Evolution Gone Wrong: The Curious Reasons Why Our Bodies Work by Alex Bezzerides

Author:Alex Bezzerides [Bezzerides, Alex]
Language: eng
Format: epub
ISBN: 9781335690050
Amazon: 1335690050
Publisher: Hanover Square Press
Published: 2021-05-17T23:00:00+00:00

Oozed Discs

Our troublesome intervertebral discs have quite the backstory. The cartilaginous discs have a soft, gel-like central portion, called the nucleus pulposus, surrounded by a tougher outer ring called the annulus fibrosus. Analysis of the cells from the nucleus pulposus has revealed that portions of this softer, squishier section of an intervertebral disc are derived from the notochord.12

If you have ever taken a biology class, you have the word notochord tucked somewhere within the recesses of your brain. I review the concept in just about every class I teach when we go back over the taxonomic classification of humans. All organisms are classified into a handful of kingdoms (e.g., bacteria, plants, animals), and then those kingdoms are further subdivided into phyla. There are 36 recognized phyla of animals. Most of them you’ve never heard of, unless you’re into super obscure animals like mud dragons, penis worms, and water bears. I mean, I don’t pretend to know your life, but I’m betting you haven’t spent a lot of time thinking about penis worms.

One important phylum students seem to struggle to remember is our own phylum. Very few people, including those who have learned it before, remember we are members of the phylum Chordata. Even though most of the animals we know and love, including fish, amphibians, reptiles, birds, and all other mammals, are in the phylum Chordata, the term has not caught on like other popular classifications such as mammal, primate, or vertebrate. Even though it is our phylum, it proves more challenging for students to recall than other phyla like Mollusca or Arthropoda. Chordata has a serious branding problem.

The defining feature of chordates is the presence of a notochord. The notochord is a beam of tissue that provides a longitudinal structure for the development of a chordate. I will grant you the concept is not as sexy as mammary glands, which give the class Mammalia its name, and maybe this is why nobody remembers we are chordates. The Chordata PR firm has to work with a flexible rod instead of dazzling lumps of tissue that make milk. That’s not really a fair fight in terms of what people will remember. Notochords have ancient origins and are present in a few very simple organisms like sea squirts, which I have always found quite humbling to have in my same phylum.

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