Dung beetle discovery revises biologists' understanding of how nature innovates

NOVEMBER 21, 2019 

by Indiana University

When studying how organisms evolve, biologists consider most traits, or features, as derived from some earlier version already present in their ancestors. Few traits are regarded as truly "novel." 

Insects were wingless, then winged. Animals were blind, then had eyes. 

And in biology textbooks, novelty has a strict definition: it must have no relationship to any structure found in an ancestor and no relationship to any other body part elsewhere in the organism. By this definition, a dolphin's pectoral fins are not a novelty because they are modified forelimbs that already existed. 

However, some experts argue this creates a problem since it means novelty must seemingly arise from nothing. It must "pop up out of the blue" in evolutionary time. 

Now evidence has emerged—in a study published Nov. 21 in the journal Science—that illuminates how new things can evolve. Moreover, this evidence has come from an unexpected source: the small, yet charismatic dung beetle. 

"Dung beetles are fascinating creatures," said Armin Moczek, the study's senior author and a professor in the IU Bloomington College of Arts and Sciences' Department of Biology. Among their many qualities, one structure has placed them at the forefront of discussions about novelty among researchers. That structure is their thoracic horn, which is regarded as a textbook example of an evolutionary novelty. This is because the thoracic horn is unique to horned beetles, and it appears to have no relationship to any other structure in the animal. 

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