Abstract

In 1835, as a young naturalist on board the Beagle expedition exploring the delights of South American flora and fauna, Charles Darwin encountered a tiny new barnacle off the coast of Chile that he found most curious. Unlike all the usual shelled species found attached to rocks or even ship hulls, this one lived “naked,” sheltered in the crevices of seashells. “Mr Arthrobalanus,” as he dubbed the unusual little creature, continued to intrigue Darwin far beyond the initial discovery. Little did he know that some 10 years later he would embark on a 6-year-long taxonomic project that not only described and classified Mr. Arthrobalanus but also all other known cirripede species, both living and fossil. Nor could he imagine that in undertaking this endeavor, he would not only cement his reputation as an eminent naturalist but also test his developing ideas about the evolution of life on Earth. This chapter reveals how Darwin’s study of barnacles sheds essential light on many foundational evolutionary tenets laid out in his next major work: On the Origin of Species (1859).