Size Matters

When I was in college I had the amazing fortune to take a course with paleontologist, evolutionary biologist, and science historian Stephen Jay Gould. His lectures were entertaining, fascinating, fact-filled, and completely accessible to non-science majors. He instilled in me a lifelong love of quirky science, and especially the history of science. I remember one of his lectures opened with this image:667px-Attackofthe50ftwomanThe subject of the class was about size and shape, and the relationship of surface to volume. All animals, from a tiny gnat to a giant seismosaurus, are shaped to their advantage by natural selection. They assume sizes and shapes that allow them to adapt best to their environment, and they are ruled by gravitational forces. If an animal grew larger but kept the same shape, there would be a decrease in relative surface area, because volume grows more rapidly than does surface area.

ants3That’s why a fifty-foot woman is impossible, at least proportioned the way she is in the movie. She’d have to have massive legs to support her increased volume. And it’s why so many of my favorite sci-fi films about killer bugs that grow to be the size of a school bus are–spoiler alert!–impossible. The reason huge animals like whales can exist is that they live in a nearly weightless water environment. On land, smaller animals  must remain small because if they grew larger, their volume would increase more rapidly than would their surface area, and their legs would not be able to support their weight without thickening considerably (think of the legs of an elephant or a rhino).

WW1The large insects in these films could never walk up walls or fly. As Gould points out,  “…the ability to fly depends upon the surface area of the wings, while the weight that must be borne aloft increases as the cube of length.”

So don’t worry. It’s only a movie.MV5BODA1MjY0MDI4OV5BMl5BanBnXkFtZTcwNzQ4ODA0MQ@@._V1._SY317_CR310214317_ MV5BMTg4NTE2MTUzN15BMl5BanBnXkFtZTYwMTI4MDg4._V1_SY317_CR3,0,214,317_ 936full-beginning-of-the-end-poster2-163x250images

 

Source: Gould, S.J. 1974. Size and Shape. Nat. Hist. 83: 20 – 26

5 Comments

  1. LInda Baie

    Sarah, I love all your books, & this is such an interesting & fun post. Perfect for a math lesson, figuring out what “would” work, or how things would need to change in order to “work”. Thanks a lot!

    Reply
  2. Barbara Jean Champ

    I just love the movie Them-truly its one of my favorites and best in it’s genre-I visited your site because I was looking for books about the history of color- I will get your book about the color purple. Thanks for your creativity-keep it coming and I won’t join Twitter!!

    Reply
    • Sarah Albee

      Thanks, Barbara–I’m a big fan of Them as well. The “color purple” book will be out next year. Still doesn’t have a title but it’s with National Geographic Kids.

      Reply

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