51:4.1 The race of dominance during the early ages of the inhabited worlds is the red man, who ordinarily is the first to attain human levels of development. But while the red man is the senior race of the planets, the succeeding colored peoples begin to make their appearances very early in the age of mortal emergence.
51:4.2 The earlier races are somewhat superior to the later; the red man stands far above the indigo—black—race. The Life Carriers impart the full bestowal of the living energies to the initial or red race, and each succeeding evolutionary manifestation of a distinct group of mortals represents variation at the expense of the original endowment. Even mortal stature tends to decrease from the red man down to the indigo race, although on Urantia unexpected strains of giantism appeared among the green and orange peoples.
51:4.3 On those worlds having all six evolutionary races the superior peoples are the first, third, and fifth races—the red, the yellow, and the blue. The evolutionary races thus alternate in capacity for intellectual growth and spiritual development, the second, fourth, and sixth being somewhat less endowed. These secondary races are the peoples that are missing on certain worlds; they are the ones that have been exterminated on many others. It is a misfortune on Urantia that you so largely lost your superior blue men, except as they persist in your amalgamated "white race." The loss of your orange and green stocks is not of such serious concern.
51:4.4 The evolution of six—or of three—colored races, while seeming to deteriorate the original endowment of the red man, provides certain very desirable variations in mortal types and affords an otherwise unattainable expression of diverse human potentials. These modifications are beneficial to the progress of mankind as a whole provided they are subsequently upstepped by the imported Adamic or violet race. On Urantia this usual plan of amalgamation was not extensively carried out, and this failure to execute the plan of race evolution makes it impossible for you to understand very much about the status of these peoples on an average inhabited planet by observing the remnants of these early races on your world.
51:4.5 In the early days of racial development there is a slight tendency for the red, the yellow, and the blue men to interbreed; there is a similar tendency for the orange, green, and indigo races to intermingle.
51:4.6 The more backward humans are usually employed as laborers by the more progressive races. This accounts for the origin of slavery on the planets during the early ages. The orange men are usually subdued by the red and reduced to the status of servants—sometimes exterminated. The yellow and red men often fraternize, but not always. The yellow race usually enslaves the green, while the blue man subdues the indigo. These races of primitive men think no more of utilizing the services of their backward fellows in compulsory labor than Urantians would of buying and selling horses and cattle.
51:4.7 On most normal worlds involuntary servitude does not survive the dispensation of the Planetary Prince, although mental defectives and social delinquents are often still compelled to perform involuntary labor. But on all normal spheres this sort of primitive slavery is abolished soon after the arrival of the imported violet or Adamic race.
51:4.8 These six evolutionary races are destined to be blended and exalted by amalgamation with the progeny of the Adamic uplifters. But before these peoples are blended, the inferior and unfit are largely eliminated. The Planetary Prince and the Material Son, with other suitable planetary authorities, pass upon the fitness of the reproducing strains. The difficulty of executing such a radical program on Urantia consists in the absence of competent judges to pass upon the biologic fitness or unfitness of the individuals of your world races. Notwithstanding this obstacle, it seems that you ought to be able to agree upon the biologic disfellowshiping of your more markedly unfit, defective, degenerate, and antisocial stocks.