Besides this, a great mass of the animal kingdom of the Moon-chain was surging up to the level of the individualization, and some of its members had already reached it, while many others had not.

These latter needed further animal incarnations upon the Earth-chain, and for the moment may be put aside.
There were many classes even among the humanity, and the manner in which these distributed themselves over the Earth-chain needs some explanation.
It is the general rule that those who have attained the highest possible in any chain on any globe, in any root-race, are not born into the beginning of the next chain, globe or race, respectively.

The earlier stages are always for the backward entities, and only when they have already passed through a good deal of evolution and are beginning to approach the level of those others who had done better, do the latter descend into incarnation and join them once more.

That is to say, almost the earlier half of any period of evolution, whether it be a race, a globe or a chain, seems to be devoted to bringing the backward people up to nearly the level of those who have got on better; then these latter also (who, in the meantime, have been resting in great enjoyment in the mental world) descend into incarnation along with the others, and they press on together until the end of the period.
Thus the first of the egos from the Moon who entered the Earth-chain were by no means the most advanced.

Indeed they may be described as the least advanced of those who had succeeded in attaining humanity--the animal-men.
Coming as they did into a chain of new globes, freshly aggregated, they had to establish the forms in all the different kingdoms of Nature.