How Barnacles Baffled Biologists for So Long

PBS Eons host Kallie Moore explains how the elusive barnacle baffled biologists for many years despite their immense ubiquity in maritime environments,

They’re found in virtually all marine environments, stubbornly attached to any surfaces they can find – from rocks and boats to whales and turtles. They may not look like much, but beneath that shell lies an evolutionary mystery – one that stumped the biggest names in natural history for over a hundred years.

Included in this list of scientists was Charles Darwin, who set out to study this symbiotic creature for a year and found himself spending almost eight years on the project. No matter how he dedicated himself, however, he remained woefully confounded by the creature’s classification.

Some of the most influential biologists of their day grappled with the challenge of working out what they actually are and where they fit in the tree of life, only to be proved totally wrong. Others were almost broken by the attempt – including Charles Darwin, who embarked on an eight-year-long personal side-quest to figure them out. By year six, he wrote to a friend, “I hate a Barnacle as no man ever did before”.

The barnacle eluded specific scientific classification due to its similarities, to both mollusks and crustaceans. Previous scientists had put them in the mollusk category. Another scientist, however, William Thompson, subsequently believed them to be crustaceans. Darwin, despite his frustrations with the creatures, found evidence that agreed with Thompson’s analysis.

Despite being so frustrated by these creatures that he found himself wishing that they never existed – a feeling familiar to many graduate students – Darwin did eventually see the end of his work. His detailed analysis of modern and extinct species is still important to the study of barnacles today. He helped confirm Thompson’s radical reclassification of barnacles as a branch of the crustacean family tree, and they’ve stayed there ever since.