Gravitelamo (Latin for heavy weapon man), more commonly called the Heavies, describes the family that consists of some of the larger members of the TF2 ecosystem. The first Heavies came from Russia, and migrated worldwide over the course of millions of years. The Heavies are known for their size and strength, and are some of the largest TF2-nimals known to date.
According to recent expeditions in cp_pootis land, the Gravitelamo family may be the oldest. The root classes all lived together long ago; however, the Gravitelamo family had already evolved into "Pootisbirds". This proposes that the 8 other classes all stemmed from the Gravitelamo, which was a direct descendant of the original Citizen.