More on vestiges

In the previous post, I pointed to a site that lists the “Top 10” vestigial organs. Number of 9 on this list has long been my personal favorite: the vestigial pelvic bones of modern whales. The reason it is my favorite is because of the role that it played in my own intellectual development.

From an early age, I have been fascinated by nature, and by animals in particular. When I was growing up, my family moved around a lot, but we always lived on the suburban fringe of one midwestern city or another, with easy access to woods, fields, and streams. My parents being tolerant of unsupervised wandering to a degree that was common then, but uncommon today, I would spend a lot of my free time exploring the tiny slices of nature available to me. When I was five, we lived in Fort Wayne across the road from a one-acre woodlot which seemed as vast and as bountiful as the great deciduous forests of eastern North America must have seemed to European settlers. At seven, in Finneytown (outside Cincinnati), I would bring home jars overfilled with tadpoles, unwittingly doing cruel experiments on the carrying capacity of pondwater microcosms. At 9, in Kenwood (a different Cincinnati suburb), there was a stream that my friends and I would follow to “Devil’s Dungeon” (a huge storm drain). Splashing through the stream we would find crayfish, frogs, turtles, and even a medicinal leech on one occasion.

There wasn’t much to these discoveries beyond the general show of admiration that young kids offer to things they are seeing for the first time, but they did feed my growing appreciation of the wonders of nature. And not just the extant wonders of nature. When on family picnics to various parks around the Cincinnati area, we would find stream beds that abounded in fossil creatures, most of which, I now realize, were bryozoans that must have lived about 440 million years ago (see this reference). I can still recall the sense of wonder I felt as I fondled these pieces of matter that once had lived and now were rock.

Then there was Mr. Terwilliger, my fifth grade science teacher. I LOVED science class–electroplating pennies with nickel, looking at dead insects through a microscope, but especially watching live animals in Mr. T’s classroom. He had a menagerie of snakes, snapping turtles, deer mice, white mice (who were there mainly to be food for the snakes), and crayfish (for the snapping turtles). It was around this time that I asked my mother, who had been a botany major in college, “If botany is the study of plants, then what is the study of animals?” When she told me “Zoology,” that’s when I decided to become a zoologist. That was before I decided I wanted to be an NFL football player, preferably a member of the Green Bay Packers under Vince Lombardi, a dream that had to be relinquished when I turned out not to grow up to six foot four and 250 pounds as I had planned. Fortunately zoology worked out as a decent backup plan.

I read a lot as a child, and I was particularly drawn to books about nature and science. I learned about vestigial whale bones in one of these books, again when I was around 10. I think it was by Roy Chapman Andrews, the great paleontologist and longtime director of the American Museum of Natural History, who wrote for children as well as for a professional audience and the general public. What I remember of the story is its essential logic.

  • Whales are mammals through and through, though they look more like fish than they do like other mammals.
  • Mammals originated on land, so the ancestors of whales must have been terrestrial and not aquatic creatures, and must have had four legs like other mammals.
  • Whales have a lot of features that terrestrial mammals do, including hair, lungs, and forelimbs (their flippers) with five digits.
  • Perhaps they also have traces of hind limbs even though none are visible on the surface.

The book then described how some scientist (the author? someone else?) arranged to dissect a whale that had washed up on a beach. Rooting through the blubber, he finds them, in just the spot where one would expect: bones equivalent to those in the pelvic girdle in mammals that walk on land. They were in the right location, they had the right shape, but they were now rudiments of the legs that they had descended from, with no function related to walking.

This absolutely floored me. I recall being completely amazed not so much by the facts that were revealed about nature, but by the power of human reasoning that was on display: that you can ask a question about the distant past (whether the ancestors of whales had hind legs), and then figure out a way to answer it.

It still amazes me.

____________

Updated to correct broken link: http://www.livescience.com/11317-top-10-useless-limbs-vestigial-organs.html

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About ethologist

Professor in the Zoology Department at Michigan State University
This entry was posted in Becoming a scientist, Evolution, Nature of science. Bookmark the permalink.

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