Charles Darwin was fascinated by earthworms and carried out many experiments on them. He noticed that they drag leaves into the openings of their burrows and that most of these leaves were drawn into the tunnel by their tips. This was the most efficient way to do it and he wondered if the worms were actually making choices about the best way to accomplish the task.
Darwin experimented by placing paper triangles near worm burrows. He used paper triangles to rule out natural instinct or some kind of chemical interaction. He found that far more triangles than could be explained by chance had been drawin into the burrow by their apex and he reasoned that the worms were therefore deciding the best place to grip the triangle in order to successfully pull it into their burrow.
However, Darwin hadn’t actually ventured out at night and watched the worms in action. A naturalist called Hermann Jordan did in 1913.
He found that a worm would grasp the first object it came into contact with and try to drag it into its burrow. If it was unsuccessful it would let go and try again in another spot on the leaf. Eventually it might get hold of a point near the leaf’s apex and manage to drag it into the burrow.
So when Darwin saw that most of the paper triangles had been drawn into the tunnels by their apex that was the result of trial and error and persistence by the worms. He was seeing their successful results not the previous attempts.
Natural History Museum
Wikipedia
Natural History Magazine
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