Darwin sailed on the Beagle mainly to keep the captain company at dinner

Charles Darwin wasn't hired as the HMS Beagle's official naturalist — that job belonged to the ship's surgeon. Captain Robert FitzRoy, worried about the isolation that had driven his expedition's previous captain to suicide, wanted an educated gentleman companion of his own class to dine with. Darwin's five years aboard reshaped biology anyway.

— Charles Darwin, Voyage of the Beagle — Journal published 1839; FitzRoy's invitation, 1831