Human Design is usually described as a synthesis of four older systems. The Manifestor, and the typology it belongs to, is the part that came from none of them.
What was borrowed and what was not
The sixty-four gates come from the I Ching, which has sixty-four hexagrams. The nine centres are adapted from the chakra model, which classically has seven. The method of calculation is astrological. The Tree of Life supplies a connective structure.
None of those four systems classifies people into five kinds. The I Ching does not; astrology has typologies but not this one; the chakra model describes a structure said to be common to everyone rather than a set of variants. The fivefold typology is Ra Uru Hu's own, published in 1987, and it is the layer of the system that has the least claim to descend from anything.
That is worth stating plainly, because the value people place on Human Design often rests on its perceived antiquity, and the part most used in practice is the part with the shortest history.
How a type is arrived at
A type is read off the pattern of activated connections in a chart calculated from a birth time. The rule is mechanical: the same birth data always yields the same type.
What has not been shown
No independent test has established that people sorted by this typology differ in the ways the system says they do. The atlas records the system as its author set it out and does not present it as established fact.