The Golgafrinchans were a race of humanoid beings who split their population into three distinct groups and sent their third group, the middlemen, on a spaceship which eventually ended up on planet Earth. The Golgafrinchans were later revealed to be the true ancestors of humans, instead of apes. Arthur Dent and Ford Prefect materialised inside Ark Fleet Ship B, where they met the Golgafrinchan Captain, and later lived with the other middlemen for a short period of time on pre-historic Earth.
As well as the Captain and his first and second in command, several members of middle management from Golgafrinchan are encountered by Arthur and Ford during their time with them. These include a management consultant, a woman working in marketing, a hairdresser, a producer named Finlon, and at least one life insurance salesperson. While on Earth - which the Golgafrinchans named Flintlewoodlewix - there were at least two committees created: the "Colonisation Committee of the Planet of Fintlewoodlewix" and the "Hairdressers Fire Development Subcommittee", which both contained self-appointed chairpeople.
The Golgafrinchans realised that were three types of beings on the planet of Golgafrincham: the leaders (or thinkers), the workers (or doers), and the middlemen.
The leaders contained the artists and "achievers". The workers were the people who "did all the actual work", and who made and did things. The middle management was comprised of hairdressers, telephone sanitisers, and other such "worthless jobs."
The group of leaders built a ship and convinced the middlemen to leave Golgafrincham by telling them several different reasons, including: that the planet was going to crash into the sun (or perhaps the moon was going to crash into the planet), that the planet was being invaded by a gigantic swarm of twelve foot piranha bees, and that "the entire planet was in imminent danger of being eaten by an enormous mutant star goat."
The middlemen were sent off, told that the other Golgafrinchans would follow soon, however they remained on the planet with no intention of leaving. The middlemen stayed in space for a long period of time, with many on board in suspended animation for the majority of the journey, with the exception of the Captain and his Number One and Number Two. This third class eventually crashed onto Earth, while the other two-thirds of their society on Golgafrincham lived full, rich and happy lived until they were all suddenly killed off by a raging disease contracted from a dirty telephone.
Eventually, while sustaining major losses, and settling down in a cave-dwelling lifestyle, becoming 'cavemen', the Golgafrinchan middlemen wiped out the hut-dwelling original humans of Earth, and became the ancestors of present day humanity, "mucking up the program to determine the Ultimate Question."
The Great Circling Poets of Arium
The Golgfrinchans included the mysterious figures of the Great Circling Poets of Arium. The Circling Poets used to live in remote mountain passes where they would lie and wait for small bands of unwary travellers, circle round them, and throw rocks at them. When the travellers spoke to them, the Poets would then sing a long and beautiful song.
It was a descendent of these eccentric poets who invented the tale of impending doom which enabled the people of Golgafrincham to rid themselves of an entire "useless third" of their population.