Once upon a time in 1837, after returning from his 5-year trip aboard the Beagle, Charles Darwin took some time off. One day, while roaming the countryside with his uncle, they stopped to watch an earthworm s-l-o-w-l-y pull a leaf into its burrow. Fascinated, Darwin fell in love with worms. How could such a lowly creature capture the attention of a distinguished scientist like Darwin?

NOTE: You’ll find the answer in Amy Stewart’s award-winning book called, The Earth Moved, which, I must say, is delightful and charming. Published by Algonquin Books, Amy's book would turn anyone into an earthworm lover.

[Special note: I've recorded a 3-minute radio show, a condensed version of this article. To hear it, you can subscribe to my podcast feed (so you can open the attachment below) or you can listen to the mp3 file now by clicking here]

Otherwise, keep on reading. Enjoy! 


Worms interested Darwin for decades. He even devoted his last book to a detailed research of worm biology and behavior. At night, Darwin would watch earthworms emerge from their burrows and draw in twigs and leaves, (which says something about the guy's social life).

PAPER TRIANGLES

To evaluate earthworms, Darwin took an ingenious, almost playful approach to experimentation. In the case of studying earthworms and their burrows, the naturalist cut out tiny paper triangles and set them near burrow entrances. Then he charted the number of times the triangles were drawn in by the apex, the middle, or the base.

It was this kind of research that pleased the elderly man. “There is no doubt that he took some pleasure in his work,” writes Stewart. “He had a genuine fondness for the worms and seemed to enjoy the painstaking effort that his research required.

“In the waning years of his life, he was sometimes weak and infirm, but that only turned the attention of his scientific mind away from the wider world and towards his home, his garden, and the earth.”

THE GARDENER-SCIENTIST

As one biographer wrote: “[Darwin] became in the end what he had always been in his heart, almost a part of nature himself, a man with time to lean on a spade and think, a gardener.”

Darwin was the first describe how earthworms tilled the soil, swallowing and ejecting soil as castings, or worm manure. He estimated that an acre of garden soil could contain over fifty thousand earthworms and yield eighteen tons of rich, organic castings per year. (Darwin was a tad short on his estimate. Scientists now figure worms can number one million wigglers per acre.)

All this during a time when scientists were still asking simple questions like, where does soil come from? And not long before, in the mid 1700s, many believed that plant roots had little mouths and ate soil particles.

IF THOMAS JEFFERSON DID IT,
IT MUST BE OK, RIGHT?

“Believing that loose soil consisted of smaller particles that would more easily fit into root mouths,” writes co-author, Jeff Lowenfels in Teaming With Microbes (published by Timber Press), inventors of the day developed a horse-drawn hoe to till and churn the soil. The theory that chopped up soil yielded better harvests caught the attention of gentlemen farmers like George Washington and Thomas Jefferson, “who encouraged their fellow Americans to break up soil.”

Soil quality has been going downhill ever since, because today, most home gardeners still break up and turn over their soil at least annually, “even though we know plant roots don’t eat soil,” chides Lowenfels, in his classic tongue-in-cheek way. (Though he often dons a red nose for public appearances, Jeff is serious about microbes.)

What’s so bad about rototilling? Rototilling and excessive soil disturbance destroys or severely damages the structure of the soil, from the “highways” created by earthworms, to the miles of root hairs and the network of fungi in the soil. Over time, the soil compresses. Plants suffer, unable to obtain nutrients, and erosion occurs, as evidenced by the millions of tons of topsoil that flows down the Mississippi River into the ocean. [To learn more about the downside of rototilling, read my article, Why Roto-tilling is a No-No.]

THE APEX WINS!

But, I digress. As for the paper triangle experiment, Darwin did not simply cut a few triangles and sprinkle them around. According to Stewart, “He cut 303 triangles of various sizes and coated them with fat to keep them from going limp in the night dew.” Darwin’s findings: The worms drew the paper triangles in by their apex 62 percent of the time.

Darwin considered earthworms as one of our planet’s most important caretakers. “I doubt,” he said, “whether there are many other animals which have played so important a part in the history of the world, as have these lowly organized creatures.”

Not bad for an animal that’s deaf, blind, and spineless.