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