TMA-0 was a large, black, crystalline monolith, placed on the Earth by a mysterious alien race in the year 4 million B.C. It was the first and only monolith placed on the Earth.
TMA-0 was used as a catalyst for the evolution of intelligence.
TMA-0 was first discovered by a tribe of ape-men, on the brink of starvation. The monolith probed their minds, and, through some unseen force, altered their brains and instigated their evolution into modern man. It disappeared after three days.
It was later discovered by humans in the year 2513; unearthed in a gorge in Africa.
In accordance with the other monoliths (except the Europa monolith, which may, in fact very well have been TMA-2, but this was never proved), the Africa monolith was given a "TMA" designation, albeit found on Earth, rather than the moon, let alone Tycho, and possessing no magnetic field.
It was named TMA-0, rather than TMA-3, because it, despite being the third monolith discovered by modern man, it was the first to come in contact with our evolutionary ancestors.