Once the Solomani Hypothesis (which theorized that all humaniti came originally from Terra) was accepted, it was a simple matter to analyze the gene pools available to each of the distinct human races found on worlds other than Terra. Those studies have concluded that the Ancients visited Terra many times, taking groups of between 1,000 and 10,000 humans to each of perhaps 100 planets.
The reason for Ancient interest in humaniti is unknown. Theories involving humans as slaves, assistants, workers, even as pets have been advanced, but there is not enough evidence to support any specific conjecture.
The three most widespread human races are the Solomani (humans from Terra), the Vilani (humans from Vland), and the Zhodani (humans from Zhodane).